The Cellular Level of Organization

The Cellular Level of OrganizationChapter 1 Section 1: Parts of a CellTypical Structures Found in a Cell

Plasma Membraneforms a cells flexible outer surfaceseparates inside from outsideacts as a selective barrier that regulates what gets in or out of cellplays key role in communication with other cells

Plasma MembraneFluid Mosaic Modelresembles an ever-moving sea of fluid lipids that has large proteins bobbing along throughout the lipids

Fluid Mosaic Model of Plasma Membranemembrane proteins either float around like icebergs or are anchored at specific locations

The Lipid Bilayerbasic structure of plasma membranemade of 2 back-to-back layers using 3 types of lipidsasymmetric

Lipid Bilayer1st LipidPhospholipids75% of lipid membranelipids with phosphate groups

Lipid Bilayer2nd Lipid2. Cholesterol20% of lipid membranea steroid makes bilayer less fluidweakly amphipathic (-OH group on 1 end can form H-bonds)

Lipid Bilayer3rd LipidGlycolipids~5% of membrane lipidslipid with attached carbohydrate group stick out into extracellular space

Phospholipids are Amphipathic

Phospholipid Bilayer

like likes likehydro: waterphilic: lovingphobic: hatingPolar molecules hydrophilicNonpolar molecules hydrophobic

Arrangement of Membrane ProteinsIntegral Membrane Proteinsembedded in membranemost are transmembrane: protrude both into cytosol & ECFamphipathicPeripheral Proteinloosely assc with polar heads of membrane lipids or with integral proteinsinner or outer surface of membraneMembrane Proteins

Glycoproteinsproteins with carbohydrate groups attached to the ends that protrude into ECFthese carbohydrate groups are oligosaccharides (few-sugars): straight or branched chains of 2 60 monosaccharidesGlycoproteins

Glycocalyxcarbohydrate portions of glycolipids + glycoproteins = glycocalyxacts like name tag for cells to recognize each other

Glycocalyxenables cells to adhere to each otherprotects some cells from being digested by enzymes in ECF

Types & Functions of Membrane Proteins: Integral ProteinsION CHANNELS are holes or pores thru which specific ions flow in or out of cellmost are very selectiveExamples: K+ ion channels

Types of Integral Membrane Proteins2. TRANSPORTERSselectively move a polar substance (like water) across the plasma membranewater transporters called aquaporinsExample: aquaporin

Types of Integral Membrane ProteinsRECEPTORSserve as cellular recognition sitesrecognizes & binds specific type of moleculethe specific molecule that binds to a receptor protein is called a ligandReceptor Proteins

Types of Integral Membrane Proteins4. ENZYMEScatalyze specific chemical reactions at inside or outside cell

Types of Integral Membrane Proteins5. LINKERSintegral proteins anchor proteins in the plasma membranes of neighboring cells or to protein filaments inside & outside the cell

Cell-Identity Markersglycoproteins or glycolipidsExample: ABO blood type markers

Selective Permeabilitysome substances can easily pass thru, others not at alllipid-bilayer nonpolar sopermeable to small nonpolar substancesimpermeable to polar substances

Water is an exceptionis polarsmall amts cross plasma membraneGradients Across the Plasma Membraneselective permeability across plasma membrane maintains different concentrations of certain substances on either side of plasma membraneconcentration gradient: a difference in the concentration of a chemical from 1 place to another

Gradients across the Plasma Membranebecause several of the substances kept in different concentrations on either side of membrane have (+) or (-) charges there is an electrical gradient across the membrane

typically, inside surface of membrane is slightly (-) & outside surface of membrane is slightly (+)Gradients across thePlasma Membranea difference in charge across membrane is called: membrane potential

just like a battery where there is separation of charge used as source of energy so too a membrane potential can be thought of as potential energy for cell to move substances in or out of cell

The combined influence of the concentration gradient & membrane potential on movement of a particular ion is referred to as its electrochemical gradient

Chapter 3 Section 2Transport Across the Plasma Membrane

Essential QuestionWhat is the main difference between primary & secondary active transport mechanisms?Kinetic Energy Transportdiffusion is a passive process in which the random mixing of particles in a solution occurs because of the particles kinetic energy

solute: dissolved substances

solvent: liquid that does dissolvingDiffusionsolutes move down their concentration gradient until they are evenly distributedDiffusionsolute particles continue to move due to their kinetic energy

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html Factors that Influence Rate of Diffusion acrossPlasma MembraneSteepness of Concentration Gradientgreater the difference between 2 sides, higher rate of diffusionsteepness of electrochemical gradient determines rate of diffusionFactors that Influencethe Rate of Diffusion acrossPlasma Memebrane2. Temperaturehigher temperature higher KE of particles faster it diffusesall diffusion processes go faster when person has a feverFactors that Influence Rate of Diffusion acrossPlasma Membrane

