ch 03 lecture_presentation_a

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2016 Pearson Education, Inc.

PowerPoint Lecture Slidesprepared byKaren Dunbar KareivaIvy Tech Community College Annie Leibovitz/Contact Press ImagesChapter 3 Part A

Cells:The Living Units

Why This MattersUnderstanding the structure of the bodys cells explains why the permeability of the plasma membrane can affect treatment 2016 Pearson Education, Inc.

2016 Pearson Education, Inc.Video: Why This Matters

3.1 Cells: The Living UnitsCell theoryA cell is the structural and functional unit of life How well the entire organism functions depends on individual and combined activities of all of its cellsStructure and function are complementaryBiochemical functions of cells are dictated by shape of cell and specific subcellular structuresContinuity of life has cellular basisCells can arise only from other preexisting cells 2016 Pearson Education, Inc.

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3.1 Cells: The Living UnitsCell diversityOver 200 different types of human cellsTypes differ in size, shape, and subcellular components; these differences lead to differences in functions 2016 Pearson Education, Inc.

Figure 3.1 Cell diversity.ErythrocytesFibroblastsEpithelial cellsSkeletalmusclecellSmoothmuscle cellsNerve cellMacrophageFat cellSpermCell of reproductionCell that storesnutrientsCells that connect body parts, form linings,or transport gasesCells that move organs and body partsCell that gathers information and controlsbody functionsCell that fightsdisease 2016 Pearson Education, Inc.

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3.1 Cells: The Living Units Generalized cell All cells have some common structures and functionsHuman cells have three basic parts: Plasma membrane: flexible outer boundary Cytoplasm: intracellular fluid containing organelles Nucleus: DNA containing control center 2016 Pearson Education, Inc.

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Figure 3.2 Structure of the generalized cell.

ChromatinSmooth endoplasmicreticulum NucleolusMitochondrionLysosomeCentriolesCentrosomematrixPeroxisomeSecretion beingreleased from cellby exocytosisGolgi apparatusRibosomesRoughendoplasmicreticulumNuclear envelopeNucleusPlasmamembraneCytoplasm

Cytoskeletalelements Microtubule Intermediatefilaments 2016 Pearson Education, Inc.

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Extracellular MaterialsSubstances found outside cellsClasses of extracellular materials include:Extracellular fluids (body fluids), such as:Interstitial fluid: cells are submersed (bathed) in this fluidBlood plasma: fluid of the bloodCerebrospinal fluid: fluid surrounding nervous system organsCellular secretions (e.g., saliva, mucus)Extracellular matrix: substance that acts as glue to hold cells together 2016 Pearson Education, Inc.

Part 1 Plasma MembraneActs as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF)Plays dynamic role in cellular activity by controlling what enters and what leaves cellAlso known as the cell membrane 2016 Pearson Education, Inc.

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3.2 Structure of Plasma MembraneConsists of membrane lipids that form a flexible lipid bilayerSpecialized membrane proteins float through this fluid membrane, resulting in constantly changing patternsReferred to as fluid mosaic (made up of many pieces) patternSurface sugars form glycocalyxMembrane structures help to hold cells together through cell junctions 2016 Pearson Education, Inc.

Figure 3.3 The plasma membrane. Extracellular fluid(watery environmentoutside cell)CholesterolGlycolipidGlycoproteinPolar head of phospholipid moleculeNonpolar tail of phospholipid moleculeGlycocalyx(carbohydrates)Lipid bilayercontaining proteinsOutward-facinglayer ofphospholipidsInward-facing layer of phospholipidsFilament of cytoskeletonPeripheral proteinsIntegral proteinsCytoplasm (watery environmentinside cell)Functions of thePlasma Membrane: Mechanical barrier: Separates two of the bodys fluid compartments. Selective permeability: Determines manner in which substances enter or exit the cell. Electrochemical gradient: Generates and helps to maintain the electrochemical gradient required for muscle and neuron function. Communication: Allows cell-to-cell recognition (e.g., of egg by sperm) and interaction. Cell signaling: Plasma membrane proteins interact with specific chemical messengers and relay messages to the cell interior.


