KA4: communication and signalling: hydrophilic signals and transduction

Question 1

what do hydrophilic signalling molecules bind to?

what do they not enter?

Answer 1

transmembrane receptors

the cytosol

Question 2

give examples of hydrophilic extracellular signalling molecules

Answer 2

• Peptide hormones
• neurotransmitters

Question 3

describe the role of transmembrane receptors in signal transduction

Answer 3

• they 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

Question 4

what do transmembrane receptors act as?

how do they do this?

Answer 4

signal transducers

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

Question 5

What do transduced hydrophilic signals often involve?

Answer 5

G-proteins or cascades of phosphorylation by kinase enzymes

Question 6

What is the role of G-proteins?

Answer 6

relay signals from activated receptors (receptors that have bound a signalling molecule) to target proteins

e.g. enzymes and ion channels.

Question 7

what is the role of phosphorylation cascades?

Answer 7

involve a series of events with one kinase activating the next in the sequence and so on

Question 8

what do phosphorylation cascades result in?

Answer 8

the phosphorylation of many proteins as a result of the original signalling even

Question 9

what do the phosphorylation cascades allow?

Answer 9

more than one intracellular signalling pathway to be activated

Question 10

describe the effects of the binding of the peptide hormone insulin to its receptor

Answer 10

intracellular signalling cascade => recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells

Question 11

what does binding of insulin to its receptor cause?

Answer 11

a conformational change

Question 12

what does the conformational change regarding binding of insulin to its receptor trigger?

Answer 12

phosphorylation of the receptor

Question 13

what does phosphorylation of the receptor start?

Answer 13

• a phosphorylation cascade inside the cell
• leads to GLUT4 - containing vesicles being transported to the cell

Question 14

describe the cause of type 1 diabetes mellitus

Answer 14

failure to produce insulin

Question 15

describe the cause of type 2 diabetes mellitus

Answer 15

loss of receptor function

Question 16

what is type 2 associated with?

Answer 16

obesity

Question 17

describe the role of exercise in the treatment of type 2 diabetes

Answer 17

Exercise = recruitment of GLUT4, so can improve uptake of glucose to fat and muscle cells in ppl w/ t2