Unit 1 - Topic 4 - Communication and signalling - Section C - Hydrophilic signals and transduction

Question 1

What do hydrophilic signalling molecules bind to

Answer 1

Transmembrane receptors and do not enter the cytosol

Question 2

What are examples of hydrophilic extracellular signalling molecules

Answer 2

Peptide hormones and neurotransmitters

Question 3

Transmembrane receptors change
conformation when they bind to what and what happens to the signal

Answer 3

When the ligand binds to the extracellular face; the signal molecule does not enter the cell, but the signal is transduced across the plasma membrane

Question 4

How do transmembrane receptors act as signal transducers

Answer 4

By converting the extracellular ligand-binding event into intracellular signals, which alters the behaviour of the cell

Question 5

Transduced hydrophilic signals often involve what

Answer 5

G-proteins or cascades of phosphorylation by kinase enzymes

Question 6

What do G-proteins do

Answer 6

G-proteins relay signals from activated receptors (receptors that have bound a signalling molecule) to target proteins such as enzymes and ion channels.

Question 7

What does phosphorylation cascades allow

Answer 7

More than one intracellular signalling pathway to be activated

Question 8

What is involved in a phosphorylation cascade

Answer 8

A series of events with one kinase activating the next in the sequence and so on. Phosphorylation cascades can result in the phosphorylation of many proteins as a result of the original signalling event

Question 9

What does the binding of the peptide hormone insulin to its receptor results in

Answer 9

An intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells

Question 10

Binding of insulin to its receptor causes what kind of change and what does this trigger

Answer 10

Binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor. This starts a phosphorylation cascade inside the cell, which eventually leads to GLUT4-containing vesicles being transported to the cell membrane.

Question 11

What can diabetes mellitus be caused by

Answer 11

Failure to produce insulin (type 1) or loss of receptor function (type 2)

Question 12

What is type 2 generally associated with

Answer 12

obesity

Question 13

What does exercise trigger

Answer 13

Exercise also triggers recruitment of GLUT4, so can improve uptake of glucose to fat and muscle cells in subjects with type 2