Control of the Eukaryotic Cell Cycle 2

Question 1

What are the 4 major forms of signal transduction in cells?

Answer 1

Endocrine, paracrine, neuronal, contact-dependent

Question 2

What is endocrine signalling?

Answer 2

Occurs when endocrine cells release hormones that act on distant target cells in the body

Question 3

What is paracrine signalling?

Answer 3

It is a form of cell-to-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells

Question 4

What is neuronal signalling?

Answer 4

Neurons send electrochemical signals, and once a neuron has been stimulated by stimuli, it will generate an electric potential that travels down the length of the cell

Question 5

What is contact-dependent signalling?

Answer 5

It is a type of cell/extracellular matrix signalling in multicellular organisms that requires close contact. A membrane ligant (protein, lipid, oligosaccharide) and a membrane protein of two adjacent cells interact

Question 6

What are some biological outcomes?

Answer 6

Death; differentiation; cell cycle progression; cell movement

Question 7

How does a cell in G0 re-enter the cell cycle?

Answer 7

It needs activity of G1-phase cyclin-CDK complexes

Question 8

What do the G1-phase cyclin-CDK complexes do to help a cell re-enter the cell cycle?

Answer 8

Regulate progression through the restriction point and trigger a wave of genetic expression need to support commitment into a new cell cycle, S phase and DNA replication

Question 9

What stimulates G1-phase cyclin-CDK complexes?

Answer 9

Mitogens

Question 10

How do mitogens stimulate G1-phase cyclin-CDK complexes?

Answer 10

Mitogens release the breaks on CDK activity, thereby allowing cell cycle entry and progression

Question 11

How is the Ras-MAPK signal transduction pathway triggered?

Answer 11

Mitogens bind to cell-surface receptors which triggers this pathway

Question 12

What is the Ras-MAPK pathway?

Answer 12

The activation of Ras activates the MAP kinase cascade, which leads to increased expression of several immediate early genes (including the transcription regulatory protein Myc)

Question 13

What is the function of Myc?

Answer 13

Increases transcription of many delayed response genes, including the G1 phase cyclin, Cyclin D

Question 14

What does Cyclin D-Cdk4 activate?

Answer 14

A group of transcription regulatory factors called E2F proteins

Question 15

How are E2F proteins released from their inactive site by Rb proteins?

Answer 15

Phosphorylation of Rb proteins by cyclin D-Cdk 4 releases active E2F proteins

Question 16

What is the main function of Rb proteins?

Answer 16

Inhibit cell cycle progression until a cell is ready to divide

Question 17

What do E2F proteins do once they are activated?

Answer 17

They activate expression of their target genes (G1/S phase cyclins and S phase cyclins)

Question 18

What are 2 of the positive feedback loops?

Answer 18

Activate E2F proteins (phosphorylation of Rb) and active G1/S phase cyclin-CDK and active S phase cyclin-CDK (phosphorylation of p27)

Question 19

What happens if mitogens are not available during G1?

Answer 19

The cells enter G0

Question 20

What happens if mitogens are present during G1?

Answer 20

Mitogens stimulate expression of G1-phase cyclins

Question 21

How does apoptosis occur?

Answer 21

DNA damaged is detected by detector enzymes (ATM ATR, Chk1 Chk2). Protein kinases become catalytically active which phosphorylates p53. Once p53 levels rise, it is able to induce the transcription of inhibitory proteins and these bind to/inhibit cyclin-cdk complexes which leds to cell cycle arrest