3. Mass of the Solute Diffusinglarger masses diffuse slower than smaller massesFactors that Influence Rate of Diffusion acrossPlasma Membrane4. Surface Area larger membrane surface area, faster the diffusion rateFactors that Influence Rate of Diffusion acrossPlasma Memebrane5. Diffusion Distancegreater distance over which diffusion must occur, the longer it takesplasma membranes very thin so diffusion is rapid, processes that thicken that space (autoimmune disease) slow down rateWhat Diffuses Across Plasma Membranenonpolar, hydrophobic, small molecules:O2 & CO2 gasesLipids (fatty acids, steroids)fat-soluble vitamins:A, D, E, K

Facilitated Diffusiondiffusion through an integral membrane protein from side with higher concentration to side with lower concentration

Facilitated Diffusion

Facilitated Diffusiontransporters very specificpassive process (no nrg output by cell)# of transporters limited so there is an upper limit to the amount that can cross membrane: called a transport maximum or Tmaxonce all transporters occupied the diffusion rate cannot increase

Facilitated Diffusionhttp://programs.northlandcollege.edu/biology/Biology1111/animations/passive3.swf Gated Channelswhen part of the channel protein acts as a plug or gate changing shape to open pore & in another shape to close it

Gated Channelssome randomly alternate between open & closedsome regulated by chemical or electrical changes inside & outside cell

Voltage Gated Channels

Osmosisnet movement of water thru selectively permeable membranewater can move across membrane but solute cannotwater moves down waters concentration gradient

Osmosisduring osmosis water molecules pass through a plasma membrane in 2 ways:1. moving thru lipid bilayer2. moving thru aquaporins

Isotonic Solutionsconcentration of solutes that cannot cross membrane same on both sides of membranein human body isotonic solution is 0.9% NaCl (normal saline)allows cells to maintain normal shape & volume

Hypotonic Solutionsolution has lower concentration of solutes than the cytosol (higher concentration of water outside cell)water molecules enter cell faster than they leave cell volume enlarges cell bursts (if RBC called hemolysis)

Hypertonic Solutionsolution has a higher concentration of solute than cytosolwater molecules will move out of cell into ECFRBCs will shrink, called crenation

Crenation

Medical Uses of Isotonic SolutionsIV solutions (intravenous) are isotonic so RBCs will not change shape or volumeexample : 0.9% NaClMedical Uses for Hypotonic Solutionsgiven orally or IV used to treat dehydrationwater & sports drinks hypotonicMedical Uses for Hypertonic Solutionsused to treat cerebral edema (increased interstitial fluid around the brain)example: mannitolcauses excess water in interstitial fluid into blood kidney for excretion in urineActive Transportused for polar solutes that must enter or leave cells need to move uphill against their concentration gradientsrequires cell to spend some energy moving things against concentration gradients

Primary Active Transportnrg required comes from hydrolysis of ATP (adenosine triphosphate)

ATP Pumps

a typical body expends 40% of its ATP on primary active transportmost prevalent primary active transport mechanism is the sodium-potassium pump (Na/K pump)part of the pump acts as enzyme ATPase (hydrolyzes ATP) so pump also called: sodium-potassium-ATPase pump

Steps in Na+/K+/ATPase Pump(3) Na+ in cytosol bind to pumpthat triggers hydrolysis of 1 ATP; phosphate removed attached to pump which changes shape of the pump causing all 3 Na+ to be expelled out into the ECF. This new shape also favors the binding of 2 K+ from ECF onto pumpSteps in Na+/K+/ATPase Pump

Steps in Na+/K+/ATPase Pump3. binding K+ triggers release of that phosphate group that attached itself in Step 1, releasing it causes change in shape of protein pump4. when shape changes in Step 3, the 2 K+ are released into the cytosol. Pump now ready to attach 3 Na+ and start over

Na+/K+/ATPase Pumphttp://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html Why is the Na+/K+/ATPase Pump so Important?must maintain the different concentrations of Na+ and K+ in order for cells to maintain normal volume & for ability of some cells to generate electrical signals (action potentials in neurons)Secondary Active Transportpotential electricalchemical nrg stored in concentration gradient of Na+ or H+ is used to push substances across membrane uphill (against their concentration gradient)these concentration gradients established by primary active transport so the 2 active transport indirectly uses ATPSecondary Active Transport

Symporterstransporters that move 2 substances in same direction

Antiporterstransporters that move 2 substances in opposite directions across the plasma membrane

