Protein 1 (wk 7)

Question 1

What are the 8 essential nutrients for humans?

Answer 1

-Water, amino acids, fatty acids, minerals, trace minerals, electrolytes, vitamins and ultra-trace elements

Question 2

What is protein metabolism?

Answer 2

-> Proteins provide structure to all cells in the human body. Many proteins are enzymes that increase the rate of metabolic reactions. Amino acids have central roles in the metabolism of many organs and tissues. Amino acids are precursors for the synthesis of body proteins. Amino acids are precursors and regulators of the synthesis of neurotransmitters, hormones, DNA, and RNA.

Question 3

Draw the protein-balance whole-body:

Question 4

Describe amino acids and the nitrogen balance:

Answer 4

-Amino acids (protein) are a source of nitrogen in the body -> 1g nitrogen= 6.25g protein. Nitrogen (protein) balance: what goes in must, eventually, come out.
-Calculating nitrogen balance ->
1. Determine nitrogen excretion (e.g. urine, faeces, sweat) (in grams per 24h period)
2. Determine nitrogen intake -> protein intake (as grams per day) divided by 6.25
3. N balance = 2 minus 1
+Determine N balance for a number of protein intake levels – can estimate the protein intake required to maintain protein balance

Question 5

What are limitations of nitrogen balance?

Answer 5

-> No information of tissues. Lack of sensitivity – only gross measures of intake and excretion. Zero balance on low intake may reflect accommodation (similar to low EA concept). Positive balance may not relate to lean body mass.
+NBAL adequate to measure AA required to prevent ‘deficiency’. NBAL may be inadequate for estimating AA requirements for exercise-induced muscle remodelling.

Question 6

Draw the utilization of ingested amino acids for protein turnover:

Question 7

Net protein balance:

Answer 7

-Net protein balance = MPS- MPB
-MPS > MPB + net protein balance (protein accretion)
-MPB < MPS = -net protein balance (protein loss)