Flashcards in Biochemistry Deck (48)
What cells release glucagon?
What are the 4 types of endocrine cell in the pancreas?
beta cells; alpha cells; PP cells; delta cells
What do the delta cells release?
What do the PP cells release?
What is synthesised at the RER in beta cells?
What are the 3 parts of the preproinsulin?
two polypeptide chains and a connecting peptide
what type of bonds link the two polypeptide chains?
What is the most rapidly acting insulin?
What insulin is administered as a single bedtime dose?
What is the graph of action for insulin glargine like?
a peakless prolonged action
What transporter does glucose enter the beta cells by?
What happens to glucose when it enters the cell?
it is phosphorylated by glucokinase and then undergoes oxidative phosphorylation
How many ATP are produced per glucose?
What is the function of ATP in the beta cell?
ATP inhibits the ATP-sensitivie K+ channel Katp
What does inhibition of the Katp channel lead to?
depolarisation of the cell membrane
What does depolarisation of the cell membrane result in?
opening of the voltage-gated caclium channels
What does the intracellular calcium do?
leads to fusion of secretory vesicles with the cell membrane adn release of insulin
Why is the release of insulin biphasic?
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
What are the 2 proteins taht form the Katp channel?
the pore subunit- Kir6 and the regulatory subunit-SUR1
Which part of the Katp channel does the ATP bind to?
What class of drugs can bind to the SUR1 and inhibit the channel?
What drug stimulates the Katp channel?
What effect does diazoxide have?
inhibits insulin secretion as the membrane is not depolarised by keeping the K inside
What would Kir6 mutations that result in activated Katp channels or increase in Katp numbers result in?
neonatal diabetes (insulin wouldnt get released as no depolarisation)
What is MODY?
monogenic diabtes with genetic defect in beta cell function
What is the difference between type 1 diabetes and MODY?
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
What is type 2 diabetes?
intially hyperglcaemia with hyperinsulinamia then there is reduced insulin sensitivity in tissues
What are the biological effects of insulin?
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
Is insulin an anabolic or catabolic hormone?