Fall Semester Review

AP/IB Biology

The Discovery of Plant Hormones

• Any growth response– That results in curvatures of whole plant organs

toward or away from a stimulus is called a tropism– Is often caused by hormones

Auxin– Is used for any chemical substance that promotes

cell elongation in different target tissues

• Auxin transporters– Move the hormone out of

the basal end of one cell, and into the apical end of neighboring cells

• Auxin– Is involved in the formation and branching of roots

Other Effects of Auxin

• Auxin affects secondary growth– By inducing cell division in the vascular cambium

and influencing differentiation of secondary xylem

• Developing seeds synthesize auxin• tomatoes grown in greenhouse conditions sprayed with auxin

induce fruit development without a need for pollination• This allows for seedless tomatoes

• Charles Darwin and his son Francis– Conducted some of the earliest experiments on phototropism, a plant’s

response to light, in the late 19th century

In 1880, Charles Darwin and his son Francis designed an experiment to determine what part of the coleoptile senses light. In 1913, Peter Boysen-Jensen conducted an experiment to determine how the signal for phototropism is transmitted.

EXPERIMENT

In the Darwins’ experiment, a phototropic response occurred only when light could reach the tip of coleoptile. Therefore, they concluded that only the tip senses light. Boysen-Jensen observed that a phototropic response occurred if the tip was separated by a permeable barrier (gelatin)but not if separated by an impermeable solid barrier (a mineral called mica). These results suggested that the signal is a light-activated mobile chemical.

CONCLUSION

RESULTS

Control Darwin and Darwin (1880) Boysen-Jensen (1913)

Light

Shadedside ofcoleoptile

Illuminatedside ofcoleoptile

Light

Tipremoved

Tip coveredby opaquecap

Tipcoveredby trans-parentcap

Base coveredby opaqueshield

Light

Tip separatedby gelatinblock

Tip separatedby mica

• In 1926, Frits Went– Extracted the

chemical messenger for phototropism, auxin, by removing the coleoptile tip & placed it on a block of agar. This will allow the chemical to travel through. Went concluded that a coleoptile curved toward light because its dark

side had a higher concentration of the growth-promoting chemical, which he named auxin.

The coleoptile grew straight if the chemical was distributed evenly. If the chemical was distributed unevenly, the coleoptile curved away from the side with the block, as if growing toward light, even though it was grown in the dark.

Excised tip placedon agar block

Growth-promotingchemical diffusesinto agar block

Agar blockwith chemicalstimulates growth

Control(agar blocklackingchemical)has noeffectControl

Offset blockscause curvature

RESULTS

CONCLUSION

In 1926, Frits Went’s experiment identified how a growth-promoting chemical causes a coleoptile to grow toward light. He placed coleoptiles in the dark and removed their tips, putting some tips on agar blocks that he predicted would absorb the chemical. On a control coleoptile, he placed a block that lacked the chemical. On others,he placed blocks containing the chemical, either centered on top of the coleoptile to distribute the chemical evenly or offset to increase the concentration on one side.

EXPERIMENT

Photoperiodism

• plant's ability to flower in response to changes in the photoperiod: the relative lengths of day and night.

• research has shown that the dark period is more important than the light period. For example, if SDPs are grown under short-day conditions but the dark period is interrupted by a flash of light, the SDPs will not flower. The long night that normally accompanies a short day is interrupted by the flash. An interruption of the light period with dark has no effect.

Animal Behavior

Fixed Action Patterns (FAP)

• FAP is an instinctive behavioral response triggered by a very specific stimulus.

• Once triggered, the FAP behavior can’t be stopped ‘midstream’, but must play out to completion.

Egg Rolling and the Greylag Goose

If one of the gooses' egg rolls away from the nest, the goose automatically rolls the egg back to the nest with a repeated, specific action. When the female notices an egg outside the nest (sign stimulus), she begins this repeated movement to drag the egg with her beak and neck.

