3 The Cellular Level of Organization

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3 The Cellular Level of Organization. An Introduction to Cells. Cell Theory Developed from Robert Hooke’s research Cells are the building blocks of all plants and animals All cells come from the division of preexisting cells Cells are the smallest units that perform all vital
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3The Cellular Level of OrganizationAn Introduction to Cells
  • Cell Theory
  • Developed from Robert Hooke’s research
  • Cells are the building blocks of all plants and animals
  • All cells come from the division of preexisting cells
  • Cells are the smallest units that perform all vital
  • physiological functions
  • Each cell maintains homeostasis at the cellular level
  • An Introduction to Cells
  • Sex Cells (Germ Cells)
  • Reproductive cells
  • Male sperm
  • Female oocyte (a cell that develops into an egg)
  • Somatic Cells
  • Soma = body
  • All body cells except sex cells
  • Figure 3-1 Anatomy of a Model Cell Plasma membrane Nonmembranous organelles Membranous organellesSecretory vesiclesCentrosome and CentriolesCytoplasm contains two centrioles at right angles; each centriole iscomposed of 9 microtubule triplets in a 9  0 arrayCYTOSOLFunctionsEssential formovement ofchromosomesduring cell division;organization ofmicrotubules incytoskeletonCentrosomeCentriolesFigure 3-1 Anatomy of a Model Cell Plasma membrane Nonmembranous organellesCytoskeleton Membranous organellesProteins organized in fine filaments orslender tubesMicrofilamentFunctionsStrength andsupport;movement ofcellular structuresand materialsMicrotubulePlasma MembraneLipid bilayer containing phospholipids, steroids, proteins, and carbohydratesFreeribosomesFunctionsIsolation;protection;sensitivity;support;controls entryand exit ofmaterialsCytosol (distributesmaterials by diffusion)Figure 3-1 Anatomy of a Model CellMicrovilliMembrane extensionscontaining microfilamentsFunctionIncrease surfacearea to facilitateabsorption of extra-cellular materials Plasma membrane Nonmembranous organelles Membranous organellesFigure 3-1 Anatomy of a Model CellCiliaCilia are long extensionscontaining microtubuledoublets in a 9  2 array (notshown in the model cell) Plasma membraneFunctionMovement of material over cell surface Nonmembranous organelles Membranous organellesProteasomesHollow cylinders of proteolyticenzymes with regulatory proteins at their endsFunctionsBreakdown and recycling of damaged or abnormal intracellular proteins RibosomesRNA  proteins; fixed ribosomesbound to rough endoplasmicreticulum, free ribosomesscattered in cytoplasmFunctionProtein synthesisFigure 3-1 Anatomy of a Model CellGolgi apparatusStacks of flattened membranes(cisternae) containing chambersFunctionsStorage, alteration, and packaging of secretory products and lysosomal enzymesMitochondriaDouble membrane, with innermembrane folds (cristae)enclosing important metabolicenzymesFunctionsProduce 95% of the ATPrequired by the cellEndoplasmic reticulum (ER)Network of membranouschannels extendingthroughout the cytoplasmRough ERmodifies andpackages newlysynthesized proteinsNUCLEUSFunctionsSynthesis of secretoryproducts; intracellularstorage and transportSmooth ERsynthesizes lipids and carbohydratesPeroxisomesVesicles containingdegradative enzymesFunctionsCatabolism of fats and otherorganic compounds,neutralization of toxiccompounds generated inthe process Plasma membrane Nonmembranous organelles Membranous organellesFigure 3-1 Anatomy of a Model Cell Plasma membrane Nonmembranous organelles Membranous organellesPeroxisomesVesicles containingdegradative enzymesFunctionsCatabolism of fats and otherorganic compounds,neutralization of toxic compounds generated in the processFreeribosomesLysosomesVesicles containingdigestive enzymesFunctionsIntracellular removal ofdamaged organelles orpathogensFigure 3-1 Anatomy of a Model CellChromatinNUCLEUSNuclearenvelopeNucleoplasm containingnucleotides, enzymes,nucleoproteins, andchromatin; surrounded by a double membrane,the nuclear envelopeNUCLEOPLASMNucleolus(site of rRNAsynthesis andassembly ofribosomalsubunits)NuclearporeFunctions:Control of metabolism; storage and processing of genetic information;control of proteinsynthesis3-1 Plasma Membrane