Transport in Vesiclesvesicle: small spherical sac formed by membrane

Endocytosismaterials move into cell in a vesicle formed by plasma membrane3 Types:Receptor-mediated endocytosisPhagocytosisPinocytosis Receptor-Mediated Endocytosis

Receptor-Mediated Endocytosis

Phagocytosis

Macrophage Phagocytosing Bacteria

Pinocytosismeans cell-drinkingtiny droplets of ECF taken into cellno receptor proteins involved

Exocytosisreleases material from cellall cells do it but is most important in:Secretory cells that release digestive enzymes, hormones, mucusend of axons on neuron that release neurotransmittersExocytosis

segments of plasma membrane lost in endocytosis and gained in exocytosisusually evens outif necessary ER makes moreChapter 3 Section 3Cytoplasm & OrganellesEssential Question:How would you describe the structure & function of the cytoplasm and main organelles of the cell?Cytosolsame as intracellular fluidfluid portion of cytoplasm55% of cell volumecomposition varies from cell to cell: mostly it is 75 -90% water, rest is dissolved & suspended componentsions , glucose, a.a., fatty acids, lipids, proteins, ATP, waste productsCytosolsite of many chemical reactionsglycolysis

Cytoskeletona network of protein filaments that extends throughout the cytosol

3 Types of CytoskeletonMicrofilaments thinnest of the 3 made of protein actin most prevalent at periphery of cell 2 functions:1. movement 2. support

Microfilamentsalso provide mechanical support for microvilli : fingerlike projections of plasma membrane; function is to greatly increase surface areaabundant in cells of small intestine that absorb

Cytoskeleton2. Intermediate Filaments medium-sized exceptionally strong (used in parts of cell under mechanical stress) also function to anchor nucleus & attach cells to each otherIntermediate Filaments

Microtubuleslargest of cytoskeleton componentsLong, unbranched hollow tubesmade mostly of protein tubulinmade in centrosomes an organelle near nucleusfunction: cell shape, movement of organelles, chromosomes, flagella, & ciliaMicrotubules

Cilia

Flagella

Ribosomes sites of protein synthesismade of rRNA + >50 proteins2 subunits: made separately in nucleolus apart until making protein

Ribosomes found:in cytoplasm called free ribosomesmake proteins used in cytosolattached to membrane of RERmake proteins to be used by specific organelles or to be exported from cellRibosomes

Endoplasmic ReticulumERnetwork of membranes in form of flattened sacs or tubulesextend from its connection to nuclear envelope to throughout the cytoplasm >1/2 membranous surfaces w/in most cellstypes: rough or smoothRough ER = RERcontinuous with nuclear membrane folded in series of flattened sacsouter surface RER studded with ribosomes which make proteins that then travel thru spaces of ER for processing & sortingProteins made in RERglycoproteins (proteins + carbohydrate)lipoproteins membrane (proteins + lipids)packaged inside vesicles Golgi or directly to export

RER

Smooth ER = SERmakes fatty acids (fa) & steroidsinactivates (detoxifies) drugs & other harmful substancesstores & releases Ca++ that trigger muscle contractionsSER & Drug Tolerance1 of functions of liver is to detoxify& it does this because liver cells, hepatocytes, have a lot of SERprolonged use of a medication or illegal drug causes hepatocytes to increase the amount of SER to accommodate detoxifying extra drug & so person has to take more & more drug to get same affectSER

Hepatocytes

SER or RER?

Golgi Complex Functionsmodifies, sorts, packages, & transports proteins received from RERforms secretory vesicles that discharge processed proteins via exocytosis into ECF; vesicle membrane then added to plasma membraneGolgi Complex

Lysosomes Functiondigest substances that enter cell via endocytosis & transport final products of digestion into cytosolautophagy (digestion of worn out organelles)autolysis (digest entire cell)extracellular digestionLysosomes

Mitochondria generate ATP thru reactions of aerobic cellular respirationhave a double membraneboth similar to plasma membranemitochondrial DNA (maternal)replicate when demand for ATP increases

Mitochondria

NUCLEUSFunctions:contains genetic informationcontrols cellular structurecontrols cell activities produces ribosomes in nucleolusNUCLEUSusually most prominent structure in cellmost human cells have 1mature RBC have 0mature WBC have multipledbl membrane surrounds it, called nuclear envelopeholes in it called nuclear pores

NUCLEOLUSprominent, dark, spherical structure in nucleussite of manufacture of subunits of ribosomesdisperse & disappear during cell division

Name & Function Please1.2.

3.4.

5.6.

7.8.

9.10.