If, while the goose is rolling the egg back to the nest, the egg slides off to the side, or is removed by an observer, the goose continues to repeat the stereotypic movements, until she reaches the nest. She'll then relocate the missing egg and begin the process all over again.

GREYLAG GOOSE SHOW VIDEO

Innate Behavior

HabituationAn organism decreases or ceases to respond to a stimulus after repeated presentations.

Operant Conditioninga method of learning that occurs through rewards and punishments for behavior. Through operant conditioning, an association is made between a behavior and a consequence for that behavior.

Classical ConditioningA learning process that occurs through associations between an environmental stimulus and a naturally occurring stimulus.

It's important to note that classical conditioning involves placing a neutral signal (bell) before a naturally occurring reflex (salivating in response to food).

Classical conditioning basically involves forming an association between two stimuli resulting in a learned response.

Taxis and KinesisTaxis has a specific and directed motion while kinesis has a random and undirected motion.

Woodlice prefer moist areas so they will move around less than in dry areas. In dry areas they will move around a lot (randomly) until they hit upon a moist area

Magnification and scales

2. In Figure 12 the actual length of the mitochondrion is 8µm. (a) Determine the magnification of this electron micrograph. (b) Calculate how long a 5 µm scale bar would be on this electron micrograph. (c) Determine the width of the mitochondrion.

a) Magnification = image size = 63mm 63000µm = 7875x ~ 8000x actual size 8µm 8µm

b) 8000 = X__ 8000 x 5 = 40,000µm = 40mm 5µm

c) Depending on your measurement location the image width is b/w 20mm & 23mm. We will use 20mm. magnification (8000) = 20,000 µm = 20,000 / 80000 = 2.5µm X

Magnification = size of image actual size of specimen

Ionic and Covalent Bonds

Ionic Bonding

• A strong bond• Opposite charge atoms bond & an electron is lost

by one atom & gained by the other.– Cation: when the charge of an atom is positive

• The atom lost an electron– Anion: when the charge of the atom is negative

• The atom gained an electron

Ionic Bonds

The formation of the ionic bond in table salt

NaCl Crystal

Everyday tablesalt

Covalent Bonding

VERY STRONG BOND

pH

• A convenient way to express the hydrogen ion concentration of a solution

pH

pH = log [H+]_

The pH scale is logarithmicA difference of one unit represents a ten-fold change in H+ concentration

AcidDissociates in water to increase H+ concentration

BaseCombines with H+ when dissolved in water

• Hydrogen ion reservoirs that take up or release H+ as needed

• The key buffer in blood is an acid-base pair (carbonic acid-bicarbonate buffering system)

Buffers

Response to a drop in pH

H2OWater in

blood plasma

CO2

Carbon dioxide

+

H2CO3

Carbonic acid

++

–

HCO3–

Bicarbonateion

H+

Hydrogenion

Response to a rise in pH

Importance of Water

Hydrogen Bonds Give Water Unique Properties

• Water molecules are polar molecules• Unequal sharing of electrons & V-like shape– They can thus form hydrogen bonds with each other

and with other polar molecules

• Each hydrogen bond is very weak– However, the cumulative effect of enormous numbers

can make them quite strong

• Hydrogen bonding is responsible for many of the physical properties of water

COHESIVE PROPERTIES

THERMAL PROPERTIES

High Specific HeatWater can absorb or release a lot of heat without changing its own temperature by very much.

High Heat of VaporizationWater absorbs a lot of heat,

hydrogen bonds break, then water turns to vapor & then evaporates.

WATER AS ICE, FLOATS

Liquid water

Ice

SOLVENT PROPERTIES

Water is a versatile solvent because of its polarity

Most of the important molecules in and out of the cell are polar molecules. These molecules create solutions that enable for biochemical processes to occur.

Gas Exchange

Protein synthesis & glycolysis

Light independent processes of photosynthesisWater forms a hydration shell around each solute ion.

Salt dissolves when all ions have separated

from the crystal

Functional Groups and Macromolecules

WHAT IS THE DIFFERENCE BETWEEN A MONOMER & A POLYMER?