  • Extracellular Fluid (Interstitial Fluid)
  • A watery medium that surrounds a cell
  • Plasma membrane (cell membrane) separatescytoplasm from the extracellular fluid
  • Cytoplasm
  • Cytosol = liquid
  • Intracellular structures collectively known as organelles
  • 3-1 Plasma Membrane
  • Functions of the Plasma Membrane
  • Physical Isolation
  • Barrier
  • Regulation of Exchange with the Environment
  • Ions and nutrients enter
  • Wastes eliminated and cellular products released
  • 3-1 Plasma Membrane
  • Functions of the Plasma Membrane
  • Sensitivity to the Environment
  • Extracellular fluid composition
  • Chemical signals
  • Structural Support
  • Anchors cells and tissues
  • 3-1 Plasma Membrane
  • Membrane Lipids
  • Phospholipidbilayer
  • Hydrophilic heads — toward watery environment, both sides
  • Hydrophobic fatty-acid tails — inside membrane
  • Barrier to ions and water — soluble compounds
  • 3-1 Plasma Membrane
  • Membrane Proteins
  • Integral Proteins
  • Within the membrane
  • Peripheral Proteins
  • Bound to inner or outer surface of the membrane
  • 3-1 Plasma Membrane
  • Membrane Proteins
  • Anchoring Proteins (stabilizers)
  • Attach to inside or outside structures
  • Recognition Proteins (identifiers)
  • Label cells as normal or abnormal
  • Enzymes
  • Catalyze reactions
  • 3-1 Plasma Membrane
  • Membrane Proteins
  • Receptor Proteins
  • Bind and respond to ligands (ions, hormones)
  • Carrier Proteins
  • Transport specific solutes through membrane
  • Channels
  • Regulate water flow and solutes through membrane
  • 3-1 Plasma Membrane
  • Membrane Carbohydrates
  • Proteoglycans, glycoproteins, and glycolipids
  • Extend outside cell membrane
  • Form sticky “sugar coat” (glycocalyx)
  • Functions of the glycocalyx
  • Lubrication and Protection
  • Anchoring and Locomotion
  • Specificity in Binding (receptors)
  • Recognition (immune response)
  • Figure 3-2 The Plasma MembraneEXTRACELLULAR FLUIDPhospholipidbilayerIntegral proteinwith channelIntegralglycoproteinsGlycolipidsof glycocalyxHydrophobictailsPlasmamembraneCholesterolHydrophilicheadsPeripheralproteinsGatedchannelCytoskeleton(Microfilaments) 2 nmCYTOPLASM3-2 Organelles and the Cytoplasm
  • Cytoplasm
  • All materials inside the cell and outside the nucleus
  • Cytosol (intracellular fluid)
  • Dissolved materials
  • Nutrients, ions, proteins, and waste products
  • High potassium/low sodium
  • High protein
  • High carbohydrate/low amino acid and fat
  • Organelles
  • Structures with specific functions
  • 3-2 Organelles and the Cytoplasm
  • The Organelles
  • Nonmembranous organelles
  • No membrane
  • Direct contact with cytosol
  • Include the cytoskeleton, microvilli, centrioles, cilia, ribosomes, and proteasomes
  • Membranous organelles
  • Covered with plasma membrane
  • Isolated from cytosol
  • Include the endoplasmic reticulum (ER), the Golgi apparatus, lysosomes, peroxisomes, and mitochondria
  • 3-2 Organelles and the CytoplasmNonmembranous OrganellesSix types of nonmembranous organellesCytoskeleton Microvilli Centrioles Cilia Ribosomes Proteasomes3-2 Organelles and the Cytoplasm
  • The Cytoskeleton
  • Structural proteins for shape and strength
  • Microfilaments
  • Intermediate filaments
  • Microtubules
  • 3-2 Organelles and the Cytoplasm
  • The Cytoskeleton
  • Microfilaments — thin filaments composed of the protein actin
  • Provide additional mechanical strength
  • Interact with proteins for consistency
