Cell Cycle

Question 1

Describe the purpose of the cell cycle control system

Answer 1

It is used to control the sequence and timing of the different parts of the cell cycle

Question 2

Identify where in the cell cycle the three main transition points are

Answer 2

G1 to S phase

G2 to M phase

Metaphase to anaphase

Question 3

G1 to S phase transition period

Answer 3

Confirms environment is favorable for proliferation (replication etc) (if unfavorable cell will delay replication and enter rest G0 stage by the signals from other cells blocking cell proliferation)

Question 4

G2 to M phase transition period

Answer 4

Confirms DNA is undamaged and intact after replication

Question 5

Metaphase to anaphase phase transition period

Answer 5

Ensures spindle fibers are attached to chromosomes before pulling apart

Question 6

List the two compounds animal cells need to transition from G1-S

Answer 6

Animals need sufficient nutrients and specific signal molecules in extra cellular fluid.

Question 7

Define extracellular fluid

Answer 7

The fluid located outside of the cell, composed of plasma, interstitial fluid, etc

Question 8

Explain what G0 entails

Answer 8

This is the stage cells enter when it’s found that the environment in unfavorable for proliferation in the G1-S phase transition point. It is a rest stage where the cell is not dividing or preparing to divide, it’s just sort of waiting for the signal that the environment is favorable

Question 9

List the two ways other cells can influence cell proliferation

Answer 9

Other cells can send signals to either stimulate or block cell proliferation

Question 10

State another name for spindle fibers

Answer 10

Mitotic spindles

Question 11

Differentiate between the two types of machinery in the cell cycle

Answer 11

One manufactures new components of the growing cell

The other moves components to correct locations and isolates them during division

Question 12

What’s the connection between the cell cycle control system and this machinery

Answer 12

The cell cycle control system switches this machinery on and off at appropriate times.

Question 13

Identify the chemistry and activating or deactivating a protein or protein complex

Answer 13

Activating and deactivating proteins and protein complexes happens through phosphorylation and dephosphorylation

Question 14

Define phosphorylation

Answer 14

Adding a phosphate to a compound

Question 15

Define protein kinase

Answer 15

Controls phosphorylation. It’s an enzyme that catalyzes the transfers of PO4 to a different compound (substrate)

Question 16

Define substrate

Answer 16

Regulates the activation of protein kinases. They are proteins that bind kinases to activate them

Question 17

Identify the protein used to regulate protein kinases

Answer 17

Cyclin

Question 18

When are protein kinases activated?

Answer 18

At specific times in the cell cycle

Question 19

State and identify the name of the new complex formed

Answer 19

Cyclin-dependent protein kinases (cdks)

Question 20

List the 4 types of cdks

Answer 20

M-cdk
S-cdk, G1
S-cdk
G1-cdk

Question 21

Function of M-cdk

Answer 21

Triggers entry into M phase (mitosis)

Question 22

Function of S-cdk, G1

Answer 22

Starts the S phase (replication)

Question 23

Function of S-cdk

Answer 23

Starts the S phase (replication)

Question 24

Function of G1-cdk

Answer 24

Moves the cell through G1 (growth)

Question 25

Two ways that the concentration of cyclin is controlled

Answer 25

By transcription and proteolysis

Gradual increase in concentration of cyclin is due to increased transcription of cyclin gene

Abrupt decrease is due to concentrated destruction of protein

Question 26

Cyclin a turn on ___________ even though their concentration levels increase slowly

Answer 26

Abruptly

Question 27

Identify the three places where the cell cycle control system can pause the cell cycle

Answer 27

G1 to S transition

G2 to M transition

End of mitosis

Question 28

G1 to S pause explain

Answer 28

Cdk inhibitors are used to keep cell out of S phase and DNA replication

Question 29

G2 to M pause explain

Answer 29

An inhibitory kinase is used to inactivate the complex

Question 30

End of mitosis pause explain

Answer 30

Inhibits APC (anaphase promoting complex) which tags the complex for destruction (if complex isn’t destroyed, cell doesn’t enter anaphase)

Question 31

What would happen if cyclin cdk complexes aren’t stopped at the end of M phase

Answer 31

The cell goes right back into mitosis with no growth

Question 32

3 systems used to neutralize or block cyclin cdk complexes

Answer 32

Eliminating all existing cyclins

Blocking the formation of new cyclins

Deploying cdk inhibitor proteins

Question 33

Explain process of eliminating all existing cyclins

Answer 33

A ubiquitin chain is added to the cyclin, ubiquitin is recognized by a complex called a proteasome, proteasomes have many proteases in them which chop up the protein that was tagged