General Principles of Cell Communication & Intracellular Signalling

Question 1

What is endocrine signalling?

Answer 1

The process by which hormones are released and reach their targets by being released into the bloodstream, reaching targets that can be far from the gland.

Question 2

What is paracrine signalling?

Answer 2

The process by which cells communicate with other nearby cells (without the use of gap junctions) by releasing hormones that travel by diffusion to their targets.

Question 3

What is autocrine signalling?

Answer 3

The process by which a cell releases a hormone that binds to autocrine receptors on the same cell, inducing a response.

Question 4

What are the 4 main receptor types?

Answer 4

1 - Ligand-gated ion channels (ionotropic receptors)

2 - G-protein-coupled receptors (metabotropic receptors)

3 - Kinase-linked receptors

4 - Nuclear receptors

Question 5

What is an example of an antagonist to nicotinic AChRs?

Answer 5

Curare

Question 6

What is an example of an antagonist to muscarinic AChRs?

Answer 6

Atropa Belladonna alkaloids

Question 7

Give 3 examples of where nicotinic AChRs can be found in the nervous system.

Answer 7

• At all autonomic ganglia between pre- and post-ganglionics.
• At parasympathetic postganglionic ganglia.
• At the NMJ.

Question 8

Give 4 examples of effects of stimulation of muscarinic AChRs.

Answer 8

• Bradycardia
• Salivation
• Bronchospasm (narrowing of bronchi)
• Mydriasis

Question 9

Which type of intermolecular interactions must break to open nicotinic AChRs?

Answer 9

Hydrophobic interactions.

Question 10

Which ions move across open nicotinic AChRs? In which direction do they move?

Answer 10

Na+ in

K+ out

Question 11

Which is the largest family of membrane receptors?

Answer 11

G-protein-coupled receptors (~40% drugs on market target these).

Question 12

Name one function that can be carried out by beta gamma subunits of an activated g protein.

Answer 12

Modulation of Ca2+ channels.

Question 13

Name two functions that can be carried out by an alpha subunit of an activated g protein.

Answer 13

Activation of adenylyl cyclase to convert ATP into cAMP.

Activation of phospholipase C.

Question 14

Describe the hormonal regulation pathway of glycogen metabolism.

Answer 14

In the liver:

• cAMP activates protein kinase A
• Protein Kinase A deactivates P-Glycogen synthase
• Protein kinase A converts inactive phosphorylase kinase into inactive glycogen phosphorylase b
• Phosphorylase kinase-P converts inactive glycogen phosphorylase b into active glycogen phosphorylase a
• Active glycogen phosphorylase a converts Glycogen(n) + Pi -> Glycogen(n-1) + Glucose-1-Phosphate

Question 15

What is a Gq subunit?

Answer 15

A type of alpha subunit of a G protein that activates phospholipase C.

Question 16

What is a Gs subunit?

Answer 16

A type of alpha subunit of a G protein subunit that activates the cAMP-dependent pathway by activating adenylyl cyclase.

Question 17

Describe the pathway taken by phospholipase C.

Answer 17

• PLC is converted into DAG and InsP3.
• InsP3 causes Ca2+ release, causing a biological response
• Ca2+ activates protein kinase C, causing a biological response.

Question 18

What is the difference between a kinase and a phosphatase?

Answer 18

A kinase adds phosphate whereas a phosphatase removes phosphate.

Question 19

Define Kd.

Answer 19

Dissociation constant:

The concentration of agonist when the receptors are half-maximally occupied.

Kd = [R][L]/[RL]

Question 20

Define EC50

Answer 20

The concentration of agonist that causes a half-maximal response.

Question 21

Describe the shape of a graph that shows log agonist against fraction of occupancy.

Answer 21

Sigmoid