Week 7 - Protein

Question 1

Describe the role of amino acids in the body

Answer 1

Amino acids are essential for
- Protein synthesis
- Source of nitrogen,
- Precursors for various molecules like neurotransmitters, hormones, DNA & RNA

Question 2

What is the significance of protein metabolism in the human body

Answer 2

Proteins provide
-Structure to cells,
-Act as enzymes for metabolic reactions,
-Play central roles in organ and tissue metabolism
-Serve as precursors for various important molecules

Question 3

How to calculate nitrogen balance

Answer 3

Determine nitrogen excretion (urine, faeces, sweat in 24h period)
Determine nitrogen intake (protein intake (g) / 6.25) (1g nitrogen = 6.25g protein)
Nitrogen intake - nitrogen excretion

Question 4

How to calculate net protein balance

Answer 4

Determine protein intake
Determine protein excretion (urine, faeces, sweat)
Protein intake - protein excretion

Question 5

Define protein in-balance, + balance, and - balance

Answer 5

Protein in-balance is when protein intake = excretion
Protein + balance is when protein intake > excretion
Protein - balance is when protein excretion > intake

Question 6

What is the recommended protein reference nutrient intake

Answer 6

0.75/g/kg/d

Average in men (1.17)
Average in women (1.07)

Question 7

What are the limitations of calculating nitrogen balance

Answer 7

No information on tissues
Lack of sensitivity (only gross measures of intake and excretion)
Zero balance on low intake may reflect accommodation
Positive balance may not relate to lean body mass
Method used is adequate for determining AA deficiency but not muscle remodelling

Question 8

Difference between protein accretion and protein loss

Answer 8

Muscle protein synthesis > than muscle protein breakdown (protein accretion)
Muscle protein breakdown > muscle protein synthesis (protein loss)

Question 9

What are the synthesis rate of muscle proteins in different pools in the body

Answer 9

1. Mitochondrial (5-10%)
2. Saroplasmic (30%)
3. Muscle Collagen (15%)
4. Myofibrillar (50-60%)

Question 10

What effect does different modes of exercise have on muscle protein synthesis

Answer 10

Resistance exercise increases synthesis of force producing proteins (Myofibrillar)
Endurance exercise increases synthesis of energy producing proteins (Mitochondrial)

Question 11

What are the reasons to optimise protein requirements beyond the RDA for athletes

Answer 11

1. Repair, replace and remodel damaged proteins
2. Optimal function of metabolic pathwats using amino acids
3. Support lean tissue maintenance or accretion
4. Support optimal function of the immune system

Question 12

How does demanding exercise interact with protein intake to stimulate muscle protein synthesis

Answer 12

Demanding exercise stimulates a prolonged elevation of muscle protein synthesis, and in the post-exercise period, the MPS response to protein ingestion is enhanced for 1-2 days post exercise

Question 13

What is the daily protein requirement for strength and power athletes

Answer 13

1.6g/kg/day for optimal protein synthesis. Almost 2x higher than current RDA

Breakpoint for maximum anabolism at 2g/kg/day (2.5 higher than current RDA)

Question 14

What is the sufficient protein ingestion for maximal MPS rates after exercise

Answer 14

30g of protein is sufficient to maximise MPS rates during recovery after single-bout of exercise

or 0.24-0.3g/kg body mass

Question 15

What is the utilisation of ingested amino acids for protein turnover

Answer 15

Ingesting amino acids (protein) can be synthesised along with endogenous amino acids into the intracellular amino acid pool to be used for rebuilding broken-down proteins

Question 16

What are the daily protein requirements for current endurance athletes

Answer 16

2.1 and 2.6g/kg/day
(3.2 fold higher than current EAR and RDA)

Question 17

What are the synthesis rates of muscle protein pools

Answer 17

Muscle protein turnover between 1-2% per day

Healthy man equates to 300-600g of muscle protein

Complete renewal of body protein over 3-4 months

Question 18

What are some myths to high protein diets

Answer 18

Higher protein diet can lead to decline in liver and kidney function
Higher protein diet can cause bone loss

Question 19

How does resistance training affect protein synthesis rates

Answer 19

Protein synthesis is greater in fed state and decline less in fasted state

Question 20

What is the benefit of ingesting protein after endurance training

Answer 20

Enhances aerobic capacity and lean tissue accretion

However no improvement in skeletal muscle oxidative capacity or 10km trial time