Nitrogen

Question 1

What is the main nitrogen-containing molecules of the body

Answer 1

Proteins
Nucleic acids/nucