Lecture 8

Question 1

Describe a method that can be used to determine which metabolite is being used during respiration.

Answer 1

Substrate metabolism can be measured using an O2 consumed : CO2 released ratio
If the ratio is closer to 1 then the metabolite used is carbohydrate and if closer to 0.7 then it is more fat oxidation

Question 2

How was amino acid oxidation measured in the past? How is it measured now?

Answer 2

Nitrogen balance (Nin vs Nout)
Plasma Urea vs Urea in urine
These methods only give a general idea.
Today stable isotope methodology allows measurement of oxidation and transamination of different amino acids.

Question 3

Why is amino acid metabolism more difficult to study than FA and CHO metabolism?

Answer 3

Each amino acid has its own specific metabolism.

Question 4

What amino acids are typically radioactively labelled?

Answer 4

Essential amino acids are typically used for tracer purposes.

Question 5

How are amino acids used for energy production?

Answer 5

Amino acids like glutamate can be converted into substrates of the kreb’s cycle.

Question 6

Can glutamate be used for energy in muscles?

Answer 6

Yes, a decrease in amount of glutamate in type 1 and type 2 fibers following exercise was discovered meaning glutamate is used for energy.

Question 7

How are glutamate and alanine related during exercise?

Answer 7

decrease in amount of glutamate = increase in amount of alanine.
pyruvate + glutamate -> alanine + alpha ketoglutarate

Question 8

Are all amino acids utilized the same way?

Answer 8

Oxidation rate of different amino acids is different.

Question 9

Does protein breakdown offer much energy for exercise?

Answer 9

Protein contribution to exercise energy expidenture is very minimal

Question 10

What happens to urea production if protein is consumed right before exercise?

Answer 10

Urea production goes up during exercise if lots of protein is consumed before exercise. This indicates that amino acids consumed are utilized for energy production.

Question 11

What effect does Beta adrenergic blockade have on leucine oxidation?

Answer 11

Beta adrenergic blockage increases leucine oxidation.

Question 12

What happens to leucine oxidation under normal circumstances?

Answer 12

Under normal conditions the use of leucine is minimal.

Question 13

How does glycogen availability affect leucine oxidation?

Answer 13

Lower glycogen availability increases leucine oxidation. The contribution of amino acids to overall energy expidenture is still low nevertheless.