Chapter 9: Energy in a Cell · 9.1 SECTION PREVIEW Objectives Explain why organisms need a supply...
Transcript of Chapter 9: Energy in a Cell · 9.1 SECTION PREVIEW Objectives Explain why organisms need a supply...
What Yoursquoll Learn You will recognize why organ-
isms need a constant supply ofenergy and where that energycomes from
You will identify how cells storeand release energy as ATP
You will describe the pathwaysby which cells obtain energy
You will compare ATP produc-tion in mitochondria and inchloroplasts
Why Itrsquos ImportantEvery cell in your body needsenergy in order to function The energy your cells store is the fuel for basic body functionssuch as walking and breathing
Energy in a CellEnergy in a Cell
Johann SchumacherPeter Arnold Inc
Visit tobull study the entire chapter
onlinebull access Web Links for more
information and activities oncell energy
bull review content with theInteractive Tutor and self-check quizzes
This squirrel is eating seeds produced by the conifer Theconifer traps light energy andstores it in the bonds of certainmolecules for later use How dothe squirrelrsquos cells which cannottrap light energy use the mole-cules in the seeds to supplyenergy for the squirrel
Understandingthe Photo
220
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91SECTION PREVIEWObjectivesExplain why organismsneed a supply of energyDescribe how energy isstored and released by ATP
Review Vocabularyactive transport movement
of materials through amembrane against a concentration gradientrequires energy from the cell (p 199)
New VocabularyATP (adenosine triphosphate)
ADP (adenosine diphosphate)
91 THE NEED FOR ENERGY 221
Why ATPUsing an Analogy A spring stores energywhen it is compressed When the com-pressed spring is released energy also isreleased energy that sends this smiley-faced toy flying into the air Likethis coiled spring chemical bondsstore energy that can be releasedwhen the bond is broken Just assome springs are tighter than oth-ers some chemical bonds storemore energy than othersSummarize Scan this section and make a list of general ways in which cells use energy
The Need for Energy
Stored energy
Cell EnergyEnergy is essential to life All living
organisms must be able to obtain energyfrom the environment in which they livePlants and other green organisms are ableto trap the light energy in sunlight andstore it in the bonds of certain moleculesfor later use Other organisms such as thepanda shown in Figure 91 cannot usesunlight directly Instead they eat greenplants In that way they obtain the energystored in plants
Work and the need for energyYoursquove learned about several cell
processes that require energy Activetransport cell division movement of fla-gella or cilia and the production trans-port and storage of proteins are someexamples You can probably come up withother examples of biological work such asmuscles contracting during exercise your
Figure 91Because this pandacannot trap thesunrsquos energy foruse in its body iteats bambooMolecules in bam-boo leaves containenergy in theirchemical bondsSome of thosemolecules supplyenergy for thepanda
(tl tr)Aaron Haupt (bl)Tom McHughPhoto Researchers
Objective 203 Investigatethe cell as a living system including Energy use andrelease in biochemical reactions
North Carolina Objectives
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heart pumping and your brain control-ling your entire body This work can-not be done without energy
When you finish strenuous physi-cal exercise such as running crosscountry your body needs a quicksource of energy so you may eat agranola bar On a cellular level thereis a molecule in your cells that is aquick source of energy for anyorganelle in the cell that needs it
This energy is stored in the chemicalbonds of the molecule and can beused quickly and easily by the cell
The name of this energy moleculeis adenosine triphosphate (uh DEH
nuh seen bull tri FAHS fayt) or ATP forshort ATP is composed of an adeno-sine molecule with three phosphategroups attached Recall that phos-phate groups are charged particlesand remember that particles with thesame charge do not like being tooclose to each other
Forming and Breaking Down ATP
The charged phosphate groups actlike the positive poles of two mag-nets If like poles of a magnet areplaced next to each other it is diffi-cult to force the magnets togetherLikewise bonding three phosphategroups to form adenosine triphos-phate requires considerable energyWhen only one phosphate groupbonds a small amount of energy isrequired and the chemical bond doesnot store much energy This mole-cule is called adenosine monophos-phate (AMP) When a secondphosphate group is added moreenergy is required to force the twogroups together This molecule iscalled adenosine diphosphate orADP An even greater amount ofenergy is required to force a thirdcharged phosphate group closeenough to the other two to form abond When this bond is brokenenergy is released
The energy of ATP becomes avail-able to a cell when the molecule is broken down In other words whenthe chemical bond between the sec-ond and third phosphate groups inATP is broken energy is released andthe resulting molecule is ADP At this
222 ENERGY IN A CELLMel VictorThe Stock Shop
mono- di- tri- fromthe Greek wordsmono and di andthe Latin word trimeaning ldquoonerdquoldquotwordquo and ldquothreerdquorespectivelyAdenosine triphos-phate contains threephosphate groups
Recognize Cause and EffectWhy is fat the choiceHumans store their excess energy as fat rather than as car-bohydrates Why is this From an evolutionary and efficiencypoint of view fats are better for storage than carbohydrates Find out why
Solve the ProblemThe following facts compare certain characteristics of fats andcarbohydratesA When broken down by the body each six-carbon molecule
of fat yields 51 ATP molecules Each six-carbon carbo-hydrate molecule yields 36 ATP molecules
B Carbohydrates bind and store water The metabolism ofwater yields no ATP Fat has no water bound to it
C An adult who weighs 70 kg can survive on the energyderived from stored fat for 30 days without eating Thesame person would have to weigh nearly 140 kg to survive30 days on stored carbohydrates
Thinking Critically1 Analyze From an ATP production viewpoint use fact B
to make a statement regarding the efficiency of fats vs carbohydrates
2 Define Operationally Explain why the average weightfor humans is close to 70 kg and not 140 kg
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point ADP can form ATP again bybonding with another phosphategroup This process creates a renew-able cycle of ATP formation andbreakdown Figure 92A illustratesthe chemical reactions that areinvolved in the cycle
The formationbreakdown recy-cling activity is important because itrelieves the cell of having to store allof the ATP it needs As long as phos-phate groups are available the cellcan make more ATP Another benefitof the formationbreakdown cycle isthat ADP also can be used as anenergy source Although most cellfunctions require the amount ofenergy in ATP some cell functions donot require as much energy and canuse the energy stored in ADP Readthe Problem-Solving Lab on the oppo-site page and think about how thehuman body stores energy
How cells tap into the energystored in ATP
When ATP is broken down and theenergy is released as shown in Figure 92B the energy must be cap-tured and used efficiently by cellsOtherwise it is wasted ATP is a smallmolecule Many proteins have a spe-cific site where ATP can bind Thenwhen the phosphate bond is brokenand the energy released the cell canuse the energy for activities such asmaking a protein or transporting mol-ecules through the plasma membraneThis cellular process is similar to theway energy in batteries is used by aradio Batteries sitting on a table are oflittle use if the energy stored withinthe batteries cannot be accessedWhen the batteries are snapped intothe holder in the radio the radio thenhas access to the stored energy andcan use it When the energy in the
91 THE NEED FOR ENERGY 223
ADP
ADP
ATP
Adenosine
Protein
P P P
P
P
P
Adenosine P P
Adenosine triphosphate (ATP)
Adenosine diphosphate (ADP)
+ Energy
The addition and release of a phosphate group onadenosine diphosphate creates a cycle of ATP forma-tion and breakdown
A To access the energy stored in ATP proteins bind ATPand uncouple the phosphate group The ADP that isformed is released and the protein binding site canonce again bind ATP
B
Figure 92The formation and breakdown of ATP is cyclic
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Understanding Main Ideas1 Identify cellular processes that need energy
from ATP
2 How does ATP store energy
3 How can ADP be ldquorecycledrdquo to form ATP again
4 How do proteins in your cells access the energystored in ATP
5 List three biological activities that require energy
Thinking Critically6 Phosphate groups in ATP repel each other because
they have negative charges What charge mightbe present in the ATP binding site of a protein toattract ATP
7 Get the Big Picture How does an animal accessthe energy in sunlight For more help refer toGet the Big Picture in the Skill Handbook
SKILL REVIEWSKILL REVIEW
224 ENERGY IN A CELL(t)Dr KS KimPeter Arnold Inc (b)National Geographic Society Image Collection
Figure 93ATP fuels the cellular activitythat drives the organism DefineOperationally What organelles do these cells or organismsuse for movement
Some organisms(left) use energyfrom ATP to move
C
