Cells and proteins - 5

Question 1

What is a cytoskeleton?

Answer 1

network of protein fibres

Question 2

what does the cytoskeleton provide for the cell?

Answer 2

gives mechanical support and shape to cell, involved in movement of cellular components

Question 3

what are the three main components of the cytoskeleton?

Answer 3

microtubules, intermediate filaments, actin filaments

Question 4

what are actin filaments?

Answer 4

polymers of soluble globular protein actin

Question 5

what are actin filaments responsible for?

Answer 5

responsible for cellular movements

Question 6

what are intermediate filaments?

Answer 6

formed from fibrous proteins and are two pairs of monomers wrapped around each other

Question 7

what to intermediate filaments give to a cell?

Answer 7

high mechanical strength

Question 8

what are microtubules?

Answer 8

polymers of a dimer made from soluble globular proteins a-tubulin and b-tubulin

Question 9

what do microtubules govern?

Answer 9

location and movement of membrane bound cell parts

Question 10

where do microtubules come from?

Answer 10

the microtubule-organising centre (MTOC)

Question 11

during mitosis, what happens to the microtubules?

Answer 11

disassemble to form spindle fibres

Question 12

what do the spindle fibres control?

Answer 12

controls the movement of chromosomes

Question 13

what ensures cells division apparatus is correctly located?

Answer 13

aster at each centromere

Question 14

what do the spindle fibres attach to?

Answer 14

kinetochore proteins at centromere

Question 15

what is the purpose of the cell cycle?

Answer 15

regulates growth and replacement of genetically identical cells

Question 16

what are the three stages of interphase?

Answer 16

G1, S and G2

Question 17

what happens in G1?

Answer 17

first growth phase - cell makes new proteins and copies of organelles

Question 18

in what stage in interphase does DNA replication occur?

Answer 18

S phase

Question 19

what are the 4 stages of the M phase?

Answer 19

prophase, metaphase, anaphase, telophase

Question 20

what happens in prophase?

Answer 20

• chromosomes condense
• microtubules disassemble
• nuclear membrane disintegrates

Question 21

what to the microtubules disassemble to produce in prophase?

Answer 21

spindle fibres and asters

Question 22

what happens in metaphase?

Answer 22

• spindle fibres move chromosomes

- line up on metaphase plate at equator

Question 23

what happens in anaphase?

Answer 23

spindle fibres pull sister chromatids apart

Question 24

what happens in telophase?

Answer 24

• separated chromosomes pulled by spindle fibres to opposite poles
• forms daughter nuclei
• chromosomes uncoil
• nuclear membrane made

Question 25

what pulls the membrane in cytokinesis?

Answer 25

actin and myosin

Question 26

what are the two phases of the cell cycle?

Answer 26

interphase and M phase

Question 27

what 2 stages occurs in the M phase?

Answer 27

mitosis and cytokinesis

Question 28

what happens when the rate of the cell cycle is uncontrollably reduced?

Answer 28

results in a degenerative disease

Question 29

what happens if there is an uncontrolled increase in the rate of cell cycle?

Answer 29

results in tumour formation

Question 30

in what parts of the cell cycle is progression regulated by checkpoints?

Answer 30

G1, G2 and metaphase

Question 31

what is monitored at the G1 checkpoint?

Answer 31

cell size

Question 32

if the cell fails the checkpoint at G1 what happens?

Answer 32

cell switches to G0 phase

Question 33

what is the G0 phase?

Answer 33

non-dividing state, cyclin proteins not produced

Question 34

what is assessed at the G2 checkpoint?

Answer 34

assesses success of DNA replication

Question 35

what occurs at the M checkpoint?

Answer 35

checks chromosome alignment

Question 36

what is the role of retinoblastoma protein (Rb)?

Answer 36

• transcription factor inhibitor

- involved in production of proteins required for DNA replication in S phase

Question 37

what happens when low levels of CDK activity is detected?

Answer 37

Rb binds to transcription factor E2F which inhibits transcription of genes needed to enter S phase

Question 38

what happens when high levels of D+CDK activity is detected?

Answer 38

Rb is phosphorylated, no longer bind to transcription factors, promotes transcription of genes

Question 39

where is the p53 protein found?

Answer 39

G1 checkpoint

Question 40

what is a p53 protein?

Answer 40

transcription factor that stimulates DNA repair, arrest cell cycle or trigger cell death

Question 41

what is apoptosis?

Answer 41

programmed cell death

Question 42

what is apoptosis triggered by?

Answer 42

triggered by cell-death signals

Question 43

what triggers cell death from outside the cell?

Answer 43

ligands binding to surface receptor protein

Question 44

what happens when a ligand binds to surface receptor protein?

Answer 44

• receptor protein changes conformation of subunits on cytoplasmic side of membrane
• acts as a signal transduction

Question 45

what is activated by a signal transduction during the extrinsic pathway?

Answer 45

activates protein cascade that produces caspases

Question 46

inside the cell, how is apoptosis triggered?

Answer 46

• p53 protein activated

- activates caspase cascade

Question 47

what occurs during a caspase cascade?

Answer 47

involves a series of post-translational modification to proteins in cytoplasm

Question 48

what does a caspase cascade allow in a cell?

Answer 48

for a rapid response to occur

Question 49

what happens when inactive caspases become activated?

Answer 49

each inhibitor caspase activates several executioner caspases which destroys cellular components

Question 50

what engulfs the fragments of cells after apoptosis?

Answer 50

phagocytic white blood cells