Biochemistry Flashcards
What is the normal level of blood glucose?
5mM
Which pancreatic cells are the main insulin producers?
Beta-cells
What is cleaved off proinsulin to yield insulin?
C (connecting) peptide
Insulin lispro has a lysine and a proline residues reversed. It is fast/slow and short/long acting
fast and short acting
Insulin glargine precipitates in the subcutaneous tissue. It is ______ acting. How many doses are required?
ultra-long acting
1 dose /day
What enzyme acts as a glucose sensor? How?
Glucokinase
- A small change in glucose concentration triggers a large increase in glucokinase activity
- Increased glucose metabolism increases ATP levels
- ATP inhibits ATP-sensitive K+ channels (Katp), causing cell membrane depolarisation
- Ca2+ channels open in response to depolarisation
- Ca2+ influx leads to fusion of secretory vesicles and insulin exocytosis
In T2DM the beta cells lose the ability to secrete insulin (T/F)
False
- insulin is produced
- hyperglycaemia means that glucokinase loses ability to respond to fluctuations in glucose concentrations
Release of insulin is biphasic. Why are there 2 phases of insulin release?
There are two insulin pools:
- Readily releasable pool (5%)
- Reserve pool - preparatory reactions are required for its release
Beta cells (in pancreas) only secrete insulin when they detect a fall in glucose below 5mM (T/F)
False
Beta cells produce insulin in response to high glucose levels, >5mM
T1DM results in the loss of beta cells (T/F)
True
-autoimmune destruction of beta cells
Sulphonylurea drugs (e.g. Tolbutamide) are used in T2DM treatment. What is their mode of action?
Katp channel inhibitors
- mimic action of ATP to depolarise beta cells
- depolarisation triggers insulin secretion
MODY (maturity-onset diabetes of the young) is a form of early onset _______ diabetes, characterised by defects in ______ ______ function and/or loss of _____ _____
Type II diabetes
defects in Beta cell function
and / or
loss of insulin secretion
What is impaired in MODY2? What are the implications?
Glucokinase mutations cause diminished sensitivity to rising glucose levels
-insulin is secreted at higher glucose levels
What are the glucose uptake channels in Beta cells?
GLUT2 channels
HNF Transcirption factors mutations are present in MODY 1 and 3. These TFs regulate differentiation and function of…
Beta cells