  • Pair with thick filaments of myosin for muscle movement
  • 3-2 Organelles and the Cytoplasm
  • The Cytoskeleton
  • Intermediate filaments — mid-sized between microfilaments and thick filaments
  • Durable (collagen)
  • Strengthen cell and maintain shape
  • Stabilize organelles
  • Stabilize cell position
  • 3-2 Organelles and the Cytoplasm
  • The Cytoskeleton
  • Microtubules — large, hollow tubes of tubulin protein
  • Attach to centrosome
  • Strengthen cell and anchor organelles
  • Change cell shape
  • Move vesicles within cell (kinesin and dynein)
  • Form spindle apparatus
  • 3-2 Organelles and the Cytoplasm
  • The Cytoskeleton
  • Thick filaments
  • Myosin protein in muscle cells
  • Figure 3-3a The CytoskeletonMicrovillusMicrofilamentsPlasma membraneTerminal webMitochondrionIntermediatefilamentsEndoplasmicreticulumMicrotubuleSecretoryvesicleThe cytoskeleton provides strength andstructural support for the cell and its organelles. Interactions between cytoskeletal components are also important in moving organelles and in changing the shape of the cell.Figure 3-3b The CytoskeletonMicrovillusMicrofilamentsTerminal webThe microfilaments andmicrovilli of an intestinal cell.Such an image, produced by a scanning electron microscope, is called a scanning electron micrograph (SEM) (SEM  30,000).Figure 3-3c The CytoskeletonMicrotubules (yellow) in a living cell, as seen afterspecial fluorescent labeling(LM  3200).3-2 Organelles and the Cytoplasm
  • Microvilli
  • Increase surface area for absorption
  • Attach to cytoskeleton
  • Centrioles in the Centrosome
  • Centrioles form spindle apparatus during cell division
  • Centrosome cytoplasm surrounding centriole
  • Cilia
  • Small hair-like extensions
  • Cilia move fluids across the cell surface
  • Figure 3-4a Centrioles and CiliaMicrotubulesCentriole. A centriole consistsof nine microtubule triplets(known as a 9  0 array). A pairof centrioles orientated at rightangles to one another occupiesthe centrosome. Thismicrograph, produced by a transmission electronmicroscope, is called a TEM.Figure 3-4b Centrioles and CiliaPlasma membraneMicrotubulesBasal bodyCilium. A cilium contains nine pairs ofmicrotubules surrounding a central pair(9  2 array). The basal body to which the cilium is anchored has a structure similar to that of a centriole.Figure 3-4c Centrioles and CiliaReturn strokePower strokeCiliary movement. Action of a single cilium. During the power stroke, the cilium isrelatively stiff; during the return stroke, itbends and returns to its original position.3-2 Organelles and the Cytoplasm
  • Ribosomes
  • Build polypeptides in protein synthesis
  • Two types
  • Free ribosomes in cytoplasm
  • Manufacture proteins for cell
  • Fixed ribosomes attached to ER
  • Manufacture proteins for secretion
  • Proteasomes
  • Contain enzymes (proteases)
  • Disassemble damaged proteins for recycling
  • 3-2 Organelles and the Cytoplasm
  • Membranous Organelles
  • Five types of membranous organelles
  • Endoplasmic reticulum (ER)
  • Golgi apparatus
  • Lysosomes
  • Peroxisomes
  • Mitochondria
  • 3-2 Organelles and the Cytoplasm
  • Endoplasmic Reticulum (ER)
  • Endo- = within, plasm = cytoplasm, reticulum = network
  • Cisternae are storage chambers within membranes
  • Functions
  • Synthesis of proteins, carbohydrates, and lipids
  • Storage of synthesized molecules and materials
  • Transport of materials within the ER
  • Detoxification of drugs or toxins
  • 3-2 Organelles and the Cytoplasm
  • Endoplasmic Reticulum (ER)
  • Smooth endoplasmic reticulum (SER)
  • No ribosomes attached
  • Synthesizes lipids and carbohydrates
  • Phospholipids and cholesterol (membranes)
  • Steroid hormones (reproductive system)
  • Glycerides (storage in liver and fat cells)
  • Glycogen (storage in muscles)
  • 3-2 Organelles and the Cytoplasm
  • Endoplasmic Reticulum (ER)
  • Rough endoplasmic reticulum (RER)
