1-3 Cell Organization / Function

Question 1

Cytosol

Answer 1

Contains metabolic pathways and the cytoskeleton

Question 2

Nucleus

Answer 2

Contains main genome, DNA RNA synth

Question 3

ER

Answer 3

Synthesis of most lipids, sun proteins for distribution to other organelles and PM

Question 4

Golgi

Answer 4

Modification, sorting, packaging of proteins and lipids for secretion or delivery

Question 5

Lysosomes

Answer 5

Intracellular degradation

Question 6

Endosomes

Answer 6

Sorting of endocytosed material

Question 7

Mitochondria

Answer 7

ATP synthesis via oxidative phosphorylation

Question 8

Peroxisomes

Answer 8

Oxidation of toxic molecules

Question 9

Structure of nucleus

Answer 9

Nucleus pore complexes sit in a hole in the membrane and the membrane is continuous around these pores

Continuouss membrane with ER

Chromatin has territories- gene rich inside, gene poor outside

Question 10

Signal sequences/signal patches

Answer 10

Target molecules to correct compartment

Can be intrinsic or one component of molecule

Frequently regulated by PTM, or blocking

Question 11

3 cytoskeleton systems in cells

Answer 11

Microtubules

Intermediate filaments

Actin filaments

Question 12

Intermediate filaments

Answer 12

10nM (except Latin’s 3.5nM)

Connect adjacent epithelial cells into sheets
Resist shear forces, compression, stretch by controlling elasticity of cytoplasm
Anchor organelles and signaling molecules

NON POLAR, rope like bundles

Bendable resistance to stretch: the more you pull the stiffer they get (unique to intermediate)

Question 13

Types of intermediate filaments

Answer 13

Nuclear: lamins

Vimentin-like: vimentin, Desmond, glial fibrillation acidic protein, peripherin

Epithelial: keratin

Atonal: neurofilament protiens

Question 14

Actin microfilaments

Answer 14

Flexible POLARIZED

Form microvilli, contractile bundles, lamellopodia filopodia, contractile rings, adhesion belt between cells in tissues

sarcomeres
Nuclear actin involved in transcription / nuclear export
Help fibroblasts crawl

Question 15

Dynamic assembly/disassembly of actin filaments

Answer 15

Treadmilling

Minus end ACTIN-ADP, ADP-actin low affinity and falls off chain and then ADP dissociates, leaves cycles, ATP enters cycle and binds actin, Actin-ATP can add to plus end of filament to lengthen, P expelled

When actin binds ATP, conform change and the actin molecules can now bind the positive end of filament chain

Question 16

Microtubules

Answer 16

Formed from heterodimers of a and b tubular monomers - alpha betas organize into protofilaments strands with a plus and minus end, protofilaments form together to make 13 strange tube

Form a hollow tube like structure

Microtubules organizing center: centrosome

Mitosis spindle
Centrioles and basal bodies

Question 17

Centrosome

Answer 17

Major microtubules organizing center in cells

Centriole pair surrounded by centrosome matrix with nuclearint sites that attract the negative ends of microtubules and the positive ends all stick outwards

Spontaneous formation

Straight and fragile

Question 18

Dynamic instability

Answer 18

Regulates microtubules assembly

Cannot shrink from minus end because gamma tubular end stabilizes

GTP-tubuliln diners add to growing end of microtubule and addition proceeds faster than GTP hydrolysis by the diners so it grows (if hydrolysis occurs faster than shrinks)

GTP binds B tubulin

Question 19

Microtubule motor proteins

Actin based motor proteins

Answer 19

Microtubule: Kinesins / Dyneins

Processive motors, they walk along the microtubule and move things

Actin: myosin , actin needs to be anchored into PM to allow myosin to haul cargo along OR myosin binds PM an actin and helps cell crawl and PM acts as anchor to a substrate

All work by converting chemical E to mechanochem E

Question 20

Actin in a non-muscle cell

Answer 20

Retraction : driven by actin-myosin sliding

Protrusion: driven by actin polymerization