SYNTHESIS AND BREAKDOWN OF POLYMERS

Enzymes help

Dehydration (Condensation) reactionTo connect monomers togetherA water molecule is released

One molecule gives up a hydroxyl group & the other a hydrogen

HydrolysisPolymers are broken apart to monomers

A water molecule is added to split apart the monomers

EX: Digestion

VARIOUS MONOSACCHARIDES

What do all of these sugars have in

common?

They are made of one carbonyl group

and several hydroxyl groups.

What’s the difference between the top row of sugars compared to the bottom row?

The top sugars have their carbonyl group at the end of the carbon skeleton &

the bottom ones have their carbonyl group in the

middle Identify the difference between glucose & galactose.

Lipids• Large nonpolar molecules that are insoluble in

water• They are NOT polymers but they are large

molecules assembled from smaller molecules.

• Three major types– Triglycerides– Phospholipids– Steroids

• A modified fat – One of the three fatty acids is replaced by a

phosphate and a small polar functional group

Phospholipids

Essential to cells: they make up the cell membrane.

Nucleic Acids• Serve as information storage molecules

• Store, transmit and help express hereditary information

• Long polymers of repeating subunits termed nucleotides

• A nucleotide is composed of three parts– Five-carbon sugar– Nitrogen-containing base– Phosphate

• Primary structure– The specific amino acid sequence of a protein

• Secondary structure– The initial folding of the amino acid chain by hydrogen

bonding• Tertiary structure

– The final three-dimensional shape of the protein• Quaternary structure

– The spatial arrangement of polypeptides in a multi-component protein

Protein Structure

Enzymes• Influence the rate of reaction• A set of reactants present with enzymes will

form products at a faster rate than without enzymes.

• Enzymes cannot force reactions to occur that would not normally occur

• The enzymes role is to lower the energy level needed to start the reaction.– Enzymes lower the activation energy of reactions

• Enzymes are not used up during the reaction

Prokaryotic and Eukaryotic Cells

PROKARYOTIC

• Smaller & simpler• Less than 10µm in diameter• DNA in ring form without

protein• DNA is free floating• No mitochondria• 70S ribosomes• No internal

compartmentalization to form organelles

• Thought to be the 1st cells on Earth.

• Reproduce by Binary Fission• EX: BACTERIA

• EUKARYOTIC

• Bigger & more complex• More than 10µm• DNA with proteins as

chromosomes/chromatin• DNA enclosed in nucleus• Mitochondria is present• 80S ribosomes• Internal compartmentalization

present to form many types of organelles.

• EX: EVERYTHING EXCEPT BACTERIA

Variations among Eukaryotic Cells

• Plant cells• Exterior of cell includes cell

wall• Have chloroplasts• Possess large vacuole that’s

centrally located• Store carbohydrates as

starch• Do not contain centrioles• Has a fixed often angular

shape

• Animal cells• Exterior of cell includes

plasma membrane• No chloroplasts• Vacuoles are usually not

present or are very small• Store carbohydrates as

glycogen• Have centrioles• Is flexible and more likely to

be rounded in shape.

HOW ARE THE MITOCHONDRIA AND CHLOROPLASTS SIMILAR TO PROKARYOTIC

CELLS?

SIZE BOTH HAVE THEIR OWN DNA

THEY ARE NOT PART OF THE ENDOMEMBRANE SYSTEM

SOME PROTEINS NEEDED ARE MADE BY THEIR RIBOSOMES LOCATED IN THEIR MEMBRANE & OTHER PROTEINS ARE BROUGHT IN FROM THE CYTOSOL

THEY REPRODUCE IN A SEMIAUTONOMOUS

MANNER

Why do mitochondria & chloroplasts have so many membranes in them?

For increased surface area used for the energy conversion processes that occur in these

organelles.

