1.4c Hydrophilic Signals and Transduction

Question 1

What happens to hydrophillic signalling molecules at the cell?

Answer 1

they bind to transmembrane receptors and do not enter the cytosol

Question 2

Give 2 examples of hydrophilic extracellular signalling molecules

Answer 2

• peptide hormones
• neurotransmitters

Question 3

What happens when a hydrophilic signalling molecule binds to a receptor?

Answer 3

• Transmembrane receptors change conformation when the ligands bind to the extracellular face
• The signal molecules 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 behavior of the cell

Question 5

What do transduced hydrophilic signals often involve?

Answer 5

• G-proteins
• Cascades of phosphorylation by kinase enzymes

Question 6

Explain G-proteins

Answer 6

• They relay signals from activated receptors to target proteins
• Such as enzymes and ion channels

Question 7

What do phosphorylation cascades allow?

Answer 7

more than one intracellular signalling pathway to be activated

Question 8

What are activated receptors?

Answer 8

receptors that have bound a signalling molecule

Question 9

What do phosphorylation cascades involve?

Answer 9

• A series of events with one kinase activating the next in the sequence and so on

-They can result in the phosphorylation of many proteins as a result of the original signalling event

Question 10

Describe what happens once insulin binds to its receptor

Answer 10

• Binding of the peptide hormone insulin to its
  receptor results in an intracellular signalling
  cascade
• that triggers recruitment of GLUT4
  glucose transporter proteins to the cell
  membrane of fat and muscle cells

Question 11

Describe what happens once insulin binds to its receptor (In more detail)

Answer 11

• 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 12

What can diabetes mellitus be caused by?

Answer 12

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

Question 13

What is type 2 diabetes generally associated with?

Answer 13

obesity

Question 14

Explain the effect of exercise on GLUT 4 recruitment

Answer 14

• Exercise also triggers recruitment of GLUT4,

-So can improve uptake of glucose to fat and
muscle cells in subjects with type 2