MOD Week 1 Flashcards
What is the function of cyclins and CDKs?
Control cell cycle
What cyclins and CDKs are used at what parts of the cell cycle?
Hint: Think full name
G1-S Cyclin E and CDK2
S-G2 Cyclin A and CDK2
G2-M Cyclin B and CDK1
M-G1 Cyclin D and CDK2
Which checkpoint is most commonly altered in cancer cells?
R just after G1
Why is R refered to as the point of no return?
Once the cells pass this point they will complete a full cell cycle
what mechanism allows apoptosis and DNA repair to take place at checkpoints?
p53
Describe how CDKs and cyclins control the cell cycle
Cyclin binds to substrate and activates CDK
CDK causes phosphorylation and chemical modification of that substrate whilst bound to Cyclin
How do we classify cells?
dependent on ability to multiply
Labile- stem cells divide persistently to replenish losses
stable- stem cells are usually quiescent, or proliferate very slowly. they can change to proliferate persistently when required (requires protoncogenes to change from G0 to G1)
permanent- stem cells are present but cannot do effective proliferation in response to significant cell loss
Name some labile cell populations
Surface epithelia, bone marrow
Name some stable cell populations
liver hepatocytes, bone osteoblasts
Name some permanent cell populations
brain neurones, cardiac and skeletal muscle
Name the 5 cellular adaptations undertaken by a cell
regeneration hypertrophy hyperplasia atrophy metaplasia (changing from one cell type to another)
Name some tissues which can undergo regeneration
Liver
CNS can establish different pathways (plasticity)
are regenerated cells as good as the original cells?
usually, but not always and not immediately
how many times can a cell regenerate?
Depends on longlivity of a cell and the HAYFLICK constant. In humans this is 61.3
What is reconstitution. what are some examples?
Replacement of part of the body
Deer antlers, lizards tail
Define reconsistution and give some examples
Forming an area of cells again which are all different types.
If the end of a finger is removed before the age of 4 and a half years it will grow back completely
Give some examples of hyperplasia
proliferation of endomedutrium under influence of oestrogen
bone marrow producing erythrocytes in reponse to hypoxia (altitude)
Can also cause pathological results e.g. goitre, eczema of the skin from excessive hyperplasia
What cell type does hypertrophy most commonly occur in and why?
permanent cells because they cannot divide and so this is the only way they can respond to increased demand
It is caused by increased functional demand or hormonal stimulation
Give examples of hypertrophy
body building of skeletal muscle pregnant uterus (uses hyperplasia as well)
Give an example of pathological hypertrophy
hypertension or valve problems
In hypertension, the heart is enlarged and causes bad affects on a human. An athlete will also have an enlarged heart. Why is this not a problem
They are allowed time to rest after heavy exertion (e.g. after finishing a race). In hypertension, the heart is never able to rest.
Why is childhood obesity such a problem?
Creates adipocytes, which once they are made will never leave and are capable of filling with fat later in life.
How is atrophy different to hypertrophy?
Atrophy is shrinkage OR decrease in NUMBER of cells
Hypertrophy is increase in size (hyperplasia does numbers)
what is lost in osteoporosis?
bone mass. NOT CALCIUM.
Note: can cause crush fractures of thoracic vertebrae due to loss of mass.