Cellular Respiration

Oxidation and ReductionOxidation Reduction

Loss of electrons Gain of electrons

Gain of oxygen Loss of oxygen

Loss of hydrogen Gain of hydrogen

Results in many C – O bonds Results in many C – H bonds

Results in a compound with lower potential energy

Results in a compound with higher potential energy

A useful way to remember: OIL = Oxidation Is Loss (of electrons)

These two reactions occur together during chemical reactions= redox reactions. One compound’s or element’s loss is another compound’s or element’s gain.

RIG= Reduction Is Gain (of electrons)

Respiration

• Glycolysis– Breaks down glucose into two molecules of

pyruvate

• The citric acid cycle (Krebs Cycle)– Completes the breakdown of glucose

• Oxidative phosphorylation – Is driven by the electron transport chain– Generates ATP

Glycolysis• Harvests energy by oxidizing

glucose to pyruvate

• Glycolysis– Means “splitting of sugar”– Breaks down glucose into

pyruvate– Occurs in the cytoplasm of

the cell

• Two major phases– Energy investment phase– Energy payoff phase

Glycolysis Citricacidcycle

Oxidativephosphorylation

ATP ATP ATP

2 ATP

4 ATP

used

formed

Glucose

2 ATP + 2 P

4 ADP + 4 P

2 NAD+ + 4 e- + 4 H + 2 NADH + 2 H+

2 Pyruvate + 2 H2O

Energy investment phase

Energy payoff phase

Glucose 2 Pyruvate + 2 H2O4 ATP formed – 2 ATP

used 2 ATP

2 NAD+ + 4 e– + 4 H +

2 NADH

+ 2 H+

Figure 9.8

Glycolysis Summary

At the end you get these

–Pyruvate must first be converted to acetyl CoA, which links the cycle to glycolysis

Before the Krebs cycle can begin….we have the

link reactionCYTOSOL MITOCHONDRION

NADH + H+NAD+

2

31

CO2 Coenzyme APyruvate

Acetyle CoA

S CoA

C

CH3

O

Transport protein

O–

O

O

C

C

CH3

Figure 9.10

The Krebs Cycle

• 6 NADH's are generated • 2 FADH2 is generated • 2 ATP are generated • 4 CO2's are released

Two turns for each molecule of glucose because each glucose is converted to 2 molecules of acetyl CoA.

–Electron transfer causes protein complexes to pump H+ from the mitochondrial matrix to the intermembrane space

•The resulting H+ gradient

–Stores energy

–Drives chemiosmosis in ATP synthase

– Is referred to as a proton-motive force

ETC

How does electronegativity play a part in the electron transport chain?

Because each electron acceptor in the chain is more electronegative than the previous, the electron will move from one electron transport chain molecule to the next, falling closer and closer to the nucleus of the last electron acceptor.

Where do the electrons for the ETC come from?NADH and FADH2 which got theirs from glucose.

What molecule is the final acceptor of the electron?

Oxygen, from splitting O2 molecule & grabbing 2 H+ .

What’s consumed during this process?

O2

What’s gained by this process?

H+ inside the inner membrane space

• FADH2 enters the ETC at a lower free energy level than the NADH.– Results in FADH2 produces 2

ATP’s to NADH’s 3• Oxygen is the final electron

acceptor– The electrons + oxygen + 2

hydrogen ions = H2O

• Important to note that low amounts of energy is lost at each exchange along the ETC.

Chemiosmosis: The Energy-Coupling Mechanism

•ATP synthase

– Is the enzyme that actually makes ATP

INTERMEMBRANE SPACE

H+

H+

H+

H+

H+

H+ H+

H+

P i

+ADP

ATP

A rotor within the membrane spins clockwise whenH+ flows past it down the H+

gradient.

A stator anchoredin the membraneholds the knobstationary.

A rod (for “stalk”)extending into the knob alsospins, activatingcatalytic sites inthe knob.

