Endocrine Pancreas

Question 1

Name the 2 hormones secreted

Answer 1

Insulin

Glucagon

Question 2

What type of hormone is insulin?

Answer 2

Polypeptide

Question 3

Describe the structure of insulin

Answer 3

Polypeptide hormone with 2chains (1A+1B) linked covalently by disulphide bridges and there is also a 3rd disulphide bridge in the A chain

Question 4

What is insulin synthesised as?

Answer 4

Pre-proinsulin

Question 5

What happens to Pre-proinsulin ?

Answer 5

Enters cisternal space of ER
Signal (Pre) peptide is removed
Proinsulin then folds to ensure there s correct alignment of cysteine residues and correct disulphide bonds are formed
Packaged into vesicles
Proteolysis occurs removing the connecting peptide, removing 4aas and breaking the chain in 2.
2chains are then held by disulphide bridges= MATURE INSULIN!!!!!

Question 6

Does insulin have anabolic or catabolic actions?

Answer 6

Anabolic

Question 7

Describe the structure of glucagon

Answer 7

Single chain polypeptide hormone lacking disulphide bridges so has a flexible 3D structure. Takes up active conformation on binding to receptors on target cells!

Question 8

What is it synthesised as?

Answer 8

Pre-proglucagon

Question 9

Catabolic or anabolic actions?

Answer 9

Catabolic

Question 10

What happens once it’s bound to a receptor on the cell surface?

Answer 10

Binding to the receptor activates adenyl cyclase
This increases cAMP intercellularly
High levels of cAMP activate the protein kinase A which phosphorylates
Therefore it activates a number of important enzymes within the cell

Question 11

Rate of secretion of glucagon depends on

Answer 11

Blood glucose concentration