batteries has been used the batteriescan be taken out recharged andreplaced in the holder In a similarfashion in a cell when ATP has beenbroken down to ADP the ADP isreleased from the binding site in theprotein and the binding site may thenbe filled by another ATP molecule
Uses of Cell EnergyYou can probably think of hun-
dreds of physical activities thatrequire energy but energy is equallyimportant at the cellular level
Making new molecules is one waythat cells use energy Some of thesemolecules are enzymes Other mole-cules build membranes and cellorganelles Cells use energy tomaintain homeostasis Kidneys useenergy to move molecules and ions in order to eliminate waste substances while keeping needed substances in the bloodstreamFigure 93 shows several ways thatcells use energy
List three cellularactivities that require energy
Stained TEM Magnification 18 000
Nerve cells transmitimpulses by usingATP to power theactive transport ofcertain ions
A
Fireflies and many marine organisms such asthe jellyfish shown here produce light by aprocess called bioluminescence The light resultsfrom a chemical reaction that is powered by thebreakdown of ATP
B
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Photosynthesis Trapping the Sunrsquos Energy
92 PHOTOSYNTHESIS TRAPPING THE SUNrsquoS ENERGY 225
SECTION PREVIEWObjectivesRelate the structure ofchloroplasts to the events inphotosynthesisDescribe light-dependentreactionsExplain the reactions and products of the light-independent Calvin cycle
Review Vocabularychloroplast cell organelle
that captures lightenergy and producesfood to store for lateruse (p 184)
New Vocabularyphotosynthesislight-dependent reactionslight-independent reactionspigmentchlorophyllelectron transport chainNADP+photolysisCalvin cycle
92
Photosynthesis Make the following Foldable to help you illustrate what happens during each phase of photosynthesis
Fold a vertical sheet of paper in half from top to bottom
Fold in half from side to side with the fold at the top
STEP 1 STEP 2
1st PhaseLight-
Dependent
2nd PhaseLight-
Independent
Unfold the paper once Cut only the fold of the top flap to make two tabs
Turn the paper vertically and label on the front tabs as shown
STEP 3 STEP 4
Compare and Contrast As you read Section 92 compare and contrast the two phases of photosynthesis under the appropriate tab
Trapping Energy from SunlightTo use the energy in sunlight the cells of green organisms must trap light
energy and store it in a manner that is readily usable by cell organellesmdashinthe chemical bonds of ATP However light energy is not available 24 hoursa day so the cell must also store some of the energy for use during the darkhours The process that uses the sunrsquos energy to make simple sugars is calledphotosynthesis These simple sugars are then converted into complex car-bohydrates such as starches which store energy
Photosynthesis happens in two phases The light-dependent reactionsconvert light energy into chemical energy The molecules of ATP produced in the light-dependent reactions are then used to fuel the light-independent reactions that produce simple sugars The generalequation for photosynthesis is written as follows
6CO2 6H2O rarr C6H12O6 6O2
The BioLab at the end of this chapter can be performed to study whatfactors influence the rate of photosynthesis
photosynthesisfrom the Greekwords photomeaning ldquolightrdquoand syntithenaimeaning ldquoto puttogetherrdquoPhotosynthesisputs togethersugar moleculesusing water car-bon dioxide andenergy from light
Objective 205 Investigate and analyze the bioener-getic reactions Photosynthesis
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ExperimentSeparating PigmentsChromatography is an impor-tant diagnostic tool In thisexperiment you will use paperchromatography to separatedifferent pigments from plantleaves
Procedure Obtain a pre-made plant solution from your teacher Place a few drops 2 cm high on a 5-cm 14-cm strip of
filter paper Let it dry Make sure a small colored spot isvisible
Pour rubbing alcohol in a 100-mL beaker to a depth of1 cm
$ Place the filter paper into the beaker The filter papershould touch the alcohol but the dot should not Hold it in place 15 minutes and observe what happens
Analysis 1 Explain What did you observe as the solvent moved
up the filter paper2 Infer Why did you see different colors at different
locations on the filter paper
(t)Matt Meadows (b)James Westwater
Figure 94The red yellow andpurple pigments arevisible in the autumnRecognize Cause andEffect Why canrsquot yousee these colors dur-ing the summer
226 ENERGY IN A CELL
The chloroplast and pigmentsRecall that the chloroplast is the
cell organelle where photosynthesisoccurs It is in the membranes of thethylakoid discs in chloroplasts that thelight-dependent reactions take place
To trap the energy in the sunrsquos light the thylakoid membranes con-tain pigments molecules that absorbspecific wavelengths of sunlight Pig-ments are arranged within the thy-lakoid membranes in clusters known asphotosystems Although a photosys-tem contains several kinds of pig-ments the most common ischlorophyll Chlorophyll absorbsmost wavelengths of light exceptgreen Because chlorophyll cannotabsorb this wavelength it is reflectedgiving leaves a green appearance Inthe fall trees stop producing chloro-phyll in their leaves Other pigmentsbecome visible giving leaves like thosein Figure 94 a wide variety of colorsThe MiniLab on this page will allowyou to separate the pigments in a leafRead the Connection to Chemistry at theend of this chapter to find out moreabout biological pigments
Light-DependentReactions
The first phase of photosynthesisrequires sunlight As sunlight strikesthe chlorophyll molecules in a photo-system of the thylakoid membrane theenergy in the light is transferred toelectrons These highly energized orexcited electrons are passed fromchlorophyll to an electron transportchain a series of proteins embedded inthe thylakoid membrane Figure 95summarizes this process
Each protein in the chain passesenergized electrons along to the nextprotein similar to a bucket brigade inwhich a line of people pass a bucket of
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92 PHOTOSYNTHESIS TRAPPING THE SUNrsquoS ENERGY 227
water from person to person to fight afire At each step along the transportchain the electrons lose energy just assome of the water might be spilledfrom buckets in the fire-fightingchain This ldquolostrdquo energy can be usedto form ATP from ADP or to pumphydrogen ions into the center of thethylakoid disc
After the electrons have traveleddown the electron transport chainthey are re-energized in a secondphotosystem and passed down a sec-ond electron transport chain At thebottom of this chain the electronsare still very energized So that thisenergy is not wasted the electronsare transferred to the stroma of thechloroplast To do this an electroncarrier molecule called NADP
(nicotinamide adenine dinucleotidephosphate) is used NADP cancombine with two excited electronsand a hydrogen ion (H) to becomeNADPH NADPH does not use theenergy present in the energized elec-trons it simply stores the energyuntil it can transfer it to the stromaThere NADPH will play an impor-tant role in the light-independentreactions
Explain how energyfrom electrons is released
Restoring electronsRecall that at the beginning of
photosynthesis electrons are lostfrom chlorophyll molecules whenlight is absorbed If these electronsare not replaced the chlorophyll willbe unable to absorb additional lightand the light-dependent reactionswill stop as will the production ofATP To replace the lost electronsmolecules of water are split in thefirst photosystem This reaction iscalled photolysis (fo TAH luh sis)For every water molecule that is
Light-Dependent Reactions
Light energy
Chlorophyllpasses energy
down through theelectron transport chain
Energized electrons provideenergy that
transfers to chlorophyll
Sun
splitsH2O
bonds to ADP
formingATPH+
oxygenreleased
for use in thelight-independent reactions
NADP+
NADPH
P
Figure 95Chlorophyll molecules absorb light energyand energize electrons for producing ATPand NADPH
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split one half molecule of oxygentwo electrons and two hydrogenions are formed as shown inFigure 96 The oxygen producedby photolysis is released into the airand supplies the oxygen we breatheThe electrons are returned tochlorophyll The hydrogen ions arepumped into the thylakoid wherethey accumulate in high concentra-tion Because this difference in con-centration forms a concentrationgradient across the membrane H
ions diffuse out of the thylakoid andprovide energy for the production ofATP This coupling of the move-ment of H ions to ATP productionis called chemiosmosis (keh mee ozMOH sis) The MiniLab on this pageshows how the steps of photosynthe-sis were traced
Light-IndependentReactions
The second phase of photosynthe-sis does not require light It is calledthe Calvin cycle which is a series ofreactions that use carbon dioxide toform sugars The Calvin cycle takesplace in the stroma of the chloroplastas shown in Figure 97
228 ENERGY IN A CELL
Sun
Chlorophyll O2 + 2H+
H2O
2endash
H2O 2H+ + O2 + 2endash 1
2
1
2
Figure 96In photolysis a molecule of water is split toreplace electrons lost from chlorophyll H+
for chemiosmosis and oxygen Infer Howmany molecules of water must be splitto make a molecule of oxygen gas
Formulate ModelsUse Isotopes to UnderstandPhotosynthesis C B van Nieldemonstrated that photosynthesis is a light-dependent reaction inwhich the O2 comes from waterOther scientists confirmed his find-ings by using radioactive isotopes ofoxygen as tracers Radioactive tracersare used to follow a particular moleculethrough a chemical reaction
