Unit 1 KA5 Flashcards
(a)
What does the cytoskeleton do?
gives mechanical support and shape to cells
(a)
What are microtubules?
- hollow cylinders composed of protein tubulin
- from centrosome
- found in cytoskeleton
- found in all eukaryotic cells
- control movement of membrane bound organelles and chromosomes
(a)
What does cell division require?
remodeling of the cytoskeleton
(a)
What deos the formation and breakdown of microtubules involve
- polymerisation (formation)
- depolymerisation (breakdown)
(a)
Spindle fibres
Microtubules form these
active during cell division
(b)
2 main conponents of the cell cycle
- interphase
- mitotic phase (M)
(b)
What does the interphase involve?
G1, S, G2
(b)
G1
first growth phase in Interphase
(b)
S phase
DNA is replicated
(b)
G2
Second growth phase
(b)
Mitotic phase stages
Mitosis, cytokinesis
(b)
What happens in mitosis
- chromosomal material is seperated by the spindle microtubules
- cytokinesis- cytoplasm is seperated into 2 daughter cells
(b)
What phases are there in Mitosis?
- prophase
- metaphase
- anaphase
- telophase
(b)
Prophase
- DNA condenses into chromosomes each consisting of 2 sister chromatids
- Nuclear membrane breaks down
- Spindle microtubules extend from centrosome (MTOC) by polymerisation
- they attach to chromosomes via their kinetochores in the centromere region
(b)
Metaphase
Chromosomes are aligned at the metaphase plate (equator of the spindle)
(b)
Anaphase
- as spindle microtubules shorten by depolymerisation sister chromatids are separated
- chromosomes are pulled to opposite poles
(b)
Telophase
chromatids decondense and nuclear membrane are formed around them
(c)
How is the progression through the cell cycle is controlled?
By checkpoints
* mechanisms withinthe cell that asses the condition of the cell during the cell cycle
* halt progression to the next phase until certain requirements are met
(c)
Cyclin Proteins
- accumulate diring cell growth
- involved in regulating cell cycle
(c)
How does progression occur in the cell cycle (with the use of cyclins)
- Cyclins combine with and activate cyclin-dependent kinases (CDKs)
- Active cyclin-CDK complexes phosphorylate proteins that regulate progression through the cell cycle
- if sufficient phosphorylation is reached, progression occurs
(c)
Wht happens at the G2 checkpoint?
the following are assessed:
* success of DNA replication
* any damage to DNA
(c)
What does the metaphase checkpoint do?
controls progression from metaphase to anaphase
* progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules
(c)
What may happen if there is an uncontrolled reduction in the rate of the cell cycle?
degenerative disease
How may tumour formation arise?
By an uncontrolled increase in the rate of the cell cycle
(c)
Proto-oncogene
- normally involved in the control of cell growth/ division
- can mutate to form a tumour-promoting oncogene
(d)
Apoptosis
Cell death/ suicide
(d)
What is apoptosis triggered by?
cell death signals (internal/external)
(d)
Example of external death signal
from lymphocytes
(d)
Example of internal death signal
DNA damage
(d)
What triggers a protein cascade within the cytoplasm?
when external death signal molecules bind to a surface receptor protein
(d)
What causes activation of p53 protein?
DNA damage (internal death signal)
(d)
What does both types of death signal result in?
activation of caspases (protein enzyme)
causes destruction of cell
(d)
How does apoptosis help the cell?
essential during development
remove cells no longer required as development progresses/during metamophosis
(d)
When may cells initiate apoptosis?
absense of growth factors !!