Chapter 3 Section 4Cell Division

Essential Question: How would you explain the stages and significance of somatic & reproductive cell division?Definitions somatic cell: any cell other than ova or spermmitosis: nuclear division of somatic cellcytokinesis: division of cytoplasmgametes: sex cells, ova or spermmeiosis: nuclear division of gametesDefinitionshomologous chromosomes: 2 copies of same chromosomes: 1 maternal, 1 paternal

haploid: having only 1 set of chromosomes as found in gametes, designated n

diploid: having 2 sets of chromosomes as found in somatic cells, designated 2nCell Cycle

Cell CycleG0 when cells are not going to go thru cell division again or not for very long periods of time

typically:G1 8 10 hoursS 8 hoursG2 4 6 hours

Definitions centromere: constricted portion of a duplicated chromosome; serves as point of attachment for microtubules that pull chromatids apart during anaphase

kinetochore: protein complex attached to outside of centromere

Definitionsmitotic spindle: collective term for a football-shaped assembly of microtubules that is responsible for movement of chromosomes during mitosissister chromatids: pair of identical DNA strands that are joined at the centromere and separate during mitosis becoming a chromosome of 1 of 2 daughter cellsChromosomes

Mitosis

Mitotis Phases: ProphaseProphaseEarly Prophasechromatin condenses & shorten into chromosomes visible under light microscope made up of sister chromatids with centromere

Late Prophasemitotic spindle begins to form extending to poles of cell

Metaphase microtubules align the centromeres at exact center of mitotic spindlecalled metaphase plate

Anaphase centromeres split & sister chromatids move toward opposite polesonce separated chromatids called chromosomes

Telophaseidentical sets of chromosomes now at opposite poles of cellchromosomes uncoil chromatinnuclear envelope re-formscleavage furrow starts to form

Cytokinesisdivision of cytoplasm completedcleavage furrow usually midway between poles (actin microfilaments form a contractile ring)organelles on each side

Mitosisstart with parent cell with diploid # chromosomes (46)ends with 2 daughter cells each with a diploid # of chromosomes (46) genetically the same as parent cellName That Stage of Mitosis1.2.

3.4.

5.6.

Control of the Cell CycleCells have 3 choices:Keep going thru Cell Cycleenter G0 Die

Homeostasis is maintained when there is a balance between cell proliferation & cell deathCell Cycle Regulationcyclins are proteins that are responsible for activating enzymes called Cdks (cyclin-dependent protein kinases)Cdks transfer a phosphate group from ATP to a protein which activates the protein; other enzymes remove the phosphate group thus de-activating itCell Cycle Regulationactivation/deactivation of Cdks is crucial to DNA replication, mitosis & cytokinesisactivation of specific cyclin-Cdk complexes responsible for a cell going from G1 S G2 mitosisCell Deathapoptosis: programmed cell deathtrigger from outside or inside cell causes cell-suicide genes to produce enzymes that damage the cell in several waysphagocytes (cells that engulf debris, bacteria; clean-up crew) ingest the dying cellApoptosisremoves unneeded cells during fetal development (like webbing between digits)eliminates potentially harmful cells like cancer cellsTumor-Suppressor Genesproduce proteins that inhibit cell divisiondamage to these genes causes some types of cancerexample: p53 is a tumor-suppressor gene on chromosome 17 which normally arrests cells in G1 & assists in repair of DNA if repair not successful p53 induces apoptosis of that cellabnl in this gene have led to different cancers (breast, colon)

Meiosisfor reproduction of sex cellsmust have haploid # so when ova & sperm unite offspring will have normal diploid # of chromosomesstarts with diploid cell meiosis 4 daughter cells each with a haploid # of chromosomes (23) that are genetically different than original cellMeiosis

Meiosis I: Prophase Ihomologous chromosomes matched up (called synapse) and do a little trading of alleles (crossing over): results in genetic variation: the 4 daughter cells will be genetically different

Crossing Over

Meiosis IMetaphase Ihomologous chromosomes line up on metaphase plateAnaphase Ihomologous chromosomes move to opposite poles Meiosis ITelophase Inuclear envelopes re-formeach nucleus has 23 duplicated chromosomesCytokinesis I2 daughter cells each with n chromosomes (in duplicated state)Meiosis IIProphase II

Metaphase II

Meiosis IIAnaphase II

Telophase II

Meiosis II

Homeostatic Imbalances CancerLarge group of diseases characterized by uncontrolled or abnormal cell proliferationAbnl cells also called:TumorMalignancyNeoplasm Metastasis: cells spread from organ of origin

Causes of CancerCarcinogen: chemical or radiation that causes cancerCarcinogens cause DNA mutations (permanent changes in DNA)Oncogenes: cancer-causing genes Oncogenic Viruses: stimulate abnl proliferation of cells (HPV, HepatitisC)