Procedure Study the following general equation that resulted from
the van Niel experimentCO2 2H2O rarr CH2O H2O O2
Radioactive water water tagged with an isotope of oxygenas a tracer (shown by the ) was used Note where thetagged oxygen ends up on the right side of the equation
Assume that the experiment was repeated but this time aradioactive tag was put on the oxygen in CO2
$ Using materials provided by your teacher model what youpredict the appearance of the results would be Yourmodel must include a ldquotagrdquo to indicate the oxygen isotopeon the left side of the arrow as well as where it ends upon the right side of the arrow
You also must use labels or different colors in your modelto indicate what happens to the carbon and hydrogen
Analysis1 Explain How can an isotope be used as a tag2 Use Models Using your model predict what happens to
a all oxygen molecules that originated from carbon dioxideb all carbon molecules that originated from carbon dioxidec all hydrogen molecules that originated from water
van Niel
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92 PHOTOSYNTHESIS TRAPPING THE SUNrsquoS ENERGY 229
C C C C C
C
C C C C C C
C C C
C C C
C C CC C C
C C C
C C C C C C
C C C
(Sugars and other carbohydrates)
ADP +
ADP + ATP
ATP
NADP+
NADPH
(RuBP)
(CO2)
(Unstable intermediate)
(PGAL)(PGAL)
(PGAL)
CalvinCycle
P
P
Formation of 3-carbon moleculesThe six-carbon sugarformed in Step Aimmediately splits to form two three-carbonmolecules
BB
Use of ATP andNADPH A series of reactions involving ATP and NADPH from the light-dependent reactionsconverts the three-carbonmolecules into phospho-glyceraldehyde (PGAL)three-carbon sugars withhigher energy bonds
CC
Sugar production One outof every six molecules of PGALis transferred to the cytoplasmand used in the synthesis ofsugars and other carbohydratesAfter three rounds of the cyclesix molecules of PGAL areproduced
DD
RuBP is replenishedFive molecules of PGALeach with three carbonatoms produce threemolecules of the five-carbon RuBP Thisreplenishes the RuBP thatwas used up and the cyclecan continue
EE
Carbon fixationThe carbon atom from CO2bonds with a five-carbonsugar called ribulosebiphosphate (RuBP) toform an unstable six-carbon sugar
AA
The stroma in chloroplastshosts the Calvin cycle
Color-enhanced TEMMagnification 6300
The Calvin CycleFigure 97The Calvin cycle takes the carbon in CO2 adds it to one mole-cule of RuBP and forms sugars through a series of reactionsin the stroma of chloroplasts The NADPH and ATP producedduring the earlier light-dependent reactions are importantmolecules for this series of reactions Critical Thinking Whyis the Calvin cycle in plants directly and indirectlyimportant to animals
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Understanding Main Ideas1 Why do you see green when you look at a leaf on
a tree Why do you see other colors in the fall
2 How do the light-dependent reactions of photosynthesis relate to the Calvin cycle
3 What is the function of water in photosynthesisExplain the reaction that achieves this function
4 How does the electron transport chain transferlight energy in photosynthesis
Thinking Critically5 In photosynthesis is chlorophyll considered a reac-
tant a product or neither How does the role ofchlorophyll compare with the roles of CO2 and H2O
6 Get the Big Picture Identify the parts of thechloroplast in which the various steps of photo-synthesis take place For more help refer to Getthe Big Picture in the Skill Handbook
SKILL REVIEWSKILL REVIEW
230 ENERGY IN A CELLCORBISBettmann-UPI
The Calvin cycleThe Calvin cycle named after
Melvin Calvin who worked out thedetails of the reactions is called a cyclebecause one of the last moleculesformed in the series of chemical reac-tions is also one of the moleculesneeded for the first reaction of thecycle Therefore one of the productscan be used again to continue the cycle
You have learned that in the elec-tron transport chain an energizedelectron is passed from protein toprotein and the energy is releasedslowly You can imagine that making acomplex carbohydrate from a mole-cule of CO2 would be a large task fora cell so the light-independent reac-tions in the stroma of the chloroplastbreak down the complicated processinto small steps
At the beginning of the Calvincycle one molecule of carbon diox-ide is added to one molecule ofRuBP to form a six-carbon sugarThis step is called carbon fixationbecause carbon is ldquofixedrdquo into a six-carbon sugar In a series of reactionsthe sugar breaks down and is eventu-ally converted to two three-carbonsugars called phosphoglyceralde-hyde or PGAL After three roundsof the cycle with each round fixingone molecule of CO2 six moleculesof PGAL are produced Five of thesemolecules are rearranged to formthree molecules of RuBP the start-ing material The sixth molecule ofPGAL is available to the organismfor making sugars complex carbo-hydrates and other organic com-pounds As you will see in the nextsection PGAL is important to allorganisms because it plays a role incellular respiration
Biochemist
I f you are curious about whatmakes plants and animals grow
and develop consider a career as abiochemist The basic research ofbiochemists seeks to understandhow processes in an organism workto ensure the organismrsquos survival
Skills for the JobA bachelorrsquos degree in chemistry or
biochemistry will qualify you to be a lab assistant For a more involved position you will need a masterrsquos degree advanced research requires a PhD Somebiochemists work with genes to create new plants and newchemicals from plants Others research the causes and curesof diseases or the effects of poor nutrition Still othersinvestigate solutions for urgent problems such as findingbetter ways of growing storing and caring for crops
To find out more about careers in related fieldsvisit ncbdolglencoecomcareers
ncbdolglencoecomself_check_quiz
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93SECTION PREVIEWObjectivesCompare and contrastcellular respiration andfermentationExplain how cells obtainenergy from cellular respiration
Review Vocabularymitochondria cell organ-
elles that transformenergy for the cell (p 185)
New Vocabularycellular respirationanaerobicaerobicglycolysiscitric acid cyclelactic acid fermentationalcoholic fermentation
anaerobic fromthe Greek wordsan meaningldquowithoutrdquo andaeros meaningldquoairrdquo Anaerobicorganisms can livewithout oxygen
93 GETTING ENERGY TO MAKE ATP 231
What happens to sugarsUsing Prior Knowledge Youknow that the chlorophyll ingreen plants is the key to photo-synthesis and that sugars are pro-duced You also know that yourbody needs energy to surviveSugars can be broken down incells to yield large amounts ofenergy But your cells canrsquot con-vert light energy to sugars Whatwill you do Fortunately the cellsof all organisms can use the sug-ars made by plants during theCalvin cycle By eating plantmaterial animals too can accessthe sunrsquos energyIdentify In which organelle are sugars converted to ATP
Getting Energy to Make ATP
Michael KellerCORBIS
Cellular RespirationThe process by which mitochondria break down food molecules to pro-
duce ATP is called cellular respiration There are three stages of cellularrespiration glycolysis the citric acid cycle and the electron transport chainThe first stage glycolysis is anaerobicmdashno oxygen is required The lasttwo stages are aerobic and require oxygen to be completed
GlycolysisGlycolysis (gli KAH lih sis) is a series of chemical reactions in the cyto-
plasm of a cell that break down glucose a six-carbon compound into twomolecules of pyruvic (pie RUE vik) acid a three-carbon compoundBecause two molecules of ATP are used to start glycolysis and only fourATP molecules are produced glycolysis is not very effective producingonly two ATP molecules for each glucose molecule broken down
In the electron transport chain of photosynthesis an electron carriercalled NADP was described as carrying energized electrons toanother location in the cell for further chemical reactions Glycolysisalso uses an electron carrier called NAD (nicotinamide adenine di-nucleotide) NAD forms NADH when it accepts two electrons
Objective 205 Investigate and analyze the bioener-getic reactions Aerobic Respiration Anaerobic Respiration
North Carolina Objectives
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Notice in Figure 98 that twomolecules of PGAL are formed dur-ing glycolysis Recall that PGALalso forms in the Calvin cycle ThePGAL made during photosynthesiscan enter the glycolysis pathway andlead to the formation of ATP andorganic molecules
Following glycolysis the pyruvicacid molecules move into the mito-chondria the organelles that transformenergy for the cell In the presence ofoxygen two more stages complete cel-lular respiration the citric acid cycleand the electron transport chain of themitochondrion Before these twostages can begin however pyruvic acidundergoes a series of reactions in whichit gives off a molecule of CO2 and com-bines with a molecule called coenzymeA to form acetyl-CoA The reactionwith coenzyme A produces a molecule
of NADH and H These reactionsare shown in Figure 99
The citric acid cycleThe citric acid cycle also called
the Krebs cycle is a series of chemicalreactions similar to the Calvin cyclein that the molecule used in the firstreaction is also one of the end prod-ucts Read Figure 910 to study thecitric acid cycle