Three catalytic sites in the stationary knobjoin inorganic Phosphate to ADPto make ATP. MITOCHONDRIAL MATRIXFigure 9.14

32-34 ATP

Oxidativephosphorylation.electron transportand chemiosmosis

Glycolysis

ATP ATP ATP

InnerMitochondrialmembrane

H+

H+H+

H+

H+

ATPP i

Protein complexof electron carners

Cyt c

I

II

III

IV

(Carrying electronsfrom, food)

NADH+

FADH2

NAD+

FAD+ 2 H+ + 1/2 O2

H2O

ADP +

Electron transport chainElectron transport and pumping of protons (H+),

which create an H+ gradient across the membrane

ChemiosmosisATP synthesis powered by the flowOf H+ back across the membrane

ATPsynthase

Q

Oxidative phosphorylation

Intermembranespace

Innermitochondrialmembrane

Mitochondrialmatrix

Figure 9.15

If one ATP molecule holds 7.3kcal of potential energy, how much potential energy does 1 glucose molecule produce in cell respiration?

One molecule of glucose actually contains 686 kcal/mol of potential energy. Where does the remaining energy go when glucose is reduced?

What is the net efficiency of cell respiration if glucose contains 686kcal and only 277.4kcal are produced?

Is cellular respiration endergonic or exergonic?

exergonic

Is it a catabolic or anabolic process?

catabolic

At its maximum output, 38 x 7.3kcal = 277.4kcal

It’s lost as heat-which is why our bodies are warm right now.

277.4/ 686 x 100 = 40% energy recovered from aerobic respiration

OCCURS IN CYTOSOL

OCCURS IN MITOCHONDRIA

OCCURS IN CYTOSOL

•Fermentation enables some cells to produce ATP without the use of oxygen

•Glycolysis

–Can produce ATP with or without oxygen, in aerobic or anaerobic conditions

–Couples with fermentation to produce ATP

Anaerobic Respiration

•Fermentation consists of

–Glycolysis plus reactions that regenerate NAD+, which can be reused by glyocolysis

•Alcohol fermentation

–Pyruvate is converted to ethanol in two steps, one of which releases CO2

•Lactic acid fermentation

–Pyruvate is reduced directly to NADH to form lactate as a waste product

Anaerobic Respiration

Stage 2: If oxygen is absent- Fermentation

-Produces organic molecules, including alcohol and lactic acid, and it occurs in the absence of oxygen.

Cells not getting enough oxygen, excess pyruvate molecules are converted into lactic acid molecules, raising the pH in the cells.

Yeast uses alcoholic fermentation for ATP generation.

Cell Communication

• Animal and plant cells– Have cell junctions that directly connect the

cytoplasm of adjacent cells

Plasma membranes

Plasmodesmatabetween plant cells

Gap junctionsbetween animal cells

Figure 11.3 (a) Cell junctions. Both animals and plants have cell junctions that allow molecules to pass readily between adjacent cells without crossing plasma membranes.

(b) Cell-cell recognition. Two cells in an animal may communicate by interaction between molecules protruding from their surfaces.

• In local signaling, animal cells– May communicate via direct contact

–EX: immune system & embryonic development

Cell to Cell Communication (no distance; passing a note)

Cell to Cell Communication (short distance…on the board message)

Local regulator = neurotransmitters

Neurons

• In other cases, animal cells– Communicate using local regulators

(a) Paracrine signaling. A secreting cell acts on nearby target cells by discharging molecules of a local regulator (a growth factor, for example) into the extracellular fluid.

(b) Synaptic signaling. A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell.

Local regulator diffuses through extracellular fluid

Target cell

Secretoryvesicle

Electrical signalalong nerve celltriggers release ofneurotransmitter

Neurotransmitter diffuses across

synapse

Target cellis stimulated

Local signaling

Growth factors Neurotransmitters

Cell to Cell Communication (long distance; hit a lot of cells…advertisement in local paper)

Message gets sent to a lot of different cells. Some will act on it and some won’t.

The ones that do act may not all act in the same way.

• In long-distance signaling– Both plants and animals use hormones

Hormone travelsin bloodstreamto target cells

(c) Hormonal signaling. Specialized endocrine cells secrete hormones into body fluids, often the blood. Hormones may reach virtually all body cells.

