Biochem

Question 1

function of beta cells

Answer 1

secrete insulin

Question 2

function of alpha cells

Answer 2

secrete glucagon

Question 3

function of delta cells

Answer 3

secrete somatostatin

Question 4

function of PP cells

Answer 4

secrete pancreatic polypeptide

Question 5

describe the production of insulin

Answer 5

synthesised in the rough ER of beta cells as preproinsulin
cleaved twice to form insulin + C-peptide
C-peptide is secreted along with insulin and is a waste product which can be measured to assess insulin levels

Question 6

describe the secretion of insulin

Answer 6

glucose enters the beta cell via GLUT2 
phosphorylated to glucose-6-phosphate by glucokinase 
metabolised to produce ATP 
closes K-ATP channels 
depolarises cell membrane 
Ca2+ channels open 
secretory vesicles fuse with cell membrane 
insulin is released

Question 7

potassium channels consist of which 2 proteins

Answer 7

inward rectifier unit (Kir) which is the pore subunit
sulphonylurea receptor (SUR1) which is the regulatory subunit

Question 8

what is the effect of a mutation causing overactive K-ATP channels

Answer 8

profound neonatal diabetes

Question 9

what is the effect of a mutation causing inactive K-ATP channels

Answer 9

hyperinsulinaemia

Question 10

what is MODY

Answer 10

monogenic diabetes with a genetic defect in beta cell function
familial early onset type 2 diabetes
primary defect in insulin secretion

Question 11

mutation in MODY1

Answer 11

HNF-4a

Question 12

mutation in MODY2

Answer 12

glucokinase

Question 13

mutation in MODY3

Answer 13

HNF-1a

Question 14

mutation in MODY4

Answer 14

IPF1

Question 15

mutation in MODY5

Answer 15

HNF-1b

Question 16

mutation in MODY6

Answer 16

neuroD1

Question 17

what is happening in type 1 diabetes

Answer 17

antibodies which destroy the insulin secreting beta cells in the pancreas

Question 18

what is happening in MODY

Answer 18

defective glucose sensing in the pancreas and/or loss of insulin secretion

Question 19

what is happening in type 2 diabetes

Answer 19

hyperglycaemia with hyperinsulinaemia so primary problem is reduced insulin sensitivity in tissues

Question 20

describe insulin signalling

Answer 20

insulin binds to alpha subunit of tyrosine kinase receptor
beta subunits are autophosphorylated
IRS is phosphorylated
IRS activates Ras/MAPK pathway and gene expression
IRS activates PI3K, PKB and glycogen synthesis
PKB stimulates GLUT4 translocation
glucose is taken up and cell growth is stimulated

Question 21

what do kinases do

Answer 21

phosphorylation

Question 22

which amino acids can phosphorylation occur on

Answer 22

serine
threonine
tyrosine

Question 23

which bonds link the alpha and beta subunits of the insulin receptor

Answer 23

disulphide bonds

Question 24

where are ketone bodies formed

Answer 24

liver mitochondria

Question 25

what are ketone bodies derived from

Answer 25

acetyl-coA during beta oxidation