For every turn of the cycle one mol-ecule of ATP and two molecules of car-bon dioxide are produced Twoelectron carriers are used NAD andFAD (flavin adenine dinucleotide) Atotal of three NADH three H ionsand one FADH2 are formed The elec-tron carriers each pass two energizedelectrons along to the electron trans-port chain in the inner membrane ofthe mitochondrion
232 ENERGY IN A CELL
C C C CC C C P
C C C
C C C
C C CPC C
ENERGY ENERGY
2ATP2ADP
4ADP + 4 P
2NAD+2PGAL
Glucose
4ATP
2NADH + 2H+
2 Pyruvicacid
C C C C C C C C C CC
NAD+
CO2
NADH + H+
Pyruvicacid
Outside themitochondrion
Mitochondrialmembrane
Coenzyme A
Pyruvicacid
Inside themitochondrion
Intermediateby-product
- CoAAcetyl-CoA
+
Figure 98Glycolysis breaks downa molecule of glucoseinto two molecules ofpyruvic acid In theprocess it forms a netof two molecules ofATP two molecules ofNADH and two hydro-gen ions
Figure 99Before the citric acidcycle and electron trans-port chain begin pyruvicacid undergoes a seriesof reactions InferWhat products areformed as a result ofthe reactions withinthe mitochondrion
0231-0243 C9S3 BDOL-829900 8404 500 AM Page 232
The Citric Acid CycleFigure 910The citric acid cycle breaks down a molecule ofacetyl-CoA and forms ATP and CO2 The electroncarriers NAD and FAD pick up energized electronsand pass them to the electron transport chain inthe inner mitochondrial membrane Critical ThinkingHow many CO2 molecules are produced for everyglucose molecule that entered the cellular respira-tion pathways
93 GETTING ENERGY TO MAKE ATP 233
P
NAD+
NAD+
NAD+
FADH2FAD
C C
NADH + H+
NADH + H+
ATP
ADP +
(Acetyl-CoA)
(Oxaloacetic acid)(Citric acid)
CitricAcidCycle
O O(CO2)
O O(CO2)
NADH + H+
C C C C
C C C C
C C C C
C C C C
C C C C C
C
C C C C C
C
C
Formation of the second CO2 Anothermolecule of CO2 is released forming a four-carboncompound One molecule of ATP and a moleculeof NADH are also produced
CC
Citric acid The two-carboncompound acetyl-CoA reactswith a four-carbon compoundcalled oxaloacetic acid to formcitric acid a six-carbonmolecule
AA Formation of CO2 A moleculeof CO2 is formed reducing theeventual product to a five-carboncompound In the process amolecule of NADH and H+ isproduced
BB
Profs P Motta amp T NaguroScience Photo LibraryCustom Medical Stock Photo
Recycling of oxaloacetic acid The four-carbon molecule goesthrough a series of reactions in which FADH2 NADH and H+
are formed The carbon chainis rearranged and oxaloaceticacid is again made availablefor the cycle
DD
The mitochondria hostthe citric acid cycle
Magnification unavailable
0231-0243 C9S3 BDOL-829900 8404 500 AM Page 233
The electron transport chainThe electron transport chain in
the inner membrane of the mito-chondrion is very similar to the elec-tron transport chains of thethylakoid membrane in the chloro-plasts of plant cells during photo-synthesis NADH and FADH2deliver energized electrons at thetop of the chain The electrons arepassed from protein to proteinwithin the membrane slowly releas-ing their energy in steps Some ofthat energy is used directly to formATP some is used by an enzyme topump H ions into the center of themitochondrion Consequently themitochondrion inner membranebecomes positively charged becauseof the high concentration of posi-tively charged hydrogen ions At thesame time the exterior of the mem-brane is negatively charged whichfurther attracts hydrogen ions Thegradient of H ions that resultsacross the inner membrane of themitochondrion provides the energy
for ATP production just as it does in the chemiosmotic process that takes place at the thylakoid mem-branes in the chloroplasts Figure 911summarizes the electron transportchain and the formation of ATP
The final electron acceptor at thebottom of the chain is oxygen whichreacts with four hydrogen ions (4H)and four electrons to form two mole-cules of water (H2O) This is why oxy-gen is so important to our bodiesWithout oxygen the proteins in theelectron transport chain cannot passalong the electrons If a protein cannotpass along an electron to oxygen itcannot accept another electron Veryquickly the entire chain becomesblocked and ATP production stops
Overall the electron transportchain adds 32 ATP molecules to thefour already produced Obviouslythe aerobic process of ATP produc-tion is very effective In the absenceof oxygen however an anaerobicprocess can produce small amountsof ATP to keep the cell from dying
234 ENERGY IN A CELL
H H
H
H
H
H
P
Electroncarrier proteins
Electronpathway
Space betweeninner and outer
membranes
Enzyme
ADP ATP
Innermembrane
Center ofmitochondrion
NAD
FAD
NADH
FADH2
4 H O2 4 electrons
H2O
H2O
e
Figure 911In the electron transportchain the carrier mole-cules NADH and FADH2give up electrons thatpass through a series ofreactions Oxygen is thefinal electron acceptor
0231-0243 C9S3 BDOL-829900 8404 501 AM Page 234
93 GETTING ENERGY TO MAKE ATP 235
FermentationThere are times such as during
heavy exercise when your cells arewithout oxygen for a short period oftime When this happens an anaero-bic process called fermentation fol-lows glycolysis and provides a meansto continue producing ATP until oxy-gen is available again There are twomajor types of fermentation lacticacid fermentation and alcoholic fer-mentation The table in Figure 912compares the two processes with res-piration Perform the Problem-SolvingLab shown here to further compareand contrast cellular respiration andfermentation
Infer when yourbody might perform fermentationreactions
Lactic acid fermentationYou know that under anaerobic con-
ditions the electron transport chainbacks up because oxygen is not present
Gerard VandystadtVandystadt AgencyPhoto Researchers
Figure 912Lactic acid and alcoholic fermentations are comparablein the production of ATP but compared to cellular respi-ration it is obvious that fermentation is far less efficientin ATP production This runnerrsquos muscles have beendepleted of oxygen and fermentation is taking place
Comparison of Fermentation to Cellular Respiration
Lactic Acid Alcoholic Cellular respiration
glucose glucose glucose
glycolysis (pyruvic acid) glycolysis (pyruvic acid) glycolysis (pyruvic acid)
carbon dioxide carbon dioxide
lactic acid alcohol water
2 ATP 2 ATP 36 ATP
Acquire InformationCellular respiration or fermentation The methods bywhich organisms derive ATP may differ however the resultthe production of ATP molecules is similar
Solve the ProblemStudy the table in Figure 912 and evaluate cellular respirationlactic acid fermentation and alcoholic fermentation
Thinking Critically1 Describe Why does cellular respiration produce so much
more ATP than does fermentation2 Use Scientific Explanations Describe a situation when a
human would need to use more than one of the processeslisted above
3 Analyze Think of an organism that might generate ATPonly by fermentation and consider why fermentation is thebest process for the organism
0231-0243 C9S3 BDOL-829900 8404 501 AM Page 235
as the final electron acceptor AsNADH and FADH2 arrive at the chainfrom the citric acid cycle and glycolysisthey cannot release their energizedelectrons The citric acid cycle and gly-colysis cannot continue without asteady supply of NAD and FAD
The cell does not have a method toreplace FAD during anaerobic condi-tions however NAD can bereplaced through lactic acid fermenta-tion Lactic acid fermentation is oneof the processes that supplies energywhen oxygen is scarce Two moleculesof pyruvic acid produced in glycolysisuse NADH to form two molecules oflactic acid This releases NAD to beused in glycolysis allowing two ATPmolecules to be formed for each glu-cose molecule The lactic acid is trans-ferred from muscle cells where it isproduced during strenuous exerciseto the liver that converts it back topyruvic acid The lactic acid thatbuilds up in muscle cells results inmuscle fatigue
Alcoholic fermentationAnother type of fermentation
alcoholic fermentation is used by yeast cells and some bacteria toproduce CO2 and ethyl alcoholWhen making bread like that shownin Figure 913 yeast cells produceCO2 that forms bubbles in the doughEventually the heat of the oven killsthe yeast and the bubble pockets areleft to lighten the bread You can dothe MiniLab on this page to studyalcoholic fermentation in apple juice
236 ENERGY IN A CELL
Figure 913Alcoholic fermentation by the yeast in breaddough produces CO2 bubbles that raise thedough Think Critically What happens tothe CO2
PredictDetermine if Apple Juice Ferments Some organ-isms such as yeast can breakdown food molecules and syn-thesize ATP when no oxygen isavailable When food is avail-able yeast carry out alcoholicfermentation producing CO2Thus the production of CO2 inthe absence of oxygen can beused to judge whether alcoholicfermentation is taking place
Procedure Carefully study the diagram
and set up the experimentas shown
Hold the test tube in abeaker of warm (not hot)water and observe
Analysis1 Interpret Data What were the gas bubbles that came
from the plastic pipette2 Hypothesize What would happen to the rate of bubbles
given off if more yeast were present in the mixture3 Analyze Why was the test tube placed in warm water4 Draw Conclusions Was the process you demonstrated
aerobic or anaerobic Explain
Yeast andapple juice
Plastic pipette
Water
Test tube
Metalwashers
Matt Meadows
0231-0243 C9S3 BDOL-829900 8404 502 AM Page 236
ComparingPhotosynthesis andCellular Respiration
The production and breakdownof food molecules are accomplishedby distinct processes that bear cer-tain similarities Both photosynthe-sis and cellular respiration useelectron carriers and a cycle ofchemical reactions to form ATPBoth use electron transport chainsto form ATP and to create a chemi-cal and a concentration gradient ofH within a cell This hydrogen iongradient can be used to form ATP bychemiosmosis