Long-distance signaling

Bloodvessel

Targetcell

Endocrine cell

Hormonal signaling AKA: endocrine signaling

Plant hormones

• Sometimes travel through vessels but more often travel through the air as gas (ethylene).

Paracrine signaling

Synaptic signaling

Hormonal signaling

What are theses types of signals? Are they short/local or long distance? Are they specific or

general?

Short/local & general Short/local and specific

Long distance and general or specific

The Stages of Cell Signaling: A Preview• Earl W. Sutherland

– Established that epinephrine causes glycogen breakdown without passing through the membrane.

– Discovered how the hormone epinephrine acts on cells

•Sutherland suggested that cells receiving signals went through three processes

– Reception– Transduction– Response

Reception- target cells detection of a signaling molecule (ligand) that binds to a receptor protein, causing it to change shape

Transduction-several steps where each molecule brings about a change in the next molecule

Response occurs with the last molecule in the transduction pathway & triggers the cell’s response.

• Plants have cellular receptors– That they use to detect important changes in their

environment• For a stimulus to elicit a response

– Certain cells must have an appropriate receptor

• The potato’s response to light– Is an example of cell-signal processing

Figure 39.3

CELLWALL

CYTOPLASM

1 Reception 2 Transduction 3 Response

Receptor

Relay molecules

Activationof cellularresponses

Hormone orenvironmentalstimulus

Plasma membrane

• Signal molecules that are small or hydrophobic– And can readily cross the

plasma membrane use these receptors

Other Type of Intracellular Receptors• Intracellular receptors

– Are cytoplasmic or nuclear proteins

Like undercover cops hidden in a crowd

• Receptor tyrosine kinases (insulin uses these)

Signalmolecule

Signal-binding sitea

CYTOPLASM

Tyrosines

Signal moleculeHelix in the

Membrane

Tyr

TyrTyr

TyrTyr

TyrTyr

TyrTyr

TyrTyr

Tyr

Tyr

TyrTyr

TyrTyr

Tyr Tyr

TyrTyr

TyrTyr

Tyr

Tyr

TyrTyr

TyrTyr

Tyr

DimerReceptor tyrosinekinase proteins(inactive monomers)

PPP

PP

P Tyr

TyrTyr

TyrTyr

TyrP

PP

PP

PCellularresponse 1

Inactiverelay proteins

Activatedrelay proteins

Cellularresponse 2

Activated tyrosine-kinase regions(unphosphorylateddimer)

Fully activated receptortyrosine-kinase(phosphorylateddimer)

6 ATP 6 ADP

Figure 11.7

Can trigger more than 1 signal transduction pathway-coordinates many aspects of cell growth & reproduction

-abnormal tyrosine receptors (function w/o signal molecules) may contribute to some cancers.

Kinase is an enzyme that catalyzes the transfer of phosphate groups

Like a friend who brings together 2 people who otherwise don’t hang out (unless it’s with this friend); the 3 have a greater time whenever they are together.

Signal molecule

Activeproteinkinase

1

Activeproteinkinase

2

Activeproteinkinase

3

Inactiveprotein kinase

1

Inactiveprotein kinase

2

Inactiveprotein kinase

3

Inactiveprotein

Activeprotein

Cellularresponse

Receptor

P

P

P

ATPADP

ADP

ADP

ATP

ATP

PP

PP

PP

Activated relaymolecule

i

Phosphorylation cascade

P

P

i

i

P

• A phosphorylation cascade

A relay moleculeactivates protein kinase 1.1

2 Active protein kinase 1transfers a phosphate from ATPto an inactive molecule ofprotein kinase 2, thus activatingthis second kinase.

Active protein kinase 2then catalyzes the phos-phorylation (and activation) ofprotein kinase 3.

3

Finally, active proteinkinase 3 phosphorylates aprotein (pink) that brings about the cell’s response tothe signal.

