anabolic processes

Question 1

importance of glucose levels

Answer 1

requires 160-170g per day

supply from glycogen not always sufficient
- between meals
- during longer fasts
- during exercise

needs other ways to make glucose

Question 2

gluconeogenesis

Answer 2

pathway where glucose is synthesised

similar to reverse of glycolysis except not irreversible
need to bypass irreversible reactions

Question 3

gluconeogenesis - 1st bypass

Answer 3

pyruvate to phosphoenolpyruvate

1. carboxylation
   pyruvate - oxaloacetate
   catalysed by pyruvate carboxylase
   - requires biotin
   - requires 1 ATP per pyruvate
2. decarboxylation and phosphorylation
   oxaloacetate - phosphoenolpyruvate
   catalysed by phosphoenolpyruvate carboxykinase
   - 1 GTP needed - source of phosphoric and energy

Question 4

gluconeogenesis - 2nd bypass

Answer 4

fructose 1,6 bisphosphate to fructose
hydrolysis
catalysed by a phosphate fructose 1-6 bisphosphatase
ADP not phosphorylated to ATP
phosphate released

Question 5

gluconeogenesis - 3rd bypass

Answer 5

glucose-6-phosphate to glucose
hydrolysis
catalysed by glucose-6-phosphatase

Question 6

precursors to make glucose in gluconeogenesis

Answer 6

lipid metabolism
- lipolysis to produce fatty acids and glycerol
- usd to make glucose

amino acids
- make glucose from aspartate and other amino acids

lactate
- produced in muscles in exercise
- in liver, converted to pyruvate
- used to make glucose

Question 7

conversion of glycerol to DHAP

Answer 7

glycerol converted to glycerol-3-phosphate
catalysed by glycerol kinase
ATP converted to ADP

glycerol-3-phosphate converted to DHAP
catalysed by glycerol-3-phosphate-dehydrogenase
NAD reduced to NADH

requires 1 ATP and 1 NAD per glycerol

Question 7

what is the glyoxylate cycle?

Answer 7

part of the TCA cycle

bypasses oxidative decarboxylation reactions of the TCA cycle
no carbon atoms from acetyl CoA lost

Question 8

bypasses in the glyoxylate cycle

Answer 8

isocitrate to succinate and glyoxylate
cleaved by isocitrate lyase

acetyl CoA and glyoxylate to malate
catalysed by malate synthase

Question 9

result of glyoxylate cycle

Answer 9

net gain of carbon

2x oxaloacetate (2x4c)
- 1 remains in cycle
- 1 is net gain

Question 10

full glyoxylate cycle

Answer 10

TCA cycle with 2 bypasses of decarboxylation reactions

acetyl CoA
citrate
isocitrate
glyoxylate
malate
oxaloacetate