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Animation: Membrane Structure 2016 Pearson Education, Inc.

Membrane LipidsLipid bilayer is made up of:75% phospholipids, which consist of two parts:Phosphate heads: are polar (charged), so are hydrophilic (water-loving)Fatty acid tails: are nonpolar (no charge), so are hydrophobic (water-hating)5% glycolipidsLipids with sugar groups on outer membrane surface20% cholesterolIncreases membrane stability 2016 Pearson Education, Inc.

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Membrane ProteinsAllow cell communication with environmentMake up about half the mass of plasma membrane Most have specialized membrane functionsSome float freely, and some are tethered to intracellular structuresTwo types:Integral proteins; peripheral proteins 2016 Pearson Education, Inc.

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Membrane Proteins (cont.)Integral proteinsFirmly inserted into membraneMost are transmembrane proteins (span membrane)Have both hydrophobic and hydrophilic regionsHydrophobic areas interact with lipid tailsHydrophilic areas interact with waterFunction as transport proteins (channels and carriers), enzymes, or receptors 2016 Pearson Education, Inc.

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Membrane Proteins (cont.)Peripheral proteinsLoosely attached to integral proteins Include filaments on intracellular surface used for plasma membrane supportFunction as:EnzymesMotor proteins for shape change during cell division and muscle contractionCell-to-cell connections 2016 Pearson Education, Inc.

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Figure 3.4 Membrane proteins perform many tasks. A protein (left) that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute. Some transport proteins (right) hydrolyze ATP as an energy source to actively pump substances across the membrane. A membrane protein exposed to the outside of the cell may have a binding site that fits the shape of a specific chemical messenger, such as a hormone. When bound, the chemical messenger may cause a change in shape in the protein that initiates a chain of chemical reactions in the cell. Elements of the cytoskeleton (cells internal supports) and the extracellular matrix (fibers and other substances outside the cell) may anchor to membrane proteins, which helps maintain cell shape and fix the location of certain membrane proteins. Others play a role in cell movement or bind adjacent cells together. A membrane protein may be an enzyme with its active site exposed to substances in the adjacent solution. A team of several enzymes in a membrane may catalyze sequential steps of a metabolic pathway as indicated (left to right) here. Membrane proteins of adjacent cells may be hooked together in various kinds of intercellular junctions. Some membrane proteins (cell adhesion molecules or CAMs) of this group provide temporary binding sites that guide cell migration and other cell-to-cellinteractions. Some glycoproteins (proteins bonded to short chains of sugars which help to makeup the glycocalyx) serve as identificationtags that are specifically recognized by other cells.Intercellular joiningCell-cell recognitionAttachment to the cytoskeletonand extracellular matrixReceptors for signal transductionTransportEnzymatic activityGlycoproteinCAMsEnzymesATPSignalReceptor


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Figure 3.4a Membrane proteins perform many tasks. Transport A protein (left) that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute. Some transport proteins (right) hydrolyze ATP as an energy source to actively pump substances across the membrane.ATP 2016 Pearson Education, Inc.

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Animation: Transport Proteins 2016 Pearson Education, Inc.

Figure 3.4b Membrane proteins perform many tasks. Receptors for signal transduction A membrane protein exposed to the outside of the cell may have a binding site that fits the shape of a specific chemical messenger, such as a hormone. When bound, the chemical messenger may cause a change in shape in the protein that initiates a chain of chemical reactions in the cell.SignalReceptor


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Animation: Receptor Proteins 2016 Pearson Education, Inc.

Figure 3.4c Membrane proteins perform many tasks. Elements of the cytoskeleton (cells internal supports) and the extracellular matrix (fibers and other substances outside the cell) may anchor to membrane proteins, which helps maintain cell shape and fix the location of certain membrane proteins. Others play a role in cell movement or bind adjacent cells together.Attachment to the cytoskeletonand extracellular matrix 2016 Pearson Education, Inc.

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Animation: Structural Proteins 2016 Pearson Education, Inc.

