Amino Acid Metabolism Lecture 14

Question 1

What is Nitrogen Balance?

Answer 1

It is a method if determining the rate of protein turnover in the body.

Question 2

How can nitrogen balance determine the rate of protein turnover in the body?

Answer 2

Urea, which is a bi product of AA breakdown is able to be measured in the sweat, urine and feces. = Loss

Protein intake is measured, too = INtake

The recycling of AA cant be determined i.e protein turnover is higher than calculated

Question 3

When we are not in nitrogen balance what occurs?

Answer 3

Positive nitrogen balance = weight gain

Negative nitrogen balance = weight loss

Question 4

Does protein intake = the protein breakdown?

Answer 4

No, as a lot of amino acids are recycled and the size of breakdown usually far exceeds intake

Question 5

How can you measure protein turnover to calculate RDI of protein?

Answer 5

Measuring the quantity of urea lost from the body allows you to determine the amount of protein needed in the diet. I.e when urea loss is 0 then you know whatever protein intake you have then is what you need daily.

Question 6

What is protein intake measured in?

Answer 6

g per KG per day

Question 7

How can you measure the degradation of muscle protein?

Answer 7

3-methyhistadine excretion (a biproduct of AA metabolism, cannot be recycled and is therefore excreted in the urine, thus we can calculate muscle damage.)

Question 8

How can the rate of protein synthesis be determined?

Answer 8

Using radioisotopes or tracer isotopes can determine where the amino acids end up that are of interest and can calculate the rate of protein synthesis

Question 9

What is required to build, repair and recover muscle?

Answer 9

Positive protein balance

• This results in increased muscle protein synthesis or decreased muscle breakdown

Question 10

Under fasting conditions comparing exercise vs resting, what happens to protein turnover?

Answer 10

During fasting protein balance is always negative regardless of activity. However protein balance is less negative in exercising fasting

Question 11

What happens to protein balance in a sedentary person vs exercising person, both whom eat RDI protein?

Answer 11

Protein synthesis occurs in both states except its greater in exercising state.

Question 12

After exercise when does protein synthesis occur?

Answer 12

Protein synthesis only occurs if feeding occurs and necessary protein intake is achieved.

Question 13

So should post exercise meals just be protein?

Answer 13

No they must be balanced i.e have mainly CHO and some fats to develop a favorable hormonal environment i.e insulin

Question 14

How much does protein contribute to energy providing at rest?

Answer 14

5-15%

Question 15

What happens to protein energy supply during exercise?

Answer 15

It dramatically decreases as proteins are very inefficient to ‘burn’

However very long endurance sees a slight increase in protein energy up to 10%

Question 16

What is the protein requirements of sedentary people, endurance athletes and strength builders?

Answer 16

Sedentary = 0.8 g KG BM Day
Endurance = 1.2-1.7 g.kg.BM.DAY
Strength = 1.6-1.8 g.kg.bm.day

These can all be achieved through normal diet alone

Question 17

How much habitually does a games player consume in protein?

Answer 17

1.5gkgbmday

Question 18

How much habitually does a endurance cyclist consume in protein?

Answer 18

3.0gkgbmday

Question 19

How much habitually does a bodybuilder consume in protein?

Answer 19

2.5gkgbmday

Question 20

Which groups of athletes are likely to be protein deficient?

Answer 20

Amnnorheic female runners
Male wrestlers
F AND M gymnists

Some vegeterians

Question 21

Does an athete who undertakes huge amounts of exercise need more protein

Answer 21

No, they are adapted and oxidate less protein

Question 22

Does an endurance athlete need more protein i.e supplement?

Answer 22

No their natural diet will mostly ensure they get enough

Question 23

Do strength athletes need more protein?

Answer 23

No they get enough in the diet

Question 24

WHy do some studies say strength athletes need more protein?

Answer 24

These studies use non-trained athletes and this results in the follow up days being in nitrogen loss, because their muscles are very damaged with this new intense exercise, but if the exercise is sustained with the same protein intake dietary is enough and protein turnover becomes balanced.