However despite using such simi-lar tools the two cellular processesaccomplish quite different tasksPhotosynthesis produces high-energycarbohydrates and oxygen from thesunrsquos energy whereas cellular respira-tion uses oxygen to break down car-bohydrates to form ATP andcompounds that provide less energyAlso one of the end products of cel-lular respiration is CO2 which is oneof the beginning products for photo-synthesis The oxygen produced dur-ing photosynthesis is a criticalmolecule necessary for cellular respi-ration Table 91 compares thesecomplementary processes
Understanding Main Ideas1 Compare the ATP yields of glycolysis the citric
acid cycle and the electron transport chain2 How do alcoholic fermentation and lactic acid fer-
mentation differ3 How is most of the ATP from aerobic respiration
produced4 Why is lactic acid fermentation important to the
cell when oxygen is scarce5 How many ATP molecules are produced after the
electrons go down the electron transport chain
Thinking Critically6 Compare the energy-producing processes in a
joggerrsquos leg muscles with those of a sprinterrsquosleg muscles Which is likely to build up more lactic acid Explain
7 Get the Big Picture How are the chemical reac-tions of photosynthesis and cellular respirationconnected What is the significance of this con-nection For more help refer to Get the BigPicture in the Skill Handbook
SKILL REVIEWSKILL REVIEW
93 GETTING ENERGY TO MAKE ATP 237(l)file photo (r)George Robbins
Table 91 Comparison of Photosynthesis and Cellular Respiration
Photosynthesis Cellular Respiration
Food synthesized Food broken down
Energy from sun stored in glucose Energy of glucose released
Carbon dioxide taken in Carbon dioxide given off
Oxygen given off Oxygen taken inProduces sugars Produces CO2from PGAL and H2ORequires Does notlight require lightOccurs only in Occurs in allpresence of living cellschlorophyll
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0231-0243 C9S3 BDOL-829900 8404 502 AM Page 237
What factors influence photosynthesis
ProblemHow do different wavelengths of light that a plant receivesaffect its rate of photosynthesis
ObjectivesIn this BioLab you will Observe photosynthesis in an aquatic organism Measure the rate of photosynthesis Research the wavelengths of various colors of light Observe how various wavelengths of light influence the
rate of photosynthesis Use the Internet to collect and compare data from other
students
Materials1000-mL beaker lamp with reflector andthree Elodea plants 150-watt bulbstring 025 sodium hydrogenwashers carbonate (baking soda) colored cellophane solution
assorted colors watch with second hand
Safety PrecautionsCAUTION Always wear goggles in the lab
Skill HandbookIf you need help with this lab refer to the Skill Handbook
1 Construct a basic setup like the one shown here2 Create a data table to record your measurements Be sure
to include a column for each color of light you will inves-tigate and a column for the control
3 Place the Elodea plants in the beaker thencompletely cover them with water Addsome of the baking soda solution The solu-tion provides CO2 for the aquarium plantsBe sure to use the same amount of waterand solution for each trial
PROCEDUREPROCEDURE
PREPARATIONPREPARATIONBefore YouBegin
Oxygen is one of the prod-ucts of photosynthesisBecause oxygen is onlyslightly soluble in wateraquatic plants such asElodea give off visiblebubbles of oxygen as theycarry out photosynthesis By measuring the rate atwhich bubbles form youcan measure the rate ofphotosynthesis
Matt Meadows
0231-0243 C9S3 BDOL-829900 8404 504 AM Page 238
ANALYZE AND CONCLUDEANALYZE AND CONCLUDE
93 GETTING ENERGY TO MAKE ATP 239
1 Interpret Observations From wheredid the bubbles of oxygen emerge
2 Make Inferences Explain how counting bubbles measures the rate of photosynthesis
3 Use the Internet Look up the wave-lengths of the colors of light you usedMake a graph of your data and dataposted by other students with the rateof photosynthesis per minute plottedagainst the wavelengths of light youtested for both the control and experi-mental setups Write a sentence or twoexplaining the graph
4 Why was it important to use the same amount of sodiumhydrogen carbonate in each trialERROR ANALYSIS
4 Conduct a control by directing the lamp (without col-ored cellophane) on the plant and noticing when you seethe bubbles
5 Observe and record the number of oxygen bubbles thatElodea generates in five minutes
6 Cover the lamp with a piece of colored cellophane andrepeat steps 4 and 5
7 Repeat steps 4 and 5 with a different color of cellophane8 Go to to post
your data9 Return plant material to an
aquarium to prevent it from drying outCLEANUP AND DISPOSAL
Bubbles observed in five minutes
Color 1 Color 2Control
Data Table
Find this BioLab using the link below and postyour data in the data table provided for thisactivity Using the additional data from otherstudents on the Internet analyze the com-bined data and expand your graph
ncbdolglencoecominternet_lab
ncbdolglencoecominternet_lab
Runk-SchoenbergerGrant Heilman Photography
0231-0243 C9S3 BDOL-829900 8404 508 AM Page 239
240 ENERGY IN A CELL
Plant Pigments
In photosynthesis light energy is converted intochemical energy To begin the process light is
absorbed by colorful pigment molecules containedin chloroplasts
A pigment is a substance that can absorb spe-cific wavelengths of visible light You can observethe colors of the various wavelengths of light byletting sunlight pass through a prism to create aldquorainbowrdquo or spectrum that has red light on oneend violet on the other and orange yellowgreen blue and indigo light in between
Every photosynthetic pigment is distinctive inthat it absorbs specific wavelengths in the visiblelight spectrum
Chlorophylls a and b The principal pig-ment of photosynthesis is chlorophyllChlorophyll exists in two forms designated as aand b Chlorophyll a and b both absorb light inthe violet to blue and the red to red-orange partsof the spectrum although at somewhat differentwavelengths These pigments also reflect greenlight which is why plant leaves appear green
When chlorophyll b absorbs light it transfersthe energy it acquires to chlorophyll a which thenfeeds that energy into the chemical reactions thatlead to the production of ATP and NADPH Inthis way chlorophyll b acts as an ldquoaccessoryrdquo pig-ment by making it possible for photosynthesis tooccur over a broader spectrum of light than wouldbe possible with chlorophyll a alone
Carotenoids and phycobilins Carotenoidsand phycobilins are other kinds of accessory pig-ments that absorb wavelengths of light differentfrom those absorbed by chlorophyll a and b andso extend the range of light that can be used forphotosynthesis
Carotenoids are yellow-orange pigmentsThey are found in all green plants but theircolor is usually masked by chlorophyll
Carotenoids are also found in cyanobacteria andin brown algae A particular carotenoid calledfucoxanthin gives brown algae their characteris-tic dark brown or olive green color
Phycobilins are blue and red Red algae gettheir distinctive blood-red coloration from phy-cobilins Some phycobilins can absorb wave-lengths of green violet and blue light whichpenetrate deep water One species of red algaethat contains these pigments is able to live atocean depths of 269 meters (8825 feet) Thealgaersquos pigments absorb enough of the incrediblyfaint light that penetrates to this depthmdashonly atiny percent of what is available at the waterrsquossurfacemdashto power photosynthesis
Think Critically How do you think accessorypigments may have influenced the spread of pho-tosynthetic organisms into diverse habitats such asthe deep sea
To find out more about pigments visit ncbdolglencoecomchemistry
(t)Robert CalentineVisuals Unlimited (inset)Dan GotshallVisuals Unlimited
Pigments color cyanobacteria(above) and red algae (inset)
LM Magnification 450
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Section 91Vocabulary(ADP) adenosine
diphosphate (p 222)(ATP) adenosine
triphosphate (p 222)
VocabularyCalvin cycle (p 228)chlorophyll (p 226)electron transport chain
(p 226)light-dependent
reactions (p 225)light-independent
reactions (p 225)NADP (p 227)photolysis (p 227)photosynthesis (p 225)pigment (p 226)
PhotosynthesisTrapping theSunrsquos Energy
Getting Energyto Make ATP
STUDY GUIDESTUDY GUIDE
CHAPTER 9 ASSESSMENT 241
To help you review photo-synthesis and cellular respiration use theOrganizational Study Fold on page 225
(t)Tom McHughPhoto Researchers (b)Matt Meadows
The Need forEnergy
Section 92
Section 93 Vocabularyaerobic (p 231)alcoholic fermentation
(p 236)anaerobic (p 231)cellular respiration
(p 231)citric acid cycle (p 232)glycolysis (p 231)lactic acid fermentation
(p 236)
Key Concepts ATP is the molecule that stores energy for
easy use within the cell ATP is formed when a phosphate group is
added to ADP When ATP is brokendown ADP and phosphate are formed andenergy is released
Green organisms trap the energy in sun-light and store it in the bonds of certainmolecules for later use
Organisms that cannot use sunlight directlyobtain energy by consuming plants or otherorganisms that have consumed plants
Key Concepts Photosynthesis is the process by which cells
use light energy to make simple sugars Chlorophyll in the chloroplasts of plant
cells traps light energy needed for photosynthesis
The light reactions of photosynthesis pro-duce ATP and result in the splitting ofwater molecules
The reactions of the Calvin cycle makecarbohydrates using CO2 along with ATPand NADPH from the light reactions