Figure 3.4d Membrane proteins perform many tasks. Enzymatic activity A membrane protein may be an enzyme with its active site exposed to substances in the adjacent solution. A team of several enzymes in a membrane may catalyze sequential steps of a metabolic pathway as indicated (left to right) here.Enzymes


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Animation: Enzymes 2016 Pearson Education, Inc.

Figure 3.4e Membrane proteins perform many tasks.

Intercellular joining Membrane proteins of adjacent cells may be hooked together in various kinds of intercellular junctions. Some membrane proteins (cell adhesion molecules or CAMs) of this group provide temporary binding sites that guide cell migration and other cell-to-cell interactions.CAMs 2016 Pearson Education, Inc.

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Figure 3.4f Membrane proteins perform many tasks. Cell-cell recognition Some glycoproteins (proteins bonded to short chains of sugars which help to makeup the glycocalyx) serve as identificationtags that are specifically recognized by other cells.Glycoprotein


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GlycocalyxConsists of sugars (carbohydrates) sticking out of cell surfaceSome sugars are attached to lipids (glycolipids) and some to proteins (glycoproteins)Every cell type has different patterns of this sugar coatingFunctions as specific biological markers for cell- to-cell recognitionAllows immune system to recognize self vs. nonself 2016 Pearson Education, Inc.

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Clinical Homeostatic Imbalance 3.1Glycocalyx of some cancer cells can change so rapidly that the immune system cannot recognize the cell as being damaged.Mutated cell is not destroyed by immune system so it is able to replicate 2016 Pearson Education, Inc.

Cell JunctionsSome cells are free (not bound to any other cells)Examples: blood cells, sperm cellsMost cells are bound together to form tissues and organsThree ways cells can be bound to each otherTight junctions Desmosomes Gap junctions 2016 Pearson Education, Inc.

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Cell Junctions (cont.)Tight junctionsIntegral proteins on adjacent cells fuse to form an impermeable junction that encircles whole cellPrevent fluids and most molecules from moving in between cells Where might these be useful in body? 2016 Pearson Education, Inc.

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Figure 3.5a Cell junctions. InterlockingjunctionalproteinsIntercellularspaceBasement membraneMicrovilliIntercellularspacePlasma membranesof adjacent cellsTight junctions: Impermeablejunctions that form continuousseals around the cells preventmolecules from passing throughthe intercellular space.


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Cell Junctions (cont.)DesmosomesRivet-like cell junction formed when linker proteins (cadherins) of neighboring cells interlock like the teeth of a zipperLinker protein is anchored to its cell through thickened button-like areas on inside of plasma membrane called plaquesKeratin filaments connect plaques intercellularly for added anchoring strengthDesmosomes allow give between cells, reducing the possibility of tearing under tensionWhere might these be useful in body? 2016 Pearson Education, Inc.

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Figure 3.5b Cell junctions. PlaqueIntercellular spaceLinkerproteins(cadherins)Intermediatefilament (keratin)MicrovilliIntercellularspacePlasma membranesof adjacent cellsDesmosomes: Anchoring junctionsthat bind adjacent cells together actlike molecular Velcro and also helpform an internal tension-reducingnetwork of fibers.

Basement membrane 2016 Pearson Education, Inc.

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Cell Junctions (cont.)Gap junctionsTransmembrane proteins (connexons) form tunnels that allow small molecules to pass from cell to cellUsed to spread ions, simple sugars, or other small molecules between cellsAllows electrical signals to be passed quickly from one cell to next cellUsed in cardiac and smooth muscle cells 2016 Pearson Education, Inc.

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Figure 3.5c Cell junctions. IntercellularspaceChannelbetween cells(formed byconnexons)Basement membraneMicrovilliIntercellularspacePlasma membranesof adjacent cellsGap junctions: Communicatingjunctions that allow ions and smallmolecules to pass are particularlyimportant for communication inheart cells and embryonic cells.


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How do substances move across the plasma membrane?Plasma membranes are selectively permeableSome molecules pass through easily; some do notTwo ways substances cross membranePassive processes: no energy requiredActive processes: energy (ATP) required 2016 Pearson Education, Inc.

