Insulin Secretion and signalling

Question 1

Where is insulin made?

Answer 1

Pancreatic islets

Question 2

What types of cells pancreatic islets and what do they secrete?

Answer 2

beta cells - insulin
alpha cells - glucagon
delta cells - somatostatin
PP cells - pancreatic polypeptide

Question 3

What is the structure of insulin?

Answer 3

2 polypeptidechains
linked by disulfide bonds
connecring (C) peptide

Question 4

How does glucose enter beta cells?

Answer 4

through GLUT2 transporter

Question 5

What happens when glucose enters the beta cell?

Answer 5

Phosphorylated by glucokinase
Increases intracellular ATP
ATP inhibits K ATP channel
Depolarisation
Voltage gated Ca2+ channels open
Vesicles fuse to membrane
Secrete insulin

Question 6

Desribe the two phases of insulin secretion

Answer 6

1st-readily releasable pool

2nd- mobilization

Question 7

What subunits make up the K ATP channel? What inhibits each subunit?

Answer 7

Kir6.2 pore - ATP

SUR1 regulatory - sulphonylurea

Question 8

What stimulates the K ATP channel at the SUR1 subunit?

Answer 8

diazoxide

Question 9

Describe what the defect in MODY

Answer 9

Glucokinase impared
Glucose sensing defect
Increases threshold for insulin secretion

Question 10

What are the three phases of the signalling cascade?

Answer 10

Reception of hormone
Transduction
Cellular response

Question 11

What is the name of the insulin receptor?

Answer 11

Tyrosine kinase

Question 12

Describe the tyrosine kinase receptor

Answer 12

2 alpha subunits
2 beta subunits
disulfide bridges

Question 13

Describe what happens in insulin signalling

Answer 13

Insulin binds to alpha subunits
Autophosphorylation at beta subunits
Insulin receptor substrates phosphorylated
Causes gene expression and glycogen synthesis

Question 14

Describe how glycogen is synthesised

Answer 14

PKB causes GLUT4 to translocate to surface

Glucose into cell

Question 15

What are the biological processes insulin increases?

Answer 15

Glucose uptake
Lipogenesis
Glycogen synthesis

Question 16

What biological processes does insulin prevent?

Answer 16

Lipolysis

Gluconeogenesis in liver

Question 17

What happens in Donohue syndrome (leprachaunism)

Answer 17

insulin resistance
growth abnormlities
elfin features
growth retardation

Question 18

What happens in Robson Mendenhall syndrome?

Answer 18

insulin resistance 
hyperglycaemia 
compensatory hyperinsulinaemia
leads to: hyperpigmentatoin
DKA hypoglycaemia respone

Question 19

Where are ketone bodies produced?

Answer 19

liver mitochondira

Question 20

When are ketone bodies formed?

Answer 20

fatty acids oxidised in TCA cycle

excess acetyl co-A turned to ketone bodies

Question 21

Name three ketone bodies

Answer 21

Acetone
Acetoacetic acid
Beta-hydroxybutyric acid

Question 22

When is ketoacidosis most common?

Answer 22

Type 1 diabetes