Biochem: Cell Cycle, Programmed Cell Death, And Cancer

Front 1

What cell cycle phase is when the chromosomal DNA is duplicated?

Back 1

S phase

Front 2

What cell cycle phase is when mitosis occurs and the cell divides into two progeny cells?

Back 2

M phase

Front 3

What cell cycle phase is when the cell can go into G0 where it waits?

Back 3

G1 phase

Front 4

What are the four phases of the cell cycle?

Back 4

S phase, M phase, G1 phase, and G2 phase

Front 5

What separates the S and M phases?

Back 5

Two gaps with G1 and G2 phases

Front 6

What term describes when a cell is in the G0 phase and can reenter the cell cycle?

Back 6

quiescent

Front 7

What term describes when a cell is in the G0 phase and cannot reenter the cell cycle?

Back 7

senescent

Front 8

When G1, S, and G2 phases are combined, they are called what?

Back 8

interphase

Front 9

What is the time between cell divisions for fibroblasts?

Back 9

24 hours

Front 10

What is the time between cell divisions for epithelial cells?

Back 10

24 hour

Front 11

What is the time between cell divisions for hepatic cells?

Back 11

every year

Front 12

What is the time between cell divisions for brain cells?

Back 12

never divide

Front 13

What are Cdks?

Back 13

cyclin-dependent kinases

Front 14

How do cdks function?

Back 14

Cdks phosphorylate Ser and Thr to affect changes in the cell cycle

Front 15

What do cdks do?

Back 15

regulate the cell cycle

Front 16

What regulated cdks?

Back 16

other protein kinases, protein phosphatases, cyclin proteins, Cdk inhibitor proteins

Front 17

What is another name for Cdk1?

Back 17

M phase Cdk or M-Cdk

Front 18

What is necessary to initiate and propagate M Phase?

Back 18

M-Cdk

Front 19

What does M-Cdk bind to initiate and propagate M phase?

Back 19

M-phase cyclin protein (M-cyclin)

Front 20

In what cell cycle phase is M-Cdk present?

Back 20

M-Cdk is present during all cell cycle phases, but M-cyclin is only synthesized during the end of G2

Front 21

What inactivates the M-Cdk-M-cyclin complex? How is this inactivation delivered?

Back 21

The g2/Mphase kinase Wee1 inactivates the M-Cdk:M-cyclin complex through phosphorylation at an inhibitory site (Pi).

Front 22

What is the purpose of Wee1?

Back 22

Wee1 knockouts showed that wee1 signal is to stop the cell from cycling if it is too small.

Front 23

What are general kinds of signals that prevent cell cycling?

Back 23

Signals are induced in errors such as incomplete chromatid replication or by DNA damage

Front 24

What causes an inactive M-Cdk:M-cyclin complex to become active?

Back 24

The complex is phosphorylated by M-phase Cdk activating kinase (M-CAK) at an activation site Pa and then dephosphorylated at the inhibitory site (Pi) by M-Cdc25 phosphatase to become active.

Front 25

What stops M-Cdk activity at the end of M phase?

Back 25

M-Cdk activity is stopped by the anaphase promoting complex (APC) which is part of the ubiquitin system. Ubiquitination targets the M-cyclin to proteosomal degredation and the release of inactive M-Cdk

Front 26

What is a protein that binds and sequesters eukaryotic transcription factor 2F that can serve to give stop and go signals which stop the cell cycle when there is a problem with the cell?

Back 26

Rb or retinoblastoma sensitivity protein

Front 27

What is the active state of Rb or retinoblastoma sensitivity protein?

Back 27

unphosphorylated Rb is the active protein which binds and sequesters eukaryotic transcription factor 2F which stops cell cycling in the G1 phase sending the cell to G0

Front 28

What inactivate the Rb protein and what effect does this have?

Back 28

Phosphorylation of Rb leads to inactivation and the releasing of E2F which binds to regulatory elements in genes which increase DNA pol, dihydrofolate reductase, thymidine kinase, and S-phase cyclins

Front 29

What is the effect of absent Rb?

Back 29

The same effect as phosphorylated Rb which is uncontrolled cell cycling (aka cancer)

Front 30

What is activated when strand breaks occur with DNA?

Back 30

DNA-kinases become active when strand breaks occur. Their phosphorylation signal increases the concentration of the protein p53

Front 31

What is p53?

Back 31

p53 is a transcription factor that enhances the gene waf1 (aka cip1). waf1 codes for protein p21 which inhibits G1 Cdks. If G1 Cdks are inhibited, the cannot phosphorylate Rb and the cell cycle can't proceed into S phase

Front 32

What are the two paths of increased p53?

Back 32

Elevated p53 can give the cell time to repair the DNA damage before proceeding into S phase. Alternatively, if the DNA damage is too great to be repaired, the level of p53 increases until a high enough level is reached to initiate cell death (apoptosis).

Front 33

What happens in cancers with p53 mutations?

Back 33

The mutation in p53 allows cells with damaged DNA to propagate

Front 34

What is the type of cell death from infections or trauma that lyses the cell membrane releasing the cell extracellular space triggerin an inflammatory and immunological response?

Back 34

Necrotic cell death

Front 35

What is the type of cell death that causes the cell to fragment intracellular contents and encapsulate them in membranous particles which are engulfed and digested by phagocytotic cells?

Back 35

apoptotic cell death

Front 36

What are the two major pathways that lead to apoptosis?

Back 36

The death receptor pathway (extrinsic pathway) and the mitochondrial pathway (intrinsic pathway)

Front 37

What are the signals from cells necessary for cellular propagation? What is the effect of the withdrawl of these signals?

Back 37

Autocrine and paracrine secreted growth factors are necessary for cellular propagation. Withdrawl of these or cell cycle abnormalities can activate the mitochondrial apoptotic pathway

Front 38

What are the pro-apoptotic proteins involved in the mitochondrial apoptotic pathway?

Back 38

Bak and Bax ( part of the Bcl-2 protein family)

Front 39

What are the anti-apoptotic proteins involved in the mitochondrial apoptotic pathway?

Back 39

The protein Bcl-2 itself and other proteins in the Bcl-2 subfamily

Front 40

How does bak and bax affect the cell through the mitochondrial apoptotic pathway?

Back 40

Bal and bax release cytochrome c from the mitochrondria. Outside the mt cytochrome c binds the apoptotic protease-activating factor 1 (Apaf1) and procaspase 9 to form a complex called an apoptosome.

Front 41

What is the purpose of an apoptosome?

Back 41

The apoptosome activates procaspace 9 to caspase 9. Caspases are cysteine-aspartic acid protease enzymes which cleave proteins.

Front 42

What ligands activate the death receptor pathway?

Back 42

TNF-a or FASL (Fas ligand)

Front 43

What action occurs upon activation of the death receptor?

Back 43

Recruitment of intracellular adapter proteins such as Fas adapter to the death domain. This then recruits the procaspase 8 to form ta death inducing signaling complex or DISC. Pro-caspase 8 is activated to caspase 8 and joins in activating the caspase cascade.

Front 44

What is any properly functioning gene that is involved in cell division, apoptosis, telmoerase activity, andgiogenesis, or metastasis?

Back 44

protooncogene

Front 45

What is any improperly functioning gene that is involved in cell division, apoptosis, telmoerase activity, andgiogenesis, or metastasis?

Back 45

oncogene (associated with cancer initiation or progression)