Blood glucose concentration (16) Flashcards
What are the 2 reasons for why blood glucose concentration must remain stable?
- to be able to maintain constant blood water potential in order to prevent osmotic lysis/crenation of cells
- to be able to maintain constant concentration of the respiratory substrate so organism maintains constant level of activity regardless of environment
What are 3 factors that affect blood glucose concentration?
1) amount of carbohydrate digested from diet
2) rate of glycogenolysis
3) rate of gluconeogenesis
What are the 3 processes involving the liver and glucose?
glycogenesis
glycogenolysis
gluconeogenesis
What happens in glycogenesis?
liver converts glucose into glycogen
What happens in glycogenolysis?
liver hydrolyses glycogen into glucose which can diffuse into blood
What happens in gluconeogenesis?
liver converts glycerol and amino acids into glucose
What are the 3 steps that happen when blood glucose concentration decreases?
1) alpha-cells in islets of Langerhans in pancreas detect decrease and secrete glucagon into bloodstream
2) glucagon binds to surface receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis
3) glucose diffuses from liver into bloodstream
What are the 2 steps that happen when blood glucose concentration increases?
1) Beta-cells in islets of Langerhans in pancreas detect increase and secrete insulin into bloodstream
2) insulin binds to surface receptors on target cells which increases cellular glucose uptake, activates enzymes for glycogenesis and stimulates adipose tissue to synthesise fat
What is the role of adrenaline when blood glucose concentration decreases?
1) adrenal glands produce adrenaline which binds to surface receptors on liver cells and activates enzymes for glycogenolysis
2) glucose diffuses from liver into bloodstream
How does insulin lead to an increase in blood glucose concentration?
- increases permeability of cells to glucose
- increases glucose concentration gradient
- triggers inhibition of enzymes for glycogenolysis
How does insulin cause an increase in permeability of cells to glucose?
- increases number of glucose carrier proteins
- triggers conformational change which opens glucose carrier proteins
How does insulin cause an increase in glucose concentration gradient?
- activates enzymes for glycogenesis in liver and muscles
- stimulates fat synthesis in adipose tissue
What are the 5 steps on how glucagon and adrenaline work using the secondary messenger model?
1) hormone-receptor complex forms
2) conformational change to receptor activates G-protein
3) activates adenylate cyclase which converts ATP to cyclic AMP (cAMP)
4) cAMP activates protein kinase A pathway
5) results in glycogenolysis
What is the cause of Type 1 diabetes?
body cannot produce insulin
What’s a reason why the body might not be able to produce insulin?
due to autoimmune response which attacks beta-cells of islets of Langerhans