Key Concepts In cellular respiration cells break down
carbohydrates to release energy The first stage of cellular respiration gly-
colysis takes place in the cytoplasm anddoes not require oxygen
The citric acid cycle takes place in mito-chondria and requires oxygen
ncbdolglencoecomvocabulary_puzzlemaker
0231-0243 C9S3 BDOL-829900 8404 511 AM Page 241
242 CHAPTER 9 ASSESSMENT
Review the Chapter 9 vocabulary words listed inthe Study Guide on page 241 For each set ofvocabulary words choose the one that does notbelong Explain why it does not belong
1 light-dependent reactionsmdashCalvin cyclemdashchlorophyll
2 glycolysismdashalcoholic fermentationmdashaerobic3 NADPmdashchlorophyllmdashpigment4 photolysismdashCalvin cyclemdashlight-dependent
reactions5 cellular respirationmdashcitric acid cyclemdash
photosynthesis
6 Which of the following is a product of theCalvin cycleA carbon dioxideB NADP
C oxygenD FADH2
7 ________ processes require oxygen whereas________ processes do notA AnaerobicmdashaerobicB AerobicmdashanaerobicC PhotolysismdashaerobicD Aerobicmdashrespiration
8 Four molecules of glucose would give a netyield of ________ ATP following glycolysisA 8 C 4B 16 D 12
9 In which of the following structures do thelight-independent reactions of photosynthesistake placeA C
B D
10 What is the first process in an animal cell tobe affected by anaerobic conditionsA citric acid cycleB fermentationC glycolysisD electron transport chain
11 In which stage of cellular respiration is glucose broken down into two molecules of pyruvic acidA Calvin cycleB glycolysisC citric acid cycle D electron transport chain
12 Which of the following is a similarity betweenthe citric acid cycle and the Calvin cycleA Both cycles utilize oxygenB Both cycles produce carbon dioxideC Both cycles utilize ATP to break down
carbon bondsD Both cycles recycle the molecule needed
for the first reaction13 When yeast ferments the sugar in a bread
mixture what is produced that causes thebread dough to riseA carbon dioxide C ethyl alcoholB water D oxygen
14 Open Ended Why would human musclecells contain many more mitochondria thanskin cells
15 Open Ended How are cellular respirationand photosynthesis complementaryprocesses
16 Open Ended What happens to sunlight that strikes a leaf but is not trapped bychlorophyll
17 Sequence Describe the pathway of elec-trons from the time they enter the inter-membrane space of the mitochondrion tothe time they are returned to the inside ofthe mitochondrion
ncbdolglencoecomchapter_test
0231-0243 C9S3 BDOL-829900 8404 512 AM Page 242
CHAPTER 9 ASSESSMENT 243
18 Concept Map Make a concept map usingthe following vocabulary terms cellular res-piration glycolysis citric acid cycle electrontransport chain
19 Muscle tissueis made of different types of fibersmdashfast-twitchand slow-twitch These fibers vary in meta-bolic activities Visit to find out about the various types of musclefibers How do the metabolic activities ofthese fibers vary What types of fibers areused for different movements and why
REAL WORLD BIOCHALLENGE
are the steps of
2
4
1 3
which takes place in mitochondria
Multiple ChoiceStudy the table and answer questions20ndash23
The following experimental data wascollected by placing equal amounts ofvarious plant parts in sealed containersand exposing them to various light col-ors After eight hours in the containerthe increase in oxygen was measured in the container
Rate of PhotosynthesisContainer Plant Plant Part Light Color Temperature Increase
(degC) in O2 (mL)
1 Geranium Leaf Red 22 120
2 Geranium Leaf Green 22 15
3 Geranium Root Red 22 0
4 Violet Leaf Red 22 80
5 Violet Leaf Green 22 10
ncbdolglencoecom
20 One could compare the amount of oxygenproduced in eight hours at two differentlight colors by comparing _________A 1 and 3 C 1 and 5B 2 and 4 D 1 and 2
21 In which container was photosynthesis tak-ing place at the fastest rateA 1 C 3B 2 D 4
22 In which container was photosynthesis notoccurringA 1 C 3B 2 D 4
23 According to the data which variable determined whether or not photosynthesisoccurredA plant C temperatureB light color D plant part
Constructed ResponseGrid InRecord your answers on your answer document
24 Open Ended Compare the energy storage in photosynthesis to the energy storage in cellular respiration
25 Open Ended Compare alcoholic fermentation and lactic acid fermentation in terms of startingand ending material and ATP production
The assessed North Carolina objective appears next to the question
205
205
205
102
205
205
ncbdolglencoecomstandardized_test
0231-0243 C9S3 BDOL-829900 8404 513 AM Page 243
The Chemistry of LifeAlthough you are studying biology chemistry is
fundamental to all biological functions Under-standing some of the basic concepts of chemistrywill enhance your understanding of the biologicalworld
Elements and AtomsEvery substance in and on Earth is composed
of one or more kinds of elements An atom thesmallest component of an element is made ofeven smaller particles called electrons protonsand neutrons Atoms react to form compounds
The Life of a CellAll organisms are made of cells and each cell
is like a complex self-contained machine thatcan perform life functions Yet as small as they areall of the mechanisms and processes of these littlemachines are not fully known and scientistscontinue to unravel the marvelous mysteries of the living cell
The Cell Theory
Van Leeuwenhoek might haveviewed microorganisms likethese found in a droplet ofpond water
LM Magnification 100
Carbon IsotopesIsotopes of carbon contain different numbersof neutronsCarbon-12 six protons and six neutronsCarbon-13 six protons and seven neutronsCarbon-14 six protons and eight neutrons
Cells are microscopic machines
244
In the 1600s Anton van Leeuwenhoek was the first personto view living organisms through a microscope Another sci-
entist Robert Hooke named the structures cells Two hundredyears later several scientists including Matthias SchleidenTheodor Schwann and Rudolf Virchow continued to studyanimal and plant tissues under the microscope Conclusionsfrom many scientists were combined to form the cell theory
1 All organisms are composed of one or more cells2 The cell is the basic unit of organization of organisms3 All cells come from preexisting cells
(t)Michael RosenfelfTony Stone Images (b)Science VUVisuals Unlimited
0244-0249 U3 BDRev BDOL-829900 8404 144 PM Page 244
r-phosphate bone
rogen bonds betweengenous bases
A
A
A
P
P
P
P
D
D
D
D
D
D
D
DT
T
T
G
G
C
C
Substrate
Activesite
The Life of a Cell
Color-enhanced TEM Magnification 41 150
An enzyme has an area called anactive site in which a specific sub-strate undergoes a chemical reaction
Color-enhanced TEMMagnification 4800
Nucleic acids are made of subunits called nucleo-tides Each one consists of a sugar a phosphate groupand a nitrogenous base
Organelles
THE LIFE OF A CELL 245
A prokaryotic cell does notcontain membrane-boundorganelles
Organic CompoundsCarbohydrates are chemical compounds made
of carbon hydrogen and oxygen Common carbo-hydrates include sugars starches and celluloseLipids known as fats and oils contain a glycerolbackbone and three fatty acid chains Proteins arelarge molecules made of amino acids connected bypeptide bonds Enzymes are proteins that changethe rates of chemical reactions Nucleic acids suchas DNA and RNA are complex biomolecules thatstore cellular information in the form of a code
Eukaryotes and Prokaryotes All cells are surrounded by a plasma membrane
Eukaryotic cells contain membrane-bound organelleswithin the cell Cells without internal membrane-bound organelles are called prokaryotic cells
A eukaryotic cell con-tains membrane-bound organelles
(t)Dr Kari LounatmaaScience Photo LibraryPhoto Researchers (b)Moredun Animal Health LtdScience Photo LibraryPhoto Researchers
0244-0249 U3 BDRev BDOL-829900 8404 145 PM Page 245
246 BIODIGEST UNIT 3 REVIEW
Carbohydrate
Phospholipidbilayer
ProteinFatty acid tail
Phosphate head
The plasma membrane is composed ofa lipid bilayer with embedded proteins
Plasma membrane
Mitochondrion
Nucleus
Chloroplast
Cell wall
Vacuole
Golgi apparatus
Ribosomes
Roughendoplasmic
reticulum
Plant cell Animal cell
The Life of a Cell
Color-enhanced TEM Magnification unavailable Color-enhanced TEM Magnification 1250
Cell Organelles The organelles of a cell work together to carry
out the functions necessary for cell survival
Gateway to the CellAccording to the fluid mosaic model the
plasma membrane is formed by two layers ofphospholipids with the fatty acid chains facingeach other the phosphate groups face the cellrsquosinternal and external environments and proteinsare embedded in the membrane
Control of Cell FunctionsThe nucleus contains the master plans for pro-
teins which are then produced by organellescalled ribosomes The nucleus also controls cellularfunctions
Assembly Transport and Storage The cytoplasm suspends the cellrsquos organelles
including endoplasmic reticulum Golgi apparatusvacuoles and lysosomes The endoplasmic reticulumand Golgi apparatus transport and modify proteins
Energy Transformers Chloroplasts are found in plant cells They
capture the sunrsquos light energy so it can be trans-formed into useable chemical energy Mitochon-dria are found in both animal and plant cells They transform the food you eat into a useableenergy form
Support and LocomotionA network of microfilaments and microtubules
attach to the plasma membrane to give the cellstructure Cilia are short numerous projections thatmove like the oars of a boat Flagella are longerprojections that move in a whiplike fashion to propel a cell
