a tour of the cell animals & plants chapter five

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