  • Surface covered with ribosomes
  • Active in protein and glycoprotein synthesis
  • Folds polypeptide protein structures
  • Encloses products in transport vesicles
  • Figure 3-5a The Endoplasmic ReticulumNucleusRough endoplasmicreticulum with fixed(attached) ribosomesSmoothendoplasmicreticulumRibosomesThe three-dimensional relationships between the rough and smooth endoplasmic reticula are shown here.CisternaeFigure 3-5b The Endoplasmic ReticulumRough endoplasmicreticulum with fixed(attached) ribosomesFreeribosomesSmoothendoplasmicreticulumTEM  111,000EndoplasmicReticulumRough endoplasmicreticulum and freeribosomes in thecytoplasm of a cell.3-2 Organelles and the Cytoplasm
  • Golgi Apparatus
  • Vesicles enter forming face and exit maturing face
  • Functions
  • Modifies and packages secretions
  • Hormones or enzymes
  • Released through exocytosis
  • Renews or modifies the plasma membrane
  • Packages special enzymes within vesicles for use in the cytoplasm
  • Figure 3-6a The Golgi ApparatusSecretoryvesiclesSecretoryproductTransportvesiclesHere is a three-dimensionalview of the Golgi apparatuswith a cut edge.Figure 3-6b The Golgi ApparatusGolgi apparatusTEM  42,000This is a sectional view of the Golgiapparatus of an active secretory cell.Figure 3-7 Protein SynthesisProtein releasedinto cytoplasmSmooth ERRibosomeDNARough ERmRNACytoplasmNucleusTransportvesicleNuclearporeFigure 3-7 Protein SynthesisCisternaeLysosomeExocytosis atcell surfaceSecretingvesicleCis faceof GolgicomplexTrans faceof GolgicomplexMembranerenewalvesicleMembranerenewalFigure 3-7 Protein SynthesisDNAmRNACytoplasmNucleusFigure 3-7 Protein SynthesisRibosomeRough ERmRNACytoplasmFigure 3-7 Protein SynthesisProtein releasedinto cytoplasmRibosomeFigure 3-7 Protein SynthesisRough ER CytoplasmFigure 3-7 Protein SynthesisSmooth ERTransportvesicleFigure 3-7 Protein SynthesisCisternaeCis faceof GolgicomplexFigure 3-7 Protein SynthesisCisternaeCis faceof GolgicomplexTrans faceof GolgicomplexFigure 3-7 Protein SynthesisLysosomeTrans faceof GolgicomplexFigure 3-7 Protein SynthesisExocytosis atcell surfaceSecretingvesicleTrans faceof GolgicomplexMembranerenewalvesicleMembranerenewal3-2 Organelles and the Cytoplasm
  • Lysosomes
  • Powerful enzyme-containing vesicles
  • Lyso- = dissolve, soma = body
  • Primary lysosome
  • Formed by Golgi apparatus and inactive enzymes
  • Secondary lysosome
  • Lysosome fused with damaged organelle
  • Digestive enzymes activated
  • Toxic chemicals isolated
  • 3-2 Organelles and the Cytoplasm
  • Lysosomes
  • Functions
  • Clean up inside cells
  • Autolysis
  • 3-2 Organelles and the CytoplasmClean Up inside CellsBreak down large moleculesAttack bacteriaRecycle damaged organellesEject wastes by exocytosis3-2 Organelles and the Cytoplasm
  • Autolysis
  • Auto- = self, lysis = break
  • Self-destruction of damaged cells
  • Lysosome membranes break down
  • Digestive enzymes released
  • Cell decomposes
  • Cellular materials recycle
  • Figure 3-8 Lysosome FunctionsActivation of lysosomesoccurs when:GolgiapparatusA primary lysosome fuses withthe membrane of anotherorganelle, such as a mitochondrionDamaged organelleAutolysis liberatesdigestive enzymesSecondarylysosomePrimary lysosomeA primary lysosome fuses withan endosome containing fluidor solid materials from outsidethe cellReabsorptionReabsorptionEndosomeThe lysosomal membranebreaks down during autolysisfollowing injury to, or death of,the cellSecondarylysosomeExtracellularsolid or fluidEndocytosisExocytosisejects residueExocytosisejects residue3-2 Organelles and the Cytoplasm
  • Peroxisomes
  • Are enzyme-containing vesicles
  • Break down fatty acids, organic compounds
  • Produce hydrogen peroxide (H2O2)
  • Replicate by division
  • 3-2 Organelles and the Cytoplasm
  • Membrane Flow
  • A continuous exchange of membrane parts by vesicles
  • All membranous organelles (except mitochondria)
