Extra things you need to know Flashcards
Deamination of all 20 amino acids results in the production of 7 molecules
1) pyruvate
2) Acetyl CoA
3) Acetoacetyl CoA
4) succinyl CoA
5) fumerate
6) oxaloacetate
7) alpha - ketoglutarate
Why can’t fatty acids be converted into glucose by gluconeogenesis?
Because fatty acid metabolism gives rise to acetyl CoA. This enters the TCA cycle combining with oxaloacetate to give citrate, and as the cycle progresses, two carbons are lost as CO2 before oxaloacetate is regenerated. Thus there is no net production of oxaloacetate and therefore pyruvate required for gluconeogenesis.
During exercise, what enzyme in muscle demands more ATP? and how does the body respond to this?
Actomyosin ATPase
The body responds to this increased demand by increasing the number of glucose transporters in the membranes of muscle cells
What does adrenaline do to help meet the demand for ATP?
1) Increased glycolysis in muscle cells
2) Increased gluconeogenesis in liver
3) Increased release of fatty acids from adipocytes
What happens when exercising under anaerobic conditions?
1) ATP demand cannot be met by oxidative phosphorylation/ O2 delivery
2) Transport of glucose from the blood is not enough for the demand from glycolysis
3) Increased muscle breakdown if glycogen
4) Pyruvate converted to lactate by lactate dehydrogenase in muscles to replenish NAD+ levels and maintain glycolysis
5) Lactate taken up by liver and converted to pyruvate for gluconeogenesis
What are the different isoforms of hexokinase found in muscle and liver?
hexokinase I - muscle
hexokinase IV - liver
What are the differences between these two isoforms?
Hk I (muscle ) - high affinity for glucose (Km of 0.1mM) and very sensitive to inhibition by glucose-6-phosphate. This makes sense because under anaerobic conditions, when the rate of the TCA cycle drops, glycolysis should also slow which is accomplished by the accumulating levels of glucose-6-phosphate.
Hk IV (liver) - low affinity for glucose (Km 4mM) and less sensitive to the inhibitory effects of glucose-6-phosphate.
What does increased insulin secretion result in?
1) Increased glucose uptake by muscles and glycogen synthesis
2) Increased glucose uptake for glycogen synthesis and glycolysis in liver. Glycolysis produces Acetyl CoA which is used to synthesise fatty acids
3) Increased triglyceride synthesis in adipose tissue
What happens during prolonged fasting (5)?
1) glucagon/insulin ratio increases
2) concentration of TCA cycle intermediates reduced to provide substrate for gluconeogenesis
3) protein breakdown to provide amino acid substrate for gluconeogenesis
4) adipose tissue begins to hydrolyse trigylcerides to provide alternative metabolic fuel and preserve glucose for brain
5) ketone bodies produced from fatty acids and amino acids in liver to partially substitute for glucose metabolism in brain
Give 4 complications of diabtes mellitus
1) hyperglycaemia which impacts on retina, kidney, peripheral nerves
2) increased ketone bodies with risk of acidosis
3) increased in plasma fatty acids and lipoproteins with potential cardiovascular risks
3) hypoglycaemia with subsequent coma if insulin dose not perfectly controlled
What can Acetyl CoA be used for?
1) to make ketone bodies
2) to make sterols and fatty acids
3) to go in the TCA cycle
4) To acetylate protein residues
How many ATP formed from glucose metabolism?
38 in total
4 from glycolysis
24 from Kreb’s
