(L4) The cell cycle and Apoptosis

?
What happens at metaphase?
Chromosomes are lined up at the metaphase plate
1 of 17
What holds the chromatids before anaphase?
Cohesin protein complex
2 of 17
What happens at anaphase?
Sister chromatids separate as separase protease cleaves a subunit of cohesin
3 of 17
How is separase activated?
Before anaphase, securin protein inhibits separase, during mitosis, M-Cdk activates anaphase-promoting complex by promoting binding of Cdc20 protein (APC is a ubiquitin ligase), APC ubiquinates securin, releasing activated separase
4 of 17
Describe the exit from mitosis
APC adds ubiquitin to M-cyclin, M-cyclin is destroyed, APC is inactivated in the absence of M-cyclin
5 of 17
What is apoptosis?
Programmed cell death
6 of 17
Give some examples of apoptosis
Tadpole tails, between didgets, death of cells with excessive DNA, death of cells affected by various kinds of cellular stress
7 of 17
How is it distinct from necrosis?
Rapid accidental death of cells, apoptosis is much more structured
8 of 17
Briefly describe the processes of apoptosis
Cell shrinks, plasma membrane forms blebs, cytoskeleton collapses, nuclear envelope dissembles, nuclear DNA is broken into fragments, leads to DNA laddering, cell surface is altered, leading to phagocytosis by a neighbouring cell
9 of 17
What does apoptosis involve the action of?
Proteases and DNases (Enzymes involved in breaking down proteins &DNA)
10 of 17
What is the principle mechanism of apoptosis?
Capases (proteases with cystine at active site and cleave targets at aspartic acid residues)
11 of 17
What are capases synthesised as?
Inactive precursors (Procapases)
12 of 17
Why are capases synthesised as procapases?
They can't be active in the cell when the cell does not need to undergo apoptosis
13 of 17
How are the procapases activated into capases?
By the removal of the prodomain and cleavage of the remaining polypeptide into large and small subunits
14 of 17
Cells contain multiple types of capsases, name the type types
1) Initiator caspases activate procapases (they have extra long prodomains through which they associate with adaptor proteins to form activation complexes), 2) Effector capases break down target proteins
15 of 17
Name 2 examples of target proteins that an effector capases breaks down
Lamin (nuclear lamina protein) and DNase (DNase enzyme needs to be activated and it is activated by the breakdown of an inhibitor protein)
16 of 17
How many procaspase molecules can be cleaved by one initiator caspase molecule
Many procaspases can be cleaved by a single initiator caspase molecule in what is called a caspase cascade
17 of 17

Other cards in this set

Card 2

Front

What holds the chromatids before anaphase?

Back

Cohesin protein complex

Card 3

Front

What happens at anaphase?

Back

Preview of the front of card 3

Card 4

Front

How is separase activated?

Back

Preview of the front of card 4

Card 5

Front

Describe the exit from mitosis

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

Cancer
See all Biology resources »See all Cellular Biochemistry resources »