Biochemistry

Question 1

What cells release glucagon?

Answer 1

alpha cells

Question 2

What are the 4 types of endocrine cell in the pancreas?

Answer 2

beta cells; alpha cells; PP cells; delta cells

Question 3

What do the delta cells release?

Answer 3

somatostatin

Question 4

What do the PP cells release?

Answer 4

pancreatic polypeptide

Question 5

What is synthesised at the RER in beta cells?

Answer 5

preproinsulin

Question 6

What are the 3 parts of the preproinsulin?

Answer 6

two polypeptide chains and a connecting peptide

Question 7

what type of bonds link the two polypeptide chains?

Answer 7

disulfide bonds

Question 8

What is the most rapidly acting insulin?

Answer 8

insulin lispro

Question 9

What insulin is administered as a single bedtime dose?

Answer 9

insulin glargine

Question 10

What is the graph of action for insulin glargine like?

Answer 10

a peakless prolonged action

Question 11

What transporter does glucose enter the beta cells by?

Answer 11

GLUT2 transporters

Question 12

What happens to glucose when it enters the cell?

Answer 12

it is phosphorylated by glucokinase and then undergoes oxidative phosphorylation

Question 13

How many ATP are produced per glucose?

Answer 13

36

Question 14

What is the function of ATP in the beta cell?

Answer 14

ATP inhibits the ATP-sensitivie K+ channel Katp

Question 15

What does inhibition of the Katp channel lead to?

Answer 15

depolarisation of the cell membrane

Question 16

What does depolarisation of the cell membrane result in?

Answer 16

opening of the voltage-gated caclium channels

Question 17

What does the intracellular calcium do?

Answer 17

leads to fusion of secretory vesicles with the cell membrane adn release of insulin

Question 18

Why is the release of insulin biphasic?

Answer 18

only 5% of insulin granules are immediately available for release, reserve pool must undergo preparation to become mobilised, if blood sugar is not stabilised by inital release

Question 19

What are the 2 proteins taht form the Katp channel?

Answer 19

the pore subunit- Kir6 and the regulatory subunit-SUR1

Question 20

Which part of the Katp channel does the ATP bind to?

Answer 20

Kir6 part

Question 21

What class of drugs can bind to the SUR1 and inhibit the channel?

Answer 21

sulphonylurea

Question 22

What drug stimulates the Katp channel?

Answer 22

diazoxide

Question 23

What effect does diazoxide have?

Answer 23

inhibits insulin secretion as the membrane is not depolarised by keeping the K inside

Question 24

What would Kir6 mutations that result in activated Katp channels or increase in Katp numbers result in?

Answer 24

neonatal diabetes (insulin wouldnt get released as no depolarisation)

Question 25

What is MODY?

Answer 25

monogenic diabtes with genetic defect in beta cell function

Question 26

What is the difference between type 1 diabetes and MODY?

Answer 26

type 1 is a loss of insulin secreting beta cells and MODY is a defective glucose sensing in the pancreas and/or loss of insulin secretion

Question 27

What is type 2 diabetes?

Answer 27

intially hyperglcaemia with hyperinsulinamia then there is reduced insulin sensitivity in tissues

Question 28

What are the biological effects of insulin?

Answer 28

amino acid uptake in muscle; DNA synthesis; protein synthesis; growth responses; glucose uptake in muscle and adipose tissue; lipogenesis in adipose tissue and liver. turns off lipolysis and gluconeogenesis

Question 29

Is insulin an anabolic or catabolic hormone?

Answer 29

anabolic

Question 30

On what group do proteins get phosphorylated?

Answer 30

hydroxyl group

Question 31

What amino acids are able to be phosphorylated?

Answer 31

serine; threonine; tyrosine

Question 32

Why does adding phosphate change the structure of the protein?

Answer 32

introduces a large negative charge into the protein structure

Question 33

What is the insulin receptor made up of?

Answer 33

a dimeric tyrosine kinase- two extracellular alpha subunits with insulin binding domains and two transmembrane beta subunits

Question 34

What bond links the alpha and beta subunits?

Answer 34

disulfide bonds

Question 35

What does binding of the insulin to the receptor cause?

Answer 35

causes them to phosphorylate themselves (autophosphrylation thus actiavting the catalytic activity of the recetpor

Question 36

What does the phosphorylated receptor then do?

Answer 36

phosphorylates the insulin receptor substrates

Question 37

What do the phosphorylated IRS-1 proteins activate?

Answer 37

the Ras/MAPK pathway and gene expression; PI3K,PKB and glycogen synthesis

Question 38

What does PKB do?

Answer 38

causes the translocation of GLUT4 receptors and glucose to enter the cell

Question 39

What is the key mediator of insulin sensitivity?

Answer 39

adipose functionality

Question 40

Wh is it believed that adipose functionality is the key mediatory of insulin sensitivity?

Answer 40

because seever insulin resistance occurs with obesity as well as with complete absence of adipose tissue

Question 41

What is leprechaunism-donohue syndrome?

Answer 41

a rare autosomal recessive gene in the insulin receptor leads to severe insulin resistance

Question 42

What are the developmental abnormalities associated with leprechaunism-donohue syndrome?

Answer 42

elfin facial appearance; growth retardation; absence of subcutaneous fat, decreased muscle mass

Question 43

What is rabson medenhall syndrome?

Answer 43

rare autosomal recessive genetic trait that causes severe insulin resistance hyperglycaemia and compensatory hyperinsulinaemia

Question 44

Where are ketone bodies formed?

Answer 44

in liver mitochondria

Question 45

What are ketone bodies derived from?

Answer 45

from acetyl-CoA from beta oxidation

Question 46

What are ketone bodies used for in the body?

Answer 46

important molecules of energy metabolism for heart muscle and renal cortex

Question 47

What causes the acidosis in ketone production?

Answer 47

they form acid in the blood and the high glucose excretion causes dehydration which exacerbates acidosis

Question 48

Why don't you get ketoacidosis in type 2 diabetes?

Answer 48

high concentrations of insulin in type 2 diabetes inhibits hormone-sensitive lipase