  • Allows adaptation and change
  • 3-2 Organelles and the Cytoplasm
  • Mitochondria
  • Have smooth outer membrane and inner membrane with numerous folds (cristae)
  • Matrix
  • Fluid around cristae
  • Mitochondrion takes chemical energy from food (glucose)
  • Produces energy molecule ATP
  • 3-2 Organelles and the Cytoplasm
  • Mitochondrial Energy Production
  • Glycolysis
  • Glucose to pyruvic acid (in cytosol)
  • Citric acid cycle (also known as the Krebs cycle and the tricarboxylic acid cycle or TCA cycle)
  • Pyruvic acid to CO2 (in matrix)
  • Electron transport chain
  • Inner mitochondrial membrane
  • 3-2 Organelles and the CytoplasmMitochondrial Energy ProductionCalled aerobic metabolism (cellular respiration)Mitochondria use oxygen to break down food and produce ATPGlucose + oxygen + ADP  carbon dioxide + water + ATPFigure 3-9a MitochondriaInner membraneOrganic moleculesand O2OutermembraneMatrixCristaeEnzymesCristaeCytoplasm of cellMatrixOutermembraneMitochondrionTEM  46,332Shown here is the three-dimensional organization and acolor-enhanced TEM of a typical mitochondrion in section.Figure 3-9b MitochondriaGlucoseCYTOPLASMGlycolysisPyruvateEnzymesandcoenzymesof cristaeADP phosphateCitric AcidCycleMATRIXMITOCHONDRIONThis is an overview of the role of mitochondria in energy production. Mitochondria absorb short carbon chains (such as pyruvate) and oxygen and generate carbon dioxide and ATP.3-3 Cell Nucleus
  • Nucleus
  • Largest organelle
  • The cell’s control center
  • Nuclear envelope
  • Double membrane around the nucleus
  • Perinuclear space
  • Between the two layers of the nuclear envelope
  • Nuclear pores
  • Communication passages
  • Figure 3-10a The NucleusNucleoplasmChromatinNucleolusNuclear envelopeNuclear poreNucleusTEM  4800Important nuclear structures are shown here.Figure 3-10b The NucleusNuclear porePerinuclear spaceNuclear envelopeA nuclear pore is a largeprotein complex that spansthe nuclear envelope.Figure 3-10c The NucleusNuclear poresInner membrane ofnuclear envelopeBroken edge ofouter membraneOuter membrane ofnuclear envelopeNucleusFreeze fracture SEM  9240This cell was frozen and then broken apart to make itsinternal structures visible. The technique, called freezefracture or freeze-etching, provides a unique perspectiveon the internal organization of cells. The nuclear envelopeand nuclear pores are visible. The fracturing process broke away part of the outer membrane of the nuclear envelope, and the cut edge of the nucleus can be seen.3-3 Cell Nucleus
  • Contents of the Nucleus
  • DNA
  • All information to build and run organisms
  • Nucleoplasm
  • Fluid containing ions, enzymes, nucleotides, and some RNA
  • Nuclearmatrix
  • Support filaments
  • 3-3 Cell Nucleus
  • Contents of the Nucleus
  • Nucleoli
  • Are related to protein production
  • Are made of RNA, enzymes, and histones
  • Synthesize rRNA and ribosomal subunits
  • Nucleosomes
  • DNA coiled around histones
  • 3-3 Cell Nucleus
  • Contents of the Nucleus
  • Chromatin
  • Loosely coiled DNA (cells not dividing)
  • Chromosomes
  • Tightly coiled DNA (cells dividing)
  • Figure 3-11 The Organization of DNA within the NucleusTelomeres of sister chromatidsNucleusKinetochoreCentromereSupercoiledregionCell preparedfor divisionVisiblechromosomeNondividing cellChromatin innucleusDNAdoublehelixNucleosomeHistones3-3 Cell Nucleus
  • Information Storage in the Nucleus
  • DNA
  • Instructions for every protein in the body
  • Gene
  • DNA instructions for one protein
  • Genetic code
  • The chemical language of DNA instructions
  • Sequence of bases (A, T, C, G)
  • Triplet code
  • 3 bases = 1 amino acid
  • 3-4 Protein Synthesis
  • The Role of Gene Activation in Protein Synthesis
  • The nucleus contains chromosomes
  • Chromosomes contain DNA
  • DNA stores genetic instructions for proteins
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