Unit 1 Part 4c (Hydrophilic Signals And Transduction)

Question 1

What do hydrophilic signalling molecules do?

Answer 1

Bind to transmembrane receptors and do not enter the cytosol

Question 2

Give examples of hydrophilic signalling molecules

Answer 2

Peptide hormones and neurotransmitters

Question 3

Describe signal transduction

Answer 3

Transmembrane receptors change conformation 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.
Transduced hydrophilic signals often involve G proteins or cascades of phosphorylation by kinase enzymes

Question 4

What do G proteins do?

Answer 4

Relay signals from activated receptors to target proteins such as enzymes and ion channels

Question 5

What do phosphorylation cascades involve?

Answer 5

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 6

Describe the recruitment of GLUT4

Answer 6

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

Question 7

What causes diabetes mellitus?

Answer 7

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

Question 8

Describe type 2 diabetes

Answer 8

Generally associated with obesity
Exercise triggers recruitment of GLUT4 so can improve uptake of glucose to fat and muscle cells in subjects with type 2.