4 Enzymes called proteinphosphatases (PP)catalyze the removal ofthe phosphate groupsfrom the proteins, making them inactiveand available for reuse.

5

SIGNAL TRANSDUCTION PATHWAYS

Like flipping the switch of a mechanical toy which goes full speed when it is turned on and is completely still when turned off.

Inactive until g-protein attaches

Converts ATP into cAMP

Has regulatory factors and catalytic factors

cAMP attaches & breaks regulatory factors away & catalytic factors become energized with the help of ATP (phosphorylation)

Activate phosphorylase to breakdown glycogen into glucose in liver cells & muscle cells.

TransductionChanging the chemical message outside the cell to a message

inside the cell.

Resp

onse

How long does it last?• The cAMP boost does not last without another

surge of epinephrine.• If there is no epinephrine another enzyme,

phosphodiesterase, converts cAMP to AMP.

Like the trigger on a water gun, each time the trigger is pulled the reaction is immediate and temporary; cAMP is produced each time there is a cell signal stimulant (such as epinephrine) but the cAMP does not stay present long.

Maintaining blood glucose levels.Feedback inhibition (negative)

WHAT INSULIN DOES…

Cell Membrane & Water potential

What mechanisms drive molecules across the membrane?

• Passive Transport– Diffusion– Osmosis– Facilitated diffusion

• Active Transport– Sodium Potassium Pump/Electrogenic pump– Cotransport– Exocytosis– Endocytosis

Solutions of Osmosis

•HYPERTONIC:

• Has a higher solute concentration and a lower water potential compared to the solution on the other side of the membrane.

•HYPOTONIC:

• Has a lower solute concentration and a higher water potential than the solution on the other side of the membrane

•ISOTONIC:

• Have equal water potentials

Turgor Pressure• most plant cells live in hypotonic environment• water moves into cells, pushing cell membrane

against cell wall• cell wall is strong enough to resist pressure• pressure from the water is called turgor pressure

Plasmolysis

• plant cells in hypertonic environment• water leaves cells• cell membrane moves away from cell wall• loss of turgor pressure (wilting in plants)

FACILITATED DIFFUSION

CHANNEL PROTEIN

CARRIER PROTEIN

MOVE CHARGED POLAR MOLECULES ACROSS

MEMBRANE

Hydrophillic passageway

EX: aquaporins

EX: Cysteine transporter

ACTIVE TRANSPORT

• Where free energy (often provided by ATP) is used by proteins embedded in the membrane to “move” molecules &/or ions across the membrane & to establish or maintain concentration gradients.

• Membrane proteins are necessary

WHICH MEMBRANE PROTEINS ARE USED?

CARRIER PROTEINS

SODIUM-POTASSIUM PUMP

•Contributes to the membrane potential

•Pumps 3 Na+ out of cell for every 2 K+.

• Creates a positive charge from cytoplasm to extracellular fluid.

• Stores energy in the form of voltage

•Major electrogenic pump of animals

• Proton pump for plants, fungi, & bacteria.

AN EXAMPLE OF ACTIVE TRANSPORT

What is a nerve impulse?

• Nerve impulse is misleading. We will call it an action potential instead

• Can be measured in the same way as electricity is measured– Voltage

• Millivolts

• The conductor of a neuron is the axon– Is covered by a myelin sheath

• Increases the rate at which an action potential passes down an axon.

Resting potential

• Area of a neuron that is ready to send an action potential but is not currently sending one.

• This area is considered polarized– Characterized by the active transport of sodium ions (Na+

) out of the axon cell & potassium ions (K+) into the cytoplasm.

– There are negatively charged ions permanently located in the cytoplasm

– This collection of charged ions leads to a net positive charge outside the axon membrane & negative charge inside.

Action Potential

• Described as a self-propagating wave of ion movements in and out of the neuron membrane

• This is the diffusion of the Na+ & the K+ .– Sodium channels open & then potassium ones do to.

• This is the “impulse” or action potential• It is a nearly instantaneous event occurring in one area of the

axon = depolarization– This area initiates the next area on the axon to open up the channels.

