Lecture 18 - Introduction to Protein Metabolism

Question 1

What are 3 causes of a positive nitrogen balance?

Answer 1

1. Growth
2. Pregnancy
3. Lactation

Question 2

What are 3 causes of a negative nitrogen balance?

Answer 2

1. low dietary protein
2. deficiency of essential AA
3. metabolic stress, sepsis, or trauma

Question 3

What are three “ultimate fates” of dietary amino acids in healthy adults?

Answer 3

1. Incorporated into new proteins (specialized products)
2. Broken down and nitrogen excreted as urea (nitrogenous waste)
3. Used for fuel (energy)

Question 4

__________ amino acids are synthesized in the body and not required in the diet.

Answer 4

Non-essential

Question 5

What are two properties of dietary proteins that determine their biological value?

Answer 5

1. Digestibility

2. Content of essential amino acids

Question 6

When large amounts of proteins are ingested, small amounts of amino acids are retained to replace the AAs lost through irreversible pathways.

The rest is excreted into urine as _____ & _______.

Answer 6

urea and ammonia

Question 7

Chronic excess protein can lead to increased _________.

Answer 7

urinary loss of calcium, an osteoporosis

Question 8

Inadequate protein intake causes negative nitrogen balance, edema, and reduced serum ______.

Answer 8

albumin

Question 9

Excess protein can cause an increased workload for what organ in particular?

Answer 9

Kidneys - due to N/S/P molecule filtration (hyperfiltration - a problem in people with renal issues)

Question 10

Obligatory nitrogen losses from the body include urea from alanine and glutamine in breakdown of _________.

Answer 10

muscle protein