MOD Week 1

Question 1

What is the function of cyclins and CDKs?

Answer 1

Control cell cycle

Question 2

What cyclins and CDKs are used at what parts of the cell cycle?
Hint: Think full name

Answer 2

G1-S Cyclin E and CDK2
S-G2 Cyclin A and CDK2
G2-M Cyclin B and CDK1
M-G1 Cyclin D and CDK2

Question 3

Which checkpoint is most commonly altered in cancer cells?

Answer 3

R just after G1

Question 4

Why is R refered to as the point of no return?

Answer 4

Once the cells pass this point they will complete a full cell cycle

Question 5

what mechanism allows apoptosis and DNA repair to take place at checkpoints?

Answer 5

p53

Question 6

Describe how CDKs and cyclins control the cell cycle

Answer 6

Cyclin binds to substrate and activates CDK

CDK causes phosphorylation and chemical modification of that substrate whilst bound to Cyclin

Question 7

How do we classify cells?

Answer 7

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

Question 8

Name some labile cell populations

Answer 8

Surface epithelia, bone marrow

Question 9

Name some stable cell populations

Answer 9

liver hepatocytes, bone osteoblasts

Question 10

Name some permanent cell populations

Answer 10

brain neurones, cardiac and skeletal muscle

Question 11

Name the 5 cellular adaptations undertaken by a cell

Answer 11

regeneration 
hypertrophy
hyperplasia
atrophy
metaplasia (changing from one cell type to another)

Question 12

Name some tissues which can undergo regeneration

Answer 12

Liver

CNS can establish different pathways (plasticity)

Question 13

are regenerated cells as good as the original cells?

Answer 13

usually, but not always and not immediately

Question 14

how many times can a cell regenerate?

Answer 14

Depends on longlivity of a cell and the HAYFLICK constant. In humans this is 61.3

Question 15

What is reconstitution. what are some examples?

Answer 15

Replacement of part of the body

Deer antlers, lizards tail

Question 16

Define reconsistution and give some examples

Answer 16

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

Question 17

Give some examples of hyperplasia

Answer 17

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

Question 18

What cell type does hypertrophy most commonly occur in and why?

Answer 18

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

Question 19

Give examples of hypertrophy

Answer 19

body building of skeletal muscle
pregnant uterus (uses hyperplasia as well)

Question 20

Give an example of pathological hypertrophy

Answer 20

hypertension or valve problems

Question 21

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

Answer 21

They are allowed time to rest after heavy exertion (e.g. after finishing a race). In hypertension, the heart is never able to rest.

Question 22

Why is childhood obesity such a problem?

Answer 22

Creates adipocytes, which once they are made will never leave and are capable of filling with fat later in life.

Question 23

How is atrophy different to hypertrophy?

Answer 23

Atrophy is shrinkage OR decrease in NUMBER of cells

Hypertrophy is increase in size (hyperplasia does numbers)

Question 24

what is lost in osteoporosis?

Answer 24

bone mass. NOT CALCIUM.

Note: can cause crush fractures of thoracic vertebrae due to loss of mass.

Question 25

Give examples of pathological atrophy?

Answer 25

atrophy of disuse e.g. muscle
denervation atrophy e.g. wasted hand after median nerve damage
inadequate blood supply e.g. peripheral vascular disease
loss of endocrine stimulation e.g. menopause and reproductive organs
senile atrophy from aging e.g. brain, heart
pressure on tissues around an enlarging benign tumour (normally secondary to ischaemia)

Question 26

What disease causes cerebral atrophy?

Answer 26

Alzheimer’s

Question 27

Why may cells undergo metaplasia?

Answer 27

Cells are stressed and change into cells which can cope more easily with this stress. The change is reversible.

Question 28

Give 2 examples of metaplasia

Answer 28

Smokers- pseudostratified ciliated brochial epithelium metaplases to stratified squamous epithelium due to effect of cigarette smoke causing stress

Barrett’s oesophagus- stratified squamous epithelium metaplases to gastric glandular epithelium with persistent acid reflux

Question 29

What danger is associated with metaplasia?

Answer 29

That the tissue becomes dysplastic and malignant

Question 30

Why is most commonly affected in metaplasia and why?

Answer 30

Epithelia as most susceptible to irritants as they cover other structures to form physical barrier.

Question 31

What is HYPOplasia?

Answer 31

NOT THE OPPOSITE OF HYPER

CONGENITAL CONDITION of underdevelopment of a tissue or organ at embryonic stage due to an inadequate number of cells. It is on a spectrum with aplasia (which is complete inability for an organ to develop or function normally).

Question 32

Describe aplasia

Answer 32

Complete failure of a specific tissue or organ to develop in embryonic development

e.g. Thymic aplasia resulting from infection and auto-immune problems, aplasia of the kidney

Can also be used to describe an organ whose cells have ceased to proliferate e.g. aplasia of bone marrow in aplastic anaemia

Question 33

Define atresia

Answer 33

Not forming an opening e.g. anus/vagina

Question 34

Define dysplasia

Answer 34

Proliferation of abnormal cells within a tissue which are precancerous, causing enlargement of that tissue.