• This action continues down the axon.

• Once an impulse is started at the dendrite end that action potential will self-propagate itself to the far axon end of the cell.

Return to Resting Potential

• Remember that one neuron may send dozens of action potentials in a very short period of time.

• Once an area of the axon sends an action potential it cannot send another until the Na+ & K+ have been restored to their positions at the resting potential.

• Active transport is required to move the ions = repolarization– The time it takes for a neuron to send an action

potential & then repolarize is called: the refractory period of that neuron.

So… what causes diffusion of ions?

• Electrochemical gradient– Electrical force– Concentration gradient

• EX: Na+ concentration inside a resting nerve is much lower than the concentration outside it.– When the cell is stimulated gated channels open & Na+

“fall” down their electrochemical gradient driven by the concentration gradient of the Na+ & the attraction of the cations to the negative side of the membrane.

Human Systems

Villi of the small intestine

Why is your small intestine infested with villi?

Function of villi

• Location of absorption of molecules– All but the fatty acids are absorbed into the capillaries.– Fatty acids are absorbed into the lacteal.

• Lacteal is a vessel that is part of the lymphatic system

• Villi are thin for easy absorption & has an abundance of capillaries and lymph vessels.

• All absorbed molecules are taken to body cells by the circulatory system

• Nutrient molecule can be used for energy (glucose) or as a component to build a larger molecule (amino acids).– The process of building a bigger molecule is called: assimilation

Absorption vs Assimilation

• Absorption occurs when the food enters the body as the food molecules pass through a layer of cells and into the bodies tissues. This occurs in the small intestine which has many villi that are specialized for absorption.

• Assimilation occurs when the food molecules becomes part of the bodies tissue. Therefore, absorption is followed by assimilation.

The Human Heart“Pumps Your Blood”

Valves close to prevent backflow

Closing of the valves produces the “lub dub” sound of you heart

arterioles

venules

Why is the muscle thicker at the left ventricle?

Where would you suppose the highest blood pressure is and why?

Where would you suppose the lowest blood pressure is and why?

The aorta because this is the first place blood travels from the heart pumping it out.

Veins- this is the last area blood travels before entering the heart again. They have valves to prevent back flow

Control of your heart rate

• Hearts are made of muscle tissue; cardiac muscle.– Contracts & relaxes = myogenic muscle contraction

• Mass of tissue in the right atrium known as the sinoatrial node (SA node)– Acts as a pacemaker by sending electrical signals for the

artrias to contract (aka stimulate the myogenic contraction)• 2nd mass is known as the atrioventricular node (AV

node)– On a 0.1 second delay from the SA node in which it sends a

signal for both ventricles to contract.

What happens during exercise?

• Increased demand for oxygen so heart beat speeds up.

• Also an increased build up of CO2 in the bloodstream.

• The medulla chemically senses the rise of CO2

– sends signal through the cardiac nerve to the SA node to increase your heart rate

– Later sends another signal to decrease heart rate through the vagus nerve

Adrenaline

• Chemical that is able to influence your heart rate.

• High stress times and times of excitement triggers the adrenal glands to release adrenaline into your bloodstream.

• The SA node “fires” more frequently causing an increase in your heart rate.

The right atrium's where the process begins, Where the C02 blood enters the heart Through the tricuspid valve to the right ventricle The pulmonary artery and lungs. Once inside the lungs it dumps its carbon dioxide And picks up its oxygen supply Then it's back to the heart through the pulmonary vein Through the atrium and left ventricle."

"Pump, pump, pumps your blood.

"The aortic valve’s where the blood leaves the heart Then it's channeled to the rest of the bod

The arteries, arterioles, and capillaries too Bring the oxygenated blood to the cells The tissues and the cells trade off waste and CO2

Which is carried through the venules and the veins Through the larger vena cava to the atrium and lungs And we're back to where we started in the heart.

Pump, pump, pump, pumps your blood

Pump, pump, pumps your blood.