basic metabolism

Question 1

conc of glucose in blood

Answer 1

~4mM fasting conc rises to ~8mM following a carb-rich meal

Question 2

glycolysis

Answer 2

first stage of catabolic metabolism of glucose, to produce pyruvate

Question 3

conversion of glycose to pyruvate

Answer 3

1) glycolytic reactions:
glucose+ATP->[hexokinase]-> Glucose-6P + ADP.
regulatory checkpoint [product inhibition]
2) isomerism
3)second phosphorylation:
formation of fructose 1,6-Biphosphate by phosphofructo-1-kinase. irreversible, rate limiting. most important control point
4) split from 6 carbons to 2x3 carbons. forms glyceraldehyde 3-phosphate
5) isomerase
6) REDOX and phosphate attachment
- 2 NADH formed per glucose
7) dephosphorylation
- 2 ATP formed per glucose
8) mutase shifts the phosphate group
9) enolase- dehydration to produce high energy intermediate
10) pyruvate kinase catalyses formation of pyruvate and ATP- 3rd irreversible step.

Question 4

anaerobic glycolysis

Answer 4

in anaerobic conditions NADH cannot be oxidized to regenerate NAH+ [requires O2].
NAD+ regenerated by conversion to pyruvate unto lactate

Question 5

the energy balance of glycolysis

Answer 5

aerobic yield:
2x pyruvate [enters TCA cycle] 
2x ATP
2x NADH
- oxidation of NADH in mitochondria yields further 3x ATP each

anaerobic yield:
2x ATP

Question 6

overall reaction of Pyruvate Dehydrogenase

Answer 6

pyruvate + NAD+ +CoA -> [PDH]-> acetyl CoA + NADH + CO2

1) decarboxylation of pyruvate
2) formation of acetyl CoA
3) regeneration of oxidised lipoamide

Question 7

PDH: regulation

Answer 7

• PDH is directly inhibited by NADH and acetyl CoA [product inhibition]
• PDH phosphatase [activates PDH] is activated by Ca++ and insulin
  PDH kinase [deactivates PDH] is: activated by ATP, acetyl CoA and NADH, inhibited by pyruvate
• these therefore inhibit and activate PDH respectively
• commits pyruvate to TCA cycle
• controlled allosterically, covalently, hormonally