T2 L10: regulation and carbohydrate metabolism Flashcards
Where does gluconeogenesis occur?
In the liver and kidneys
What are the 2 requirements for gluconeogenesis?
A source of carbon and a source of energy
What are the sources of carbon for gluconeogenesis?
Lactate, amino acids or glycerol released from triglycerides by lipolysis in adipose tissue
What is the energy source for gluconeogenesis?
Provided by the metabolism of fatty acids (beta-oxidation generates ATP)
What is ammonia converted to in the liver?
Urea and then passed out of the bloodstream through urine
What is fumarate converted to?
Into oxaloacetate in the cytoplasm
What is the equation for the production of urea?
NH3 + CO2 + 2H2O + 3ATP + aspartate = urea + fumarate +2ADP + AMP + 2Pi + PPi
Which molecules allosterically regulate PFK-1?
Subject to energy dependent allosteric regulation by ATP, AMP, H+, Fru-6-P, Fru-2,6-BP and Citrate
What’s meant by allosteric regulation?
Regulation of enzymes by molecules present in the cell
Why does ATP allosterically inhibit PFK-1?
Because it’s a sign of high energy levels in muscles.
Why does AMP allosterically active PFK-1?
It’s a sign of low energy in muscles
What is anoxia?
insufficient O2 supply
Why does H+ allosterically inhibit PFK-1?
[H+] increases during anoxia or anaerobic respiration so it inhibits glycolysis to prevent the pH from falling too low and from damaging the cells
What can overcome high [H+] in cardiac muscle so it continues beating?
High AMP levels. This results in cellular damage and angina but the heart can’t stop beating
How does Fru-6-P allosterically control PFK-1?
Fru-6-P activates PFK-1 because it’s a sign of high glucose levels so glycolysis is stimulated to use up that glucose
How does Fru-2,6-BP allosterically control PFK-1?
Fru-2,6-BP activates PFK-1 because it’s a sign of high glucose levels so glycolysis is activated to use up that glucose
Which molecule is the most potent allosteric activator known in glucose metabolism?
Fru-2,6-BP
Hoe does Citrate allosterically control PFK-1?
Citrate inhibits PFK-1. Its a sign of that there is more CoA that can be oxidised like in starvation so glucose is conserved
Why do all cells have PFK-1, PFK-2, and F-2,6-BPase?
Because all cells require glucose
Why do only liver and kidney cells have F-1,6-BPase?
Because that’s where gluconeogenesis takes place. F-1,6-BPase is an enzyme for gluconeogenesis
What is fructose-2,6-phosphate synthesised from and using which enzyme?
From fructose-6-phosphate using PFK-2
Which molecule is the most potent allosteric inhibitor of PFK-1?
Fructose-2,6-phosphate
What does cAMPPK do?
It activates F-2,6-BPase and deactivates PFK-2
Which 2 enzymes involved in glycolysis are attached and are the same molecule?
PFK-2 and F-2,6-BPase. Phosphorylation inhibits PFK-2 and stimulates F-2,6-BPase
What does PFK-2 do?
Synthesises F-2,6-BP
What stimulates gluconeogenesis in the short term?
Adrenaline and glucagon
How is gluconeogenesis inhibited in the short-term?
Insulin
What stimulates gluconeogenesis in the long term?
Glucagon, glucocorticosteroids, and thyroid hormones
