Amino Acid

Question 1

Avg turnover of protein in adults

Answer 1

300-400g per day

Question 2

What are the rough half-lives of different types of proteins

Answer 2

Most - days
Structural eg collagen - years
Hormones and digestive enzymes - degraded in minutes

Question 3

What is the recommended protein intake

Answer 3

50-70g

Question 4

What is positive nitrogen balance and when does it occur

Answer 4

Nitrogen synthesis > excretion

Child growth
After serious illness
After immobilisation due to an accident
Pregnancy

Question 5

How are foreign, exogenous proteins broken down

Answer 5

1Taken into vesicles by Endocytosis or Autophagocytosis

2. fuse with vesicles containing PROTEOLYTIC ENZYMES which degrade proteins to amino acids

Question 6

What increases rate of protein breakdown

Answer 6

Starvation and Hormones eg cortisol increases protein breakdown in muscle

Question 7

What are amino acids degraded to initially

Answer 7

NH2 and oxo acid (keto acid)

Question 8

Oxidative deamination equation

Answer 8

Amino acid + water + coenzyme —> keto acid + ammonia + coenzyme-2H

Question 9

Trans animation equation

Answer 9

Amino acid 1 + keto acid 2 —> amino acid 2 + keto acid 1

Question 10

** Explain the concept of nitrogen balance

Answer 10

the rate of body protein synthesis (and other N- containing compounds) is equal to the rate of degradation.

Question 11

4. Explain how amino acids are classified as essential or nonessential and the significance of this classification;

Answer 11

essential amino acids = not made by the body so must be in diet
-non essential; humans synthesis 10 from intermediates

Question 12

5. Explain the terms transamination and deamination

Answer 12

• trans: N part of the amino acid is removed by transfer to an acceptor molecule
• deamination: RELEASE OF NH2 GROUP AS AMMONIA NH3 or NH4+

Question 13

what are the causes of negative nitrogen balane

Answer 13

• in starvation,
• during serious illness,
• In late stages of some cancers,
• in injury and trauma.
• If not corrected and becomes prolonged, there will be irreversible loss of essential body tissue
• lead to death.

Question 14

7. Explain the importance of glutamine

Answer 14

• safe carrier of ammonia
• carry 2 amminia equivilants to liver - urea
• deiver amminium ions to kidney for buffering

Question 15

5. Explain transdeamination

Answer 15

transamination followed by oxidative deamination.

yields pyrvuate, and glutamate.

Question 16

what system removed old or damaged proteins

Answer 16

ubiquitin breakdown system

gives mixture of amino acids

Question 17

what are ketogenic amino acids

Answer 17

only degraded into acetyl CoA

leucine and lysine

Question 18

what are glycogenic amino acids

Answer 18

in starvation, amino acids w carbon skeletons of 13 of the amino acids are converted back to glucose

Question 19

what are both glycogenic and ketogenic

Answer 19

phenylalanine and tyrosine - part of their structure converted to glucose
(also typtophan, threonine and isoleucine)

Question 20

role of liver in N metabolism

Answer 20

1. remove aa, glc and fat from portal blood supply
2. absorb aa for protein synthesis
3. synth plasma proteins
4. synth ahem, purines and pyrimadines - RNA and DNA
5. degrade excess aa - Transdeamination
6. NH3 –> urea for excretion. ornithine cycle

Question 21

examples of plasma proteins

Answer 21

albumin
clotting factor
lipid transport proteins

Question 22

examples of plasma proteins

Answer 22

albumin
clotting factor
lipid transport proteins

Question 23

what are amine groups NH2 transported as in the blood

Answer 23

glutamine

Question 24

what organ converts amino groups to urea

Answer 24

liver

Question 25

what are important amino acid in interurban transport of nitrogen

Answer 25

alanine
glutamate
glutamine
aspartate

Question 26

what are the 4 end products of nitrogen metabolism

Answer 26

• urea - protein breakdown
• creatinine - creatine phosphate
• uric acid - DNA and RNA
• amminium NH4 - control body pH

Question 27

why is ammonIA dangerous?

Answer 27

neurotoxic

• cerebral oedema, coma and death
• cell death

Question 28

what is hyperammonaemia

Answer 28

impaired conversion of Nh3 to urea

Question 29

what does hypermminaemia cause

Answer 29

-liver failure (viral hepatitis, ischaemia, liver cirrhosis,
toxins eg aflatoxin in mouldy peanuts)
-genetic defects (reduce catalytic activity of any enzyme of the urea cycle)

Question 30

what is an X-linked inheritance, example of genetic defect caused by hyperammonaemia

Answer 30

ornithine transcarbamoylase deficiency

1 in 30,000 live births