Essay Plans Flashcards
Explain the nature of catabolic and anabolic pathways.
Answer
How are glucose and other ‘fuel’ molecules broken down to produce energy?
Fuel molecules include: glucose, glycogen, triacylglycerols and fatty acids, amino acids, ketone bodies.
Explain the role of glycogen as a store of glucose and how its synthesis and degradation are regulated.
Split answer into 3 parts:
1) role of glycogen as a store of glucose
2) regulation of synthesis
3) regulation of degradation
Explain the biosynthesis of glucose by gluconeogenesis, its regulation and relationship to glucose degradation by glycolysis.
Split answer into 3 parts:
1) biosynthesis of gluconeogenesis:
- Say that occurs in cytoplasm.
- Gluconeogenesis is very costly and uses up 4 ATP and 2 GTP for each glucose synthesised
- Explain pathway in words, i.e. Pyruvate is converted to oxaloacetate by pyruvate carboxylase
- explain where the pyruvate comes from (lactate, some amino acids during starvation and glycerol from fats).
- Explain about pyruvate entering the mitochondria and malate and phosphoenolpyruvate leaving to continue gluconeogenesis (alternate pathway to get from pyruvate to phosphoenolpyruvate as part of gluconeogenesis)
2) Regulation:
- Allosteric activation and inhibition of two steps in glycolysis/gluconeogenesis (Fructose-6-phosphate Fructose-1,6-phosphate and Phosphoenolpyruvate Pyruvate (via oxaloacetate for gluconeogenesis)). Important activator/inhibitor is Fructose-2,6-phosphate, along with AMP, ATP, citrate, H+, ADP, Acetyl CoA, Fructose-1,6-phosphate and alanine)
- Bi-functional enzyme with PFK-2 and FBPase activities, which is regulated itself by cAMP-dependent kinase (stimulated by glucagon - stimulates gluconeogenesis and inhibits glycolysis) and phosphatase (stimulated by insulin - inhibits gluconeogenesis and stimulates glycolysis)
3) Relationship to glucose degradation:
- Glycolysis and Gluconeogenesis should not occur at the same time in the same place, because this would be a futile cycle (or substrate cycle) i.e. the hydrolysis of ATP with no useful metabolic reaction occurring.
- The Cori cycle (glycolysis in rapidly contracting muscle (anaerobic conditions) and gluconeogenesis in liver, exchanging lactate and glucose via bloodstream - purpose: removes lactate from muscle and 6 ATP cost of gluconeogenesis is in liver, not muscle))
Explain the different roles of NADH and NADPH in metabolism.
Answer
Explain the regulation of the synthesis and degradation of triacylglycerols, fatty acids and ketone bodies.
Answer
How are amino acids degraded and how is urea produced?
Answer
How are the metabolic pathways integrated to meet the needs of the cell?
Answer