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3.3 Passive Membrane TransportPassive transport requires no energyTwo types of passive transportDiffusionSimple diffusionCarrier- and channel-mediated facilitated diffusionOsmosisFiltrationType of transport that usually occurs across capillary walls 2016 Pearson Education, Inc.

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DiffusionCollisions between molecules in areas of high concentration cause them to be scattered into areas with less concentrationDifference is called concentration gradientDiffusion is movement of molecules down their concentration gradients (from high to low)Energy is not requiredSpeed of diffusion is influenced by size of molecule and temperature 2016 Pearson Education, Inc.

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Figure 3.6 Diffusion.Dye pelletDiffusion occurringDye evenly distributed


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Diffusion (cont.)Molecules have natural drive to diffuse down concentration gradients that exist between extracellular and intracellular areasPlasma membranes stop diffusion and create concentration gradients by acting as selectively permeable barriers 2016 Pearson Education, Inc.

Clinical Homeostatic Imbalance 3.2If plasma membrane is severely damaged, substances diffuse freely into and out of cell, compromising concentration gradientsExample: burn patients lose precious fluids, proteins, and ions that weep from damaged cells


Diffusion (cont.)Nonpolar, hydrophobic lipid core of plasma membrane blocks diffusion of most moleculesMolecules that are able to passively diffuse through membrane include:Lipid-soluble and nonpolar substancesVery small molecules that can pass through membrane or membrane channelsLarger molecules assisted by carrier molecules 2016 Pearson Education, Inc.

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Diffusion (cont.)Simple diffusionNonpolar lipid-soluble (hydrophobic) substances diffuse directly through phospholipid bilayerExamples: oxygen, carbon dioxide, fat-soluble vitamins 2016 Pearson Education, Inc.

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Animation: Diffusion 2016 Pearson Education, Inc.

Figure 3.7a Diffusion through the plasma membrane.Extracellular fluidLipid-solublesolutesCytoplasmSimple diffusionof fat-solublemolecules directlythrough the phospholipid bilayer


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Diffusion (cont.)Facilitated diffusionCertain hydrophobic molecules (e.g., glucose, amino acids, and ions) are transported passively down their concentration gradient by:Carrier-mediated facilitated diffusionSubstances bind to protein carriersChannel-mediated facilitated diffusionSubstances move through water-filled channels


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Diffusion (cont.)Carrier-mediated facilitated diffusionCarriers are transmembrane integral proteinsCarriers transport specific polar molecules, such as sugars and amino acids, that are too large for membrane channelsExample of specificity: glucose carriers will carry only glucose molecules, nothing elseBinding of molecule causes carrier to change shape, moving molecule in processBinding is limited by number of carriers presentCarriers are saturated when all are bound to molecules and are busy transporting 2016 Pearson Education, Inc.

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Figure 3.7b Diffusion through the plasma membrane.Lipid-insoluble solutes(such as sugars oramino acids)Shape change releases solutesCarrier-mediated facilitateddiffusion via protein carrierspecific for one chemical; bindingof substrate causes transportprotein to change shape


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Diffusion (cont.)Channel-mediated facilitated diffusionChannels with aqueous-filled cores are formed by transmembrane proteinsChannels transport molecules such as ions or water (osmosis) down their concentration gradient Specificity based on pore size and/or chargeWater channels are called aquaporinsTwo types:Leakage channelsAlways openGated channelsControlled by chemical or electrical signals 2016 Pearson Education, Inc.

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Figure 3.7c Diffusion through the plasma membrane.Small lipid-insolublesolutesChannel-mediated facilitated diffusion through a channel protein; mostly ions selected on basis of size and charge


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Diffusion (cont.)OsmosisMovement of solvent, such as water, across a selectively permeable membrane Water diffuses through plasma membranesThrough lipid bilayer (even though water is polar, it is so small that some molecules can sneak past nonpolar phospholipid tails)Through specific water channels called aquaporins (AQPs)Flow occurs when water (or other solvent) concentration is different on the two sides of a membrane 2016 Pearson Education, Inc.

