BIOC Lecture 2: Insulin

Question 1

What is the key metabolic pathways active in the goldfish when it is producing ethanol?

Answer 1

Glycolysis

Question 2

What is the difference between humans and goldfish’s metabolic rate?

Answer 2

Goldfish have a very reduced metabolic rate, therefore function less efficiently

Question 3

Without oxygen, what do goldfish convert lactate to?

Answer 3

Ethanol

Question 4

What is insulin synthesised as?

Answer 4

A pre-pro-peptide

Question 5

What is a pre-sequence?

Answer 5

A signal that helps tell the cell where this protein is going to go in the cell

Question 6

What is the specific pre-sequence for insulin synthesis?

Answer 6

Responsible for export from the cytosol of the cell into secretory granules

Question 7

What is pro-sequence?

Answer 7

segment of a protein that assists in folding, stabilization, regulation of activity, ensuring the protein is only active under appropriate conditions and at the correct location

Question 8

What is the pro-sequence of insulin important for?

Answer 8

For proper folding of insulin and is then removed

Question 9

Mature insulin has how many chains of amino acids?

Answer 9

2 chains of AA’s - with cleavages

Question 10

Insulin will only function when?

Answer 10

the 2 components are properly folded and connected

Question 11

What type of bonds does insulin have?

Answer 11

disulfide bonds (C-C) as well as secondary and tertiary structure interactions

Question 12

Where are alpha and beta cells made?

Answer 12

Pancreas

Question 13

What do beta cells cause the release of?

Answer 13

Insulin

Question 14

What does insulin lead to?

Answer 14

Decrease in blood sugar

Question 15

What do alpha cells cause the release of?

Answer 15

Glucagon

Question 16

What does glucagon lead to?

Answer 16

Increased blood sugar

Question 17

What does insulin typically form?

Answer 17

Hexamers with Zn in beta cells

Question 18

What does insulin form in the blood?

Answer 18

Monomers

Question 19

What does circulating insulin interact with?

Answer 19

Receptors on some tissues (fat, muscle, liver etc)

Question 20

What is an insulin receptor synthesised as?

Answer 20

One protein - cleaved for full function

Question 21

What gives rise to different receptor isoforms?

Answer 21

Splicing variants during mRNA

Question 22

Where are insulin receptors found?

Answer 22

As a dimer on the surface of various cell types

Question 23

What is a dimer?

Answer 23

when two similar molecules or proteins link up together

Question 24

What three domains play a specific role in the insulin receptors function?

Answer 24

Extracellular, transmembrane, cytosolic

Question 25

What happens when no ligand is present?

Answer 25

The receptor is inactive

Question 26

What does binding of ligand do to receptors?

Answer 26

Causes structural changes and activates receptor (tyrosine kinase domain)

Question 27

What happens in a normal person when blood glucose levels rise?

Answer 27

- Insulin is released by beta cells - Receptor stimulated, GLUT4 receptors move to cell surface - Glucose uptake

Question 28

What is happening in the body of people with Type 1 diabetes?

Answer 28

No functional insulin: autoimmune disease or variant insulin

Question 29

What is happening in the body of people with Type 2 diabetes?

Answer 29

Reduced receptor sensitivity: obesity (common) or rare genetic receptor variants

Question 30

What are beta cells sensitive to?

Answer 30

Insulin sensitive

Question 31

What does the uptake of glucose stimulate?

Answer 31

Oxidative metabolism and production of ATP

Question 32

What does increased metabolic activity stimulate?

Answer 32

The conversion of proinsulin and the release of insulin

Question 33

What do storage granules fuse with?

Answer 33

With membrane and are released into the bloodstream

Question 34

How many glucose transporters are know in humans?

Answer 34

As many as 20

Question 35

How many main transporters are there?

Answer 35

4

Question 36

What are the 4 main glucose transporters?

Answer 36

GLUT 1, 2, 3, 4

Question 37

What is the function of GLUT 1?

Answer 37

Bidirectional and found in foetal tissues. In adults, found in erythrocytes and in low levels in most cells where it allows basal uptake of glucose for respiration

Question 38

Where is GLUT 2 found?

Answer 38

In kidney, liver, pancreatic B cells, basolateral membrane of small intestine

Question 39

What is the function of GLUT 2?

Answer 39

Largely responsible for the insulin-independent uptake of glucose, and for release of glucose during periods of gluconeogenesis.

Question 40

What is the function of GLUT 3?

Answer 40

Glucose uptake in neurones and also in the placenta

Question 41

What is the function of GLUT 4?

Answer 41

Insulin-dependent glucose uptake

Question 42

Where is GLUT 4 found?

Answer 42

In striated muscle and adipose tissue

Question 43

Where does GLUT 4 transition between?

Answer 43

Vesicles within the cell and plasma membrane

Question 44

What are the processes of GLUT4 activation?

Answer 44

Endo- and exocystosis

Question 45

What does insulin favour?

Answer 45

GLUT4 location in plasma membrane