Cell Cycle Part 1

Interphase

The phase of the cell cycle in which the cell prepares for mitosis. It consists of three subphases: G1, S, and G2.

G1 phase

The first phase of interphase where the cell grows, carries out normal functions, and prepares for DNA replication. (Organelles duplicate)

S phase

The phase during interphase when DNA is replicated.

G2 phase

The phase following S phase where the cell continues to grow and prepares for mitosis.

Chromosome condensation

The process by which chromosomes become more compact and visible during prophase of mitosis.

MPF/Maturation promoting factor

A complex of cyclin and cyclin-dependent kinase (CDK) that triggers the transition from G2 to M phase in the cell cycle.

Cyclin

Regulatory proteins that bind to CDKs to activate them, driving the progression of the cell cycle.

CDK/cyclin dependent kinase

Enzymes that, when bound to cyclins, drive cell cycle progression by phosphorylating

CDK regulation

1. Cyclin proteins (synthesis, degradation, localization)

2. Phosphorylation of CDK itself

3. Binding of inhibitors to CDK

Wee1

A kinase that adds inhibitory phosphate to CDK, acting as a negative regulator of cell cycle progression.

CAK

CDK activating kinase that adds an activating phosphate to CDK

Cdc25

A phosphatase that removes inhibitory phosphates from CDKs, activating them and promoting cell cycle progression.

CDK regulation by phosphorylation

1. Cyclin with CDK subunit associate

2. Wee1 inhibits

3. CDK activates

4. Cdc25 removes inhibitor

Phosphorylates Cdc25

Active M-Cdk _________, activating it and creating positive feedback

Inhibits Wee1

Active M-Cdk _________, inhibiting it and creating negative feedback, but still encouraging cell division

Anaphase promoting complex

A complex of proteins that triggers the transition from metaphase to anaphase by targeting cyclins and securin for degradation.

Ubiquitin

A small protein that is attached to other proteins to mark them for degradation by the proteasome.

Ubiquitination

The process of adding ubiquitin to a target protein to signal its degradation.

Ubiquitin ligase

An enzyme that facilitates the attachment of ubiquitin to a target protein.

Proteasome

A protein complex that degrades ubiquitinated proteins, recycling amino acids

Cohesin

A protein complex that holds sister chromatids together during mitosis until they are separated during anaphase.

Securin

A protein that inhibits separase, preventing the premature separation of sister chromatids.

Separase

An enzyme that cleaves cohesin, allowing sister chromatids to separate during anaphase.

Cdc20

A regulatory protein that activates the APC, promoting the degradation of securin

Cdh-1

A protein that regulates the APC during the cell cycle and facilitates the degradation of cyclins at the end of mitosis instead of securin