L13: Metabolic Integration

Question 1

Glucose metabolism

Answer 1

1. Glycolysis / gluconeogenesis —> pyruvate, 2 net ATP
2. TCA cycle (Krebs/citric acid) —> 3 NADH, 1 FAD2H
3. Oxidative phosphorylation —> ATP
4. Pentose phosphate pathway —> NADPH, ATP, Pentose phosphate for nucleic acid synthesis
5. Glycogenesis / Glycogenolysis —> glycogen (glycoconjugates) from UDP glucose
6. Produce TAG (glycerol + FA from TCA cycle) + Amino acids

Question 2

Amino acid metabolism

Answer 2

1. Protein
2. Become Pyruvate/Acetyl-CoA, fed into TCA cycle to produce ATP
3. Glucose (carbon skeleton of glucogenic a.a.: Tyrosine, Phenylalanine, Isoleucine)
4. Ketone bodies (carbon skeleton of ketogenic a.a.: Tyrosine, Phenylalanine, Isoleucine)
5. Nitrogen-containing compound
   - glutathione
   - Creatine —> Creatine phosphate
   - monoamine neurotransmitter e.g. dopamine, noradrenaline, adrenaline, serotonin

Question 3

Fat metabolism

Answer 3

With oxygen:
Fatty acid —(β oxidation)—> Acetyl CoA, NADH, FADH2
Fatty acid —> TAG (storage)

Fasting:
TAG —> Fatty acid —> Ketone bodies —> ATP
TAG —> Glycerol —> Glucose —> ATP

Question 4

Metabolism of Fuels in Heavy burst of activity

Answer 4

1. ATP (directly used)
2. Creatine phosphate (convert ADP to ATP and used)
3. Muscle Glycogen (Ca, AMP, Stress hormone)—> Glucose —> G-6-P —> F-6-P —> F-1,6-BP (PFK1, stimulated by AMP) —> Pyruvate —> Lactate (then transported to liver)

Cori-cycle: (Glucose ⇌ Lactate)
Muscle: Glucose —> Pyruvate —> Lactate (transported to liver)
Liver: Lactate —> Glucose (gluconeogenesis —> transported back to muscle)

Question 5

Metabolism of Fuels in Moderately intense and less intense, prolonged activity

Answer 5

Moderately intense:

1. ATP
2. Creatine phosphate
3. Muscle Glycogen —> Glucose —> Pyruvate —> TCA cycle —> Oxidative phosphorylation

Less intense, prolonged:

1. Liver Glycogen
2. Amino acids (muscle) (***Pyruvate ⇌ Alanine cycle)
   - Muscle: Amino acids —> α-ketoacids (via Glucose —> Pyruvate —(transamination)—> Alanine)
   - Liver: Alanine —(deamination)—> Pyruvate + NH3 —> Glucose (transported back to muscle)
3. Fatty acids (Stress hormone: adipose tissue TAG —> Glycerol + FA)

Question 6

After a meal, During fasting

Answer 6

After a meal: (Glycogenesis, Glycolysis)
Glucose —> Glycogen (Storage)/ Pyruvate (ATP)/ Pentose phosphate/ A.A./ Glycerol
Fat —> TAG —> Fatty acid —> β oxidation
Fat —> TAG —> VLDL —> TAG in adipose tissue (storage)
A.A. —> Protein / Pyruvate / Glucose / Ketone bodies / Nitrogen containing compound

Fasting: (Glycogenolysis, Gluconeogensis)
Glycogen —> Glucose —> pyruvate —> ATP
Protein —> A.A. —> ketone bodies / pyruvate / Acetyl-CoA / glucose —> ATP
TAG —> Glycerol —> Glucose —> ATP
TAG —> Fatty acid —> Ketone bodies —> ATP