(l)Biophoto AssociatesPhoto Researchers (r) Dr Gopel MurtiPhototake NYC
0244-0249 U3 BDRev BDOL-829900 8404 146 PM Page 246
The Life of a Cell
Cellular EnvironmentsIsotonic solution same number of dissolvedsubstances inside and outside the cellHypotonic solution more dissolved sub-stances inside the cell water enters the cellHypertonic solution fewer dissolved sub-stances inside the cell water leaves the cell
ATP production for eachmolecule of glucoseGlycolysis produces a net gain of two ATPtwo NADH and two H+
Citric acid cycle (Krebs cycle) producestwo ATP six NADH and two FADH2Electron transport chain produces 32 ATPfrom NADH and FADH2Lactic acid fermentation produces two ATPand lactic acid
THE LIFE OF A CELL 247
Interphase
Prophase
Metaphase
Anaphase
Telophase
During the stages of mitosis chromosomes are sepa-rated into two daughter cells
Carrier protein
Higher concentrationof ions
Ions Lower concentrationof ions Energy
Active transport
Diffusion and OsmosisThe selectively permeable plasma membrane
allows only certain substances to cross Diffusion is the movement of a substance from an area ofhigher concentration to an area of lower concen-tration Diffusion of water across a selectively per-meable membrane is called osmosis
Simple diffusion occurs by random movementof molecules or ions In facilitated diffusion pro-teins bind to and move molecules across a mem-brane Active transport uses energy to movemolecules against a concentration gradient
Energy in a Cell Adenosine triphosphate (ATP) is the most com-
mon energy source in a cell Two organelles helpform ATP from other sources of energy
Chloroplasts in plant cells convert energy fromthe sunrsquos rays into ATP using light-dependent reac-tions and store that energy in sugars via light-independent reactions and the Calvin cycle
Mitochondria in both plant and animal cells con-vert food energy into ATP through a series ofchemical reactions including glycolysis the citricacid cycle and the electron transport chain
MitosisAs cells grow they reach a size where the
plasma membrane cannot transport enough nutri-ents and wastes to maintain cell growth At thispoint the cell undergoes mitosis and divides
The period prior to mitosis called interphase isone of intense metabolic activity The first stage ofmitosis is prophase when the duplicated chromo-somes condense and the mitotic spindle forms Thechromosomes line up in the center of the cell dur-ing metaphase and slowly separate during ana-phase In telophase the nucleus divides followedby cytokinesis which separates the daughter cells
0244-0249 U3 BDRev BDOL-829900 8404 147 PM Page 247
248 UNIT 3 STANDARDIZED TEST PRACTICE
Chromosome Comparison of Four Organisms
Organism Human Rye Potato Guinea pig
Number of chromosomes 46 14 48 64in body cells
Number of chromatids 92 A 96 128during metaphase
Number of chromosomes 46 14 48 64in daughter cells
Multiple Choice
Use the table below to answer questions 1ndash3
1 What number belongs in the space labeled Aunder ldquoRyerdquo in the tableA 14 C 7B 28 D 21
2 If one pair of chromatids failed to separateduring mitosis in rye cells how many chromo-somes would end up in the two daughter cellsA 28 and 28B 14 and 14C 7 and 8D 13 and 15
3 What is the relationship between the numberof chromosomes in body cells and the com-plexity of an organismA The more complex the organism the more
chromosomes it hasB The more complex the organism the fewer
chromosomes it hasC There is no relationshipD The number of chromosomes is deter-
mined by the sex of the organism
4 The isotopes of the element magnesium differin their number of ________A proteinsB electronsC neutronsD protons
5 Which of the following organelles are found inall cellsA plasma membrane and ribosomesB mitochondria and chloroplastsC microtubules and lysosomesD Golgi apparatus and endoplasmic reticulum
6 During late interphase the chromosomes dou-ble to form chromatids that are attached toeach other During which phase of mitosis dothe chromatids separateA prophaseB metaphaseC anaphaseD telophase
7 Plants must have a constant supply of ________for photosynthesis but they provide ________for cellular respirationA watermdashcarbon dioxideB carbon dioxidemdashwaterC carbon dioxidemdashoxygenD oxygenmdashwater
8 Which type of bond involves the sharing of electronsA covalentB ionicC hydrogenD electrostatic
9 The primary organelle used for storing infor-mation in a cell is the ________A cell wallB endoplasmic reticulumC mitochondriaD nucleus
When EliminatingCross It Out
List the answer choice letters on scratch paperand with your pencil cross out choices yoursquoveeliminated Yoursquoll stop yourself from choosingan answer yoursquove mentally eliminated
The assessed North Carolina objective appears next to the questionEnd-of-Course Test Practice
202
205
202
0244-0249 U3 BDRev BDOL-829900 8404 541 PM Page 248
UNIT 3 STANDARDIZED TEST PRACTICE 249
10 A biologist studies cells under a microscopethat have been drawn from an unknown solu-tion The cells appear shriveled What can thebiologist conclude about the solution A It is hypotonicB It is isotonicC It is hypertonicD It is polar
11 Which helps capture the sunrsquos energyA light-dependent reactionsB citric acid cycleC Calvin cycleD light-independent reactions
Use the word equation below to answer questions12ndash14
sucrose water glucose fructose
12 The reaction above illustrates the ________A hydrolysis of sucroseB condensation of sucroseC hydrolysis of glucoseD condensation of fructose
13 The product(s) of this reaction isare________A sucroseB waterC glucose and fructoseD sucrose and water
14 Glucose and fructose are ________A disaccharidesB polysaccharidesC monosaccharidesD starches
Use the figure below to answer questions 15ndash17
15 The illustrations above demonstrate the trans-port of an ion across the plasma membranebut they are out of sequence In what order dothey belongA D-C-B-A C C-B-D-AB A-B-D-C D A-D-B-C
16 What statement is true about diagram DA The ion movement is randomB Energy is requiredC The fatty acids in the plasma membrane
could also move apart to allow the ionthrough
D The concentration of ions is higher at thetop of diagram D than at the bottom
17 Which process is best represented by these diagramsA diffusion C endocytosisB active transport D passive transport
Energy
A B
C D
Constructed ResponseGrid In
Record your answers on your answer document
18 Open Ended How is an ionic bond different from a covalent bond
19 Open Ended Describe the role of transport proteins in plasma membranes
20 Open Ended Compare the functions of mitochondria and chloroplasts in cells Be sure to includeATP in your answer
21 Open Ended Describe the cellular process of mitosis
205
203
202
203
203
203
ncbdolglencoecomstandardized_test
0244-0249 U3 BDRev BDOL-829900 8404 542 PM Page 249
- Biology The Dynamics of LifemdashNorth Carolina Edition
-
- Contents in Brief
-
- The North Carolina Biology Handbook
-
- Correlations to the North Carolina Objectives
-
- North Carolina Objectives to Biology The Dynamics of Life
- Biology The Dynamics of Life to North Carolina Objectives
-
- How to Master the North Carolina Objectives
- End-of-Course Test Practice Countdown
-
- Table of Contents
-
- Unit 1 What is biology
-
- Chapter 1 Biology The Study of Life
-
- Section 11 What is biology
-
- MiniLab 11 Predicting Whether Mildew Is Alive
- Careers in Biology Nature Preserve Interpreter
-
- Section 12 The Methods of Biology
-
- MiniLab 12 Testing for Alcohol
- Problem-Solving Lab 11
- Inside Story Scientific Methods
-
- Section 13 The Nature of Biology
-
- Problem-Solving Lab 12
- MiniLab 13 Hatching Dinosaurs
- Internet BioLab Collecting Biological Data
- Biology and Society Organic Food Is it healthier
-
- Chapter 1 Assessment
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- BioDigest What is biology
- Unit 1 Standardized Test Practice
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- Unit 2 Ecology
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- Chapter 2 Principles of Ecology
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- Section 21 Organisms and Their Environment
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- MiniLab 21 Salt Tolerance of Seeds
- Problem-Solving Lab 21
- Careers in Biology Science Reporter
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- Section 22 Nutrition and Energy Flow
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- Problem-Solving Lab 22
- Physical Science Connection Conservation of Energy
- Physical Science Connection Conservation of Mass
- MiniLab 22 Detecting Carbon Dioxide
- Inside Story The Carbon Cycle
- Design Your Own BioLab How can one population affect another
- Biology and Society The EvergladesmdashRestoring an Ecosystem
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- Chapter 2 Assessment
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- Chapter 3 Communities and Biomes
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- Section 31 Communities
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- MiniLab 31 Looking at Lichens
- Problem-Solving Lab 31
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- Section 32 Biomes
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- Physical Science Connection Salinity and Density of a Solution
- Problem-Solving Lab 32
- MiniLab 32 Marine Plankton
- Inside Story A Tropical Rain Forest
- Investigate BioLab Succession in a Jar
- Connection to Literature Our National Parks by John Muir
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- Chapter 3 Assessment
