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A Tour of the CellAnimals & Plants
Chapter Five
Cell StudyOLight microscope – up to
0.2 m; magnify well up to 1000x; not enough for many organelles
Cell StudyOElectron microscope – up to
2nm (hundredfold improvement) – uses electron beam
OSpecimens must be “prepared” first
OTwo types
Cell StudyOScanning Electron Microscope
(SEM) – used for surface study – appears 3-D
OCilia in the windpipe of a rabbit
Cell StudyOTransmission Electron
Microscope (TEM) – internal structure of cells
OUses magnets to bend electrons as they pass through
OCells from windpipe of a rabbit
Cellular PreparationOCell fractionation – take cells
apart & separate organelles for study
OUltracentrifuge – 130,000 rpmOBreak cells apart
(homogenization), then separate organelles (differential centrifugation)
Cellular Preparation
Cell TypesOProkaryotic – no nucleus
OBacteria & archaeaODNA in region called the nucleoid
(has no membrane)OHave plasma membrane,
chromosomes, ribosomes, cytosol
Cell Types
Cell TypesOEukaryotic – have membrane-
bound organelles suspended in cytosol, including a definite nucleus (cytosol + organelles = cytoplasm)OEukaryotic = 10-100 mOProkaryotic = 1-10 m
Eukaryotic Cells & Organelles
Eukaryotic Cells & Organelles
Eukaryotic Cells & Organelles
OPlasma MembraneOSelective barrier
Eukaryotic Cells & Organelles
OMembrane of phospholipids, proteins, glycoproteins
Eukaryotic Cells & Organelles
ONucleusOContains most genesOSurrounded by nuclear envelope
– double lipid bilayer membrane with pores
OInner nuclear side lined with nuclear lamina (protein filaments for structure)
Eukaryotic Cells & Organelles
OInside, DNA is as fibrous chromatinOWill condense into chromosomes during division
ONucleolusOInside nucleusORibosomal RNA (rRNA) made here
& assembled to make ribosomes in cytoplasm
Eukaryotic Cells & Organelles
Eukaryotic Cells & OrganellesORibosomes
OTwo subunits made of ribosomal RNA & protein
OProtein synthesisOFree or on ER (structurally identical)
OFree make proteins that function in cytosol
OBound make proteins that are inserted into membranes, for packaging within other organelles, or exported
Eukaryotic Cells & Organelles
Eukaryotic Cells & Organelles
OER (Endoplasmic reticulum)ONetwork of tubules & sacs
– cisternaeOInternal space – cisternal
spaceOTwo types
Eukaryotic Cells & Organelles
Eukaryotic Cells & Organelles
OSmooth ERONo outer ribosomesOSynthesis of lipidsOCarbohydrate metabolism
Eukaryotic Cells & Organelles
ODetoxify drugs & poisons, esp. in liver
OMuscle cells – Smooth ER pumps calcium ions from cytosol to cisternal space – when muscle is stimulated, Ca rushes back over –
triggers muscle contraction
Eukaryotic Cells & Organelles
Eukaryotic Cells & Organelles
ORough EROProduce secretory proteinsOProtein is made, threads
through pore into cisternal space, folds into proper shape
OMost are glycoproteins
Eukaryotic Cells & Organelles
OSecretory proteins leave ER wrapped in membranes of transport vesicles
OVesicles in transit throughout cellORough ER also makes membranes
for endomembrane system(nuclear envelope, ER, Golgi, lysosomes, vacuoles, plasma membrane)
Eukaryotic Cells & Organelles
OGolgi ApparatusOManufacture, store, sort,
ship products of EROFlattened sacs (cisternae)OTwo faces – cis (receive
transport vesicles from ER) and trans (vesicles pinch off to other places)
Products move from cis to trans - modified & refined along the way
Eukaryotic Cells & Organelles
Eukaryotic Cells & Organelles
OLysosomesOHydrolytic enzymes digestionOpH 5OEnzymes made in rough ER, put
through Golgi, then into lysosomesODigest by fusing with food vacuole,
bacteria, invaders
Eukaryotic Cells & Organelles
OAutophagy – recycle own cell’s materials (like old organelles)
O Organismal advantage – removal of webbed hands during embryonic development - tadpole has tail destroyed as it turns into a frog
Eukaryotic Cells & Organelles
OIf lysosomes can’t digest – lack of functioning enzyme – cell gets filled with indigestible materials OTay-Sachs
Eukaryotic Cells & Organelles
Eukaryotic Cells & Organelles
OVacuolesOFood, contractile, centralOCentral vacuole – in plants
OEnclosed by tonoplastOReserves of proteins, inorganic ions, metabolic wastes, pigments, animal warning system
ORole in growth
Eukaryotic Cells & Organelles
OEndomembrane System (organelles that are underlined)
Eukaryotic Cells & Organelles
OMitochondria – cellular respirationOFood ATPOSemiautonomous organelleOTwo layers – each
phospholipid bilayerOOuter membrane - smoothOInner is convoluted – cristae
Eukaryotic Cells & Organelles
OSeparates into two compartmentsOIntermembrane space – between outer and inner membranes
OMitochondrial matrix – insideOContains DNA, enzymes,
ribosomes
Eukaryotic Cells & Organelles
OChloroplastsOSite of photosynthesisOTwo membranesOInside are thylakoids (sacs)
– each is called a granumOFluid outside thylakoid –
stroma (contain DNA, ribosomes, enzymes)
Eukaryotic Cells & Organelles
OPeroxisomesOContain enzymes that
transfer hydrogen to oxygen, making H2O2 (hydrogen peroxide)
OOrganelle helps detoxification, fatty acid hydrolysis
OThen converts H2O2 to H2O
CytoskeletonONetwork of fibersOSupport & shapeOAnchorage for organelles & enzymes
CytoskeletonOCell motilityOInteraction with motor molecules
(proteins)OMovement of cilia & flagella –
cytoskeleton components can slide past each other
OContraction of muscle cellsOOrganelles can move within cell
CytoskeletonOThree
fibers
Cell WallsOProtects, shape, prevents
excessive water uptakeOCellulose embedded in
protein/polysaccharide matrix
OAs young plant, makes primary cell wall
Cell WallsOBetween walls of adjacent cells –
middle lamella (rich in pectins – thick)
OCell stops growing – makes thicker secondary cell wall
Extracellular Matrix (ECM)
OSurface of animal cellsOGlycoproteins (mostly
collagen) embedded in proteoglycan network
Extracellular Matrix (ECM)
OCells attached to ECM by fibronectins (glycoprotein)
Bind to integrins (receptor molecules on plasma membrane)
Attach ECM to plasma membrane to coordinate any changes
OECM can coordinate cell’s behavior
Intercellular JunctionsOPlasmodesmata – perforations in
plant cell wallsOAllows cytosol, water, proteins,
RNA, small solutes to pass betweenOPlasma
membrane lines channel
Intercellular JunctionsO Animal cells:
1. Tight junctions – membranes of neighboring cells are fused – prevent EC fluid leakage
2. Desmosomes (anchoring junctions) – fastens cells into strong sheets like rivets
Intercellular Junctions3. Gap junctions (communicating
junctions) – provides cytoplasmic channel between adjacent cells
O Allows small ions & molecules to pass
O Flow of ions coordinates cell contractions