Biochemistry Flashcards
What is glucose stored as?
Glycogen
Normal blood glucose levels (range)
3.6 to 5.8 mM
What converts glucose -> glycogen ?
Insulin
During times of feeding, what happens to blood glucose levels?
They increase
- If they increase >5mM then pancreatic beta cells release insulin to convert glucose -> glycogen and thus lower blood glucose levels
Which cells release insulin?
Pancreatic beta cells
Can glucose pass through the plasma membrane unaided?
No
- needs specific transporters e.g. GLUT2, GLUT4
How is energy produced when blood glucose levels rise?
Glucose -> glucose-6-phosphate by glucokinase enzyme. Glucose-6-phosphate then enters the glycolysis cycle and is converted to ATP
What hormones are released after the ingestion of food? (2)
Why are these hormones released?
GIP
GLP-1
Pre-warn the pancreas that lots of glucose is on its way so that the pancreatic beta cells can increase insulin secretion
What is the function of the incretin pathway?
To decrease blood glucose levels by
- increasing insulin secretion from pancreatic beta cells
- decreasing glucagon release by pancreatic alpha cells
What is glycolysis?
Series of enzyme controlled reactions which convert glucose -> pyruvate
Net gain of __ ATP molecules during glycolysis?
2
What is the function of hexokinase?
Increases break down of glucose
Which cells make insulin?
Pancreatic beta cells
Which cells secrete insulin?
Pancreatic beta cells
Where is insulin synthesised?
In the RER of pancreatic beta cells
Example of an ultra short acting insulin?
Lispro
Example of a slow release insulin?
Glargine
When is ultra short acting insulin used?
Allows patients to control their blood glucose levels during a meal
When is slow release insulin used?
At night time, so that the patient’s blood glucose level can be maintained over night
What is the function of insulin?
To convert glucose -> glycogen
When is insulin made?
Synthesised on demand
Synthesised when blood glucose levels increase above 5mM
How is insulin released?
Glucose --> glucose-6-phosphate Glucose-6-phosphate --> ATP K+ATP channels are inhibited Depolarisation of cell membrane Voltage activated calcium channels are opened Calcium floods in to the beta cell This triggers the release of insulin
What happens to insulin levels when blood glucose levels decrease?
Insulin levels decrease
Sympathetic nervous system INCREASES / DECREASES insulin secretion?
Decreases
- when the body is exercising, blood glucose levels are needed