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- Chapter 4 Population Biology
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- Section 41 Population Dynamics
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- MiniLab 41 Fruit Fly Population Growth
- Inside Story Population Growth
- Problem-Solving Lab 41
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- Section 42 Human Population
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- Problem-Solving Lab 42
- MiniLab 42 Doubling Time
- Investigate BioLab How can you determine the size of an animal population
- Connection to Chemistry Polymers for People
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- Chapter 4 Assessment
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- Chapter 5 Biological Diversity and Conservation
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- Section 51 Vanishing Species
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- MiniLab 51 Field Investigation
- Problem-Solving Lab 51
- Physical Science Connection Environmental Impact of Generating Electricity
- Physical Science Connection Wave Energy
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- Section 52 Conservation of Biodiversity
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- MiniLab 52 Conservation of Soil
- Problem-Solving Lab 52
- Internet BioLab Researching Information on Exotic Pets
- Connection to Art Photographing Life
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- Chapter 5 Assessment
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- BioDigest Ecology
- Unit 2 Standardized Test Practice
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- Unit 3 The Life of a Cell
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- Chapter 6 The Chemistry of Life
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- Section 61 Atoms and Their Interactions
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- Problem-Solving Lab 61
- Physical Science Connection Chemical Bonding and the Periodic Table
- Physical Science Connection Conservation of Mass in Chemical Reactions
- Careers in Biology WeedPest Control Technician
- MiniLab 61 Determine pH
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- Section 62 Water and Diffusion
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- Physical Science Connection The Structure of Water Molecules
- Physical Science Connection Density of Liquids
- Problem-Solving Lab 62
- MiniLab 62 Investigate the Rate of Diffusion
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- Section 63 Life Substances
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- Inside Story Action of Enzymes
- Design Your Own BioLab Does temperature affect an enzyme reaction
- BioTechnology The Good News and the Bad News About Cholesterol
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- Chapter 6 Assessment
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- Chapter 7 A View of the Cell
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- Section 71 The Discovery of Cells
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- Physical Science Connection Lenses and the Refraction of Light
- MiniLab 71 Measuring Objects Under a Microscope
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- Section 72 The Plasma Membrane
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- Problem-Solving Lab 71
- Physical Science Connection Solubility and the Nature of Solute and Solvent
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- Section 73 Eukaryotic Cell Structure
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- Problem-Solving Lab 72
- MiniLab 72 Cell Organelles
- Physical Science Connection Conservation of Energy
- Inside Story Comparing Animal and Plant Cells
- Investigate BioLab Observing and Comparing Different Cell Types
- Connection to Literature The Lives of a Cell by Lewis Thomas
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- Chapter 7 Assessment
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- Chapter 8 Cellular Transport and the Cell Cycle
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- Section 81 Cellular Transport
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- MiniLab 81 Cell Membrane Simulation
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- Section 82 Cell Growth and Reproduction
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- Problem-Solving Lab 81
- Problem-Solving Lab 82
- Inside Story Chromosome Structure
- MiniLab 82 Seeing Asters
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- Section 83 Control of the Cell Cycle
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- Problem-Solving Lab 83
- Investigate BioLab Where is mitosis most common
- Connection to Health Skin Cancer
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- Chapter 8 Assessment
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- Chapter 9 Energy in a Cell
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- Section 91 The Need for Energy
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- Problem-Solving Lab 91
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- Section 92 Photosynthesis Trapping the Suns Energy
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- MiniLab 91 Separating Pigments
- MiniLab 92 Use Isotopes to Understand Photosynthesis
- Inside Story The Calvin Cycle
- Biotechnology Careers Biochemist
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- Section 93 Getting Energy to Make ATP
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- Inside Story The Citric Acid Cycle
- Problem-Solving Lab 92
- MiniLab 93 Determine if Apple Juice Ferments
- Internet BioLab What factors influence photosynthesis
- Connection to Chemistry Plant Pigments
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- Chapter 9 Assessment
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- BioDigest The Life of a Cell
- Unit 3 Standardized Test Practice
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- Unit 4 Genetics
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- Chapter 10 Mendel and Meiosis
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- Section 101 Mendels Laws of Heredity
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- MiniLab 101 Looking at Pollen
- Problem-Solving Lab 101
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- Section 102 Meiosis
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- Problem-Solving Lab 102
- MiniLab 102 Modeling Crossing Over
- Inside Story Chromosome Mapping
- Internet BioLab How can phenotypes and genotypes of plants be determined
- Connection to Math A Solution from Ratios
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- Chapter 10 Assessment
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- Chapter 11 DNA and Genes
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- Section 111 DNA The Molecule of Heredity
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- Problem-Solving Lab 111
- Inside Story Copying DNA
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- Section 112 From DNA to Protein
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- Problem-Solving Lab 112
- MiniLab 111 Transcribe and Translate
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- Section 113 Genetic Changes
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- Physical Science Connection Gamma Radiation as a Wave
- Careers in Biology Genetic Counselor
- Problem-Solving Lab 113
- MiniLab 112 Gene Mutations and Proteins
- Investigate BioLab RNA Transcription
- BioTechnology Scanning Probe Microscopes
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- Chapter 11 Assessment
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- Chapter 12 Patterns of Heredity and Human Genetics
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- Section 121 Mendelian Inheritance of Human Traits
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- MiniLab 121 Illustrating a Pedigree
- Problem-Solving Lab 121
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- Section 122 When Heredity Follows Different Rules
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- Problem-Solving Lab 122
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- Section 123 Complex Inheritance of Human Traits
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- Inside Story The ABO Blood Group
- Problem-Solving Lab 123
- MiniLab 122 Detecting Colors and Patterns in Eyes
- Design Your Own BioLab What is the pattern of cytoplasmic inheritance
- Connection to Social Studies Queen Victoria and Royal Hemophilia
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- Chapter 12 Assessment
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- Chapter 13 Genetic Technology
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- Section 131 Applied Genetics
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- Problem-Solving Lab 131
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- Section 132 Recombinant DNA Technology
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- MiniLab 131 Matching Restriction Enzymes to Cleavage Sites
- Inside Story Gel Electrophoresis
- Problem-Solving Lab 132
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- Section 133 The Human Genome
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- MiniLab 132 Storing the Human Genome
- Biotechnology Careers Forensic Analyst
- Problem-Solving Lab 133
- Investigate BioLab Modeling Recombinant DNA
- BioTechnology New Vaccines
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- Chapter 13 Assessment
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