Cell Cycle and Communication

Question 1

Phases of the cell cycle

Answer 1

G1
S
G2
M

Question 2

G1

Answer 2

Growth phase 1
Cell is metabolically active
Organelles and centrosomes are replicated
DNA and nucleus are NOT replicated

Question 3

S

Answer 3

Synthesis (of DNA)
DNA strands separate by breaking of hydrogen bonds
New strands of DNA synthesised opposite old strands

Question 4

G2

Answer 4

Growth phase 2
Prepares for mitotic phase
Centrosome replication is completed

Question 5

M

Answer 5

Mitosis
Nuclear membrane is dismantled
2 copies of DNA separate from each other
2 nuclei formed each containing 1 copy of DNA

Question 6

Phases of mitosis

Answer 6

Interphase
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis

Question 7

Interphase

Answer 7

G1, S, G2
Chromosomes replicate, each containing 2 sister chromatids
Centrosomes containing centrioles have finished replication

Question 8

Prophase

Answer 8

Chromatin condenses into chromosomes
Copies are held together by centromeres
Microtubules extend from centrosomes towards the mitotic spindle

Question 9

Prometaphase

Answer 9

Nucleolus disappears
Nuclear envelope breaks down
Spindle fibres attach to kinetochores at centromere of sister chromatids

Question 10

Metaphase

Answer 10

Kinetochore microtubules of mitotic spindle align centromeres along the metaphase plate

Question 11

Anaphase

Answer 11

Centromeres split

Microtubules drag each chromatid away from metaphase plate towards centrosome at each end of cell

Question 12

Telophase

Answer 12

Chromosomes revert to chromatin
Nuclear envelope and nucleolus reform
Mitotic spindle breaks down

Question 13

Cytokinesis

Answer 13

Cytoplasm division

Actin-myosin run causes plasma membrane to pinch inwards and separate into two distinct cells

Question 14

Cell cycle checkpoints

Answer 14

G1: Allows to pass if the cell is of adequate size, has sufficient nutrients and undamaged DNA
G2: Allows to pass if the cell has correctly replicated chromosomes, undamaged DNA and an activated MPF
M: Allows to pass if the cell has all chromosomes attached to the spindle apparatus

Question 15

MPF

Answer 15

Mitotic promotion factor
Induces mitosis in eukaryotes
M phase cytoplasm contains regulatory molecule that induces M phase in interphase cells
CDK/cyclin complex

Question 16

CDK

Answer 16

Cyclin dependent kinase
Catalyses phosphorylation of target protein using ATP
Constant concentration
Active only when bound to cyclin subunit

Question 17

Cyclin

Answer 17

Regulatory molecule that binds CDK

Concentration varies throughout the cell cycle to maintain appropriate mitosis levels

Question 18

Cyclin/CDK mechanism

Answer 18

M-cyclin binds inactive CDK1 molecule
M-CDK complex formed but is inactive
CDK-activating kinase (CAK) adds an activating phosphate to the CDK molecule
Wee1 adds an inhibitory phosphate to the CDK molecule
To be active, CDK must have ONE phosphate so the inhibitory phosphate is removed by CDC25

Question 19

4 effects of MPF

Answer 19

Phosphorylate chrmosomal proteins to initiate M
Phosphorylate lamins to initiate nuclear envelope breakdown
Phosphorylate microtubule associated proteins to activate mitotic spindle
Phosphorylate cyclin degradation enzyme to decrease cyclin concentration

Question 20

5 targets of MPF

Answer 20

Condensins
Microtubule associated proteins
Lamins
Histones
Golgi matrix

Question 21

APC disassembly

Answer 21

Anaphase promoting complex
APC polyubiquitinates cyclin to mark it for degradation in a negative feedback loop
Concentration of cyclin/CDK complex increases and this heterodimer promotes APC to polyubiquitinate cyclin

Question 22

Proto-oncogene

Answer 22

Gene that produces a protein that promotes progress through the cell cycle
Functions normally
Expressed for a short time at a specific point in the cell cycle then degraded

Question 23

Oncogene

Answer 23

Gene that produces at protein such as RAS that promotes progress through the cell cycle but functions abnormally
Expressed at inappropriate time or for too long

Question 24

4 pathways activated by RAS

Answer 24

RAF
PI3K
RALGDS
PLC

Question 25

RAF pathway

Answer 25

Phospholipase A Cell cycle progression Transcription

Question 26

PI3K pathway

Answer 26

``` Inhibition of GSK3 Protein Kinase C Survival Transcription Cytoskeletal signals Translation ```

Question 27

RALGDS pathway

Answer 27

Phospholipase D Transcription Vesicle trasnport Cell cycle progression

Question 28

PLC pathway

Answer 28

Protein Kinase C | Calcium signalling

Question 29

3 types of oncogene mutation

Answer 29

Point - hyperactive growth stimulating protein Duplication - normal growth stimulating protein in excess Translocation - normal growth stimulating protein in excess

Question 30

4 stages of cell-cell communication

Answer 30

Signal reception Signal processing Signal response Signal deactivation

Question 31

Signal reception

Answer 31

Intracellular signals bind specific receptors | Binding of signal to protein causes conformational change indicating signal has been received

Question 32

Intracellular signal

Answer 32

Typically hormones, always a small molecule

Question 33

Steroid hormones

Answer 33

Direct effect Bind to cytosolic receptors Transported to nucleus to alter gene expression

Question 34

Small, hydrophobic primary messengers bind to...

Answer 34

Cytosolic and nuclear receptors

Question 35

Large, hydrophilic primary messengers bind to...

Answer 35

Membrane and cell surface receptors

Question 36

Signal processing

Answer 36

G proteins are activated by GTP binding GTP binding triggers rapid production of large quantities of secondary messengers to amplify original signal These diffuse rapidly and spread hormone throughout the cell

Question 37

Signal transduction

Answer 37

A type of signal processing where the intracellular secondary messenger links activated enzyme with signalling cascade

Question 38

G proteins

Answer 38

Intracellular peripheral membrane proteins activated by GTP binding

Question 39

RTKs

Answer 39

Transmembrane proteins that bind a hormone signal at tyrosine site Phosphorylate each other to carry out cellular processes

Question 40

IP3 gated calcium channels

Answer 40

``` IP3 activated by G protein bound to GTP Phospholipase C activated PIP2 activated IP3 activated IP3 binds calcium pump which causes it to open Calcium is released into the cytosol ```

Question 41

Regulation of calcium pump

Answer 41

Calcium becomes own negative feedback loop initiator by binding to the IP3 gated calcium pump. When enough calcium is bound to the pump the IP3 dissociates and the channel closes

Question 42

Signal response

Answer 42

Gene expression Protein activity Metabolism