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Figure 3.7d Diffusion through the plasma membrane.WatermoleculesLipidbilayerAquaporinOsmosis, diffusion ofa solvent such as water through a specific channel protein (aquaporin) or through the lipid bilayer


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Diffusion (cont.)Osmolarity: measure of total concentration of solute particlesWater concentration varies with number of solute particles because solute particles displace water moleculesWhen solute concentration goes up, water concentration goes down, and vice versaWater moves by osmosis from areas of low solute (high water) concentration to high areas of solute (low water) concentration


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Diffusion (cont.)When solutions of different osmolarity are separated by a membrane permeable to all molecules, both solutes and water cross membrane until equilibrium is reachedEquilibrium: Same concentration of solutes and water molecules on both sides, with equal volume on both sides 2016 Pearson Education, Inc.

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Figure 3.8a Influence of membrane permeability on diffusion and osmosis.Membrane permeable to both solutes and waterSolute and water molecules move down their concentration gradients inopposite directions. Fluid volume remains the same in both compartments.Leftcompartment:Solution withlower osmolarityRightcompartment:Solution with greater osmolarityBoth solutions have thesame osmolarity: volumeunchangedSolutemolecules(sugar)FreelypermeablemembraneSoluteH2O


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Diffusion (cont.)When solutions of different osmolarity are separated by a membrane that is permeable only to water, not solutes, osmosis will occur until equilibrium is reachedSame concentration of solutes and water molecules on both sides, with unequal volumes on both sides


Figure 3.8b Influence of membrane permeability on diffusion and osmosis.Membrane permeable to water, impermeable to solutesSolute molecules are prevented from moving but water moves by osmosis.Volume increases in the compartment with the higher osmolarity.H2OLeftcompartmentRightcompartmentSolutemolecules(sugar)SelectivelypermeablemembraneBoth solutions have identicalosmolarity, but volume of thesolution on the right is greaterbecause only water is free to move


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Diffusion (cont.)Movement of water causes pressures:Hydrostatic pressure: pressure of water inside cell pushing on membraneOsmotic pressure: tendency of water to move into cell by osmosisThe more solutes inside a cell, the higher the osmotic pressure 2016 Pearson Education, Inc.

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Animation: Osmosis 2016 Pearson Education, Inc.

Diffusion (cont.)A living cell has limits to how much water can enter itWater can also leave a cell, causing cell to shrinkChange in cell volume can disrupt cell function, especially in neurons


Diffusion (cont.)TonicityAbility of a solution to change the shape or tone of cells by altering the cells internal water volume Isotonic solution has same osmolarity as inside the cell, so volume remains unchangedHypertonic solution has higher osmolarity than inside cell, so water flows out of cell, resulting in cell shrinkingShrinking is referred to as crenationHypotonic solution has lower osmolarity than inside cell, so water flows into cell, resulting in cell swellingCan lead to cell bursting, referred to as lysing 2016 Pearson Education, Inc.

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Figure 3.9 The effect of solutions of varying tonicities on living red blood cells.Isotonic solutionsHypertonic solutionsHypotonic solutionsCells retain their normal size andshape in isotonic solutions (samesolute/water concentration asinside cells; water moves inand out).Cells lose water by osmosis andshrink in a hypertonic solution(contains a higher concentrationof nonpenetrating solutes thanare present inside the cells).Cells take on water by osmosisuntil they become bloated andburst (lyse) in a hypotonicsolution (contains a lower concentration of nonpenetratingsolutes than are presentinside cells). 2016 Pearson Education, Inc.

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Clinical Homeostatic Imbalance 3.3Intravenous solutions of different tonicities can be given to patients suffering different ailmentsIsotonic solutions are most commonly given when blood volume needs to be increased quicklyHypertonic solutions are given to edematous (swollen) patients to pull water back into bloodHypotonic solutions should not be given because they can result in dangerous lysing of red and white blood cells 2016 Pearson Education, Inc.