Signalling

Question 1

Explain why medical students might want to learn about signalling?

Answer 1

Understand how cellular process are regulated.
Understand how embryonic development is coordinated
Explain how faulty signalling causes disease

Question 2

What is an endocrine signal?

Give an example of one.

Answer 2

Signal that travels long distance (via blood)

Oestrogen

Question 3

What is a paracrine signal?

Give an example of one.

Answer 3

Signal acts locally I.e on neighbouring cells

Epidermal GF

Question 4

What is an autocrine signal?

Give an example of one.

Answer 4

Acts on the same cell

Insulin-like growth factor 1

Question 5

What is an intracrine signal?

Give an example of one.

Answer 5

Signal produced within cell then acts on nuclear or internalised receptor

Fibroblast growth factor 11

Question 6

What is a juxtacrine signal?

Give an example of one.

Answer 6

Signal on surface of cell directly in contact with receptor on surface of another cell.

Notch

Question 7

Give an example of a type of signal that is hydrophobic.

Answer 7

Steroid hormone i.e testosterone and oestrogen

Question 8

Give an example of some signal types which are hydrophilic.

Answer 8

Peptide hormones - insulin, growth hormone
Peptide growth factors
- EPO
Neurotransmitters - ACh

Question 9

Describe the mechanism of action of a steroid hormone.

Answer 9

Crosses plasma membrane

Binds to internal receptor

Hormone-receptor complex acts as a transcription factor

Directly affects gene transcription

Question 10

By what mechanism do hydrophilic signals relay their message?

Answer 10

Signal transduction

Question 11

With regards to hydrophilic signalling, what is a first messenger?

Answer 11

Extracellular ligand

Question 12

With regards to hydrophilic signalling, what is a secondary messenger?

Answer 12

Intracellular molecule

Question 13

What are the three main types of receptors that respond to a hydrophilic signal?

Answer 13

Ion-channel linked receptors

Enzyme linked receptors

G-protein linked receptors

Question 14

What are the 3 stages of signalling?

Answer 14

Reception
Transduction
Response

Question 15

How do G protein coupled receptors work?

Answer 15

Ligand binds to extracellular domain, causes conformational change in cytoplasmic domain, conformational change allows G protein to bind and be activated (bound to GTP), activated G protein activates downstream enzymes

Question 16

Name 3 main G protein- alpha subunit effectors.

Answer 16

Adenylyl cyclase - makes cyclic AMP

Phosphlipidase C- makes IP3 + DAG which releases calcium

RhoGEFs

Question 17

What is the action of cAMP?

Answer 17

Activates protein kinase A

Activated PKA phosphorylates many downstream target proteins

Question 18

What do second messengers do?

Answer 18

Activate/inhibit many different target proteins

Question 19

Where are alpha-1, alpha-2, beta-1 and beta-2 adrenergic receptors located?

Answer 19

Alpha-1&2 - vascular smooth muscle

Beta-1 - cardiac muscle

Beta-2 - airway smooth muscle

Question 20

Give examples of RTKs.

Answer 20

EGF, FGF, insulin

Question 21

How to receptor tyrosine kinases work?

Answer 21

Ligand binds to extracellular receptor
Receptor dimerises
Cytoplasmic domains have tyrosine kinase activity
Allows cross phosphorylation
Phosphorylated receptor acts as docking site for intracellular signalling proteins
Downstream signalling activated

Question 22

Give an example of a drug which targets a receptor tyrosine kinase.

Answer 22

Drug: Herceptin
Target: HER2 (human EGFR2)
Drug type: antibody
Treats: HER2 positive-breast cancer

Question 23

How does acetyl choline work at the NMJ?

Answer 23

ACh released from motor neurone
ACh binds to receptor on muscle cell and channel opens
Na+ ions enter, cause an action potential
Action potential causes muscle contraction
Acetylcholinesterase enzyme switch off signal

Question 24

How to drugs for myasthenia gravis improve muscle strength?

Answer 24

AChE inhibitors inhibit acetylcholineesterase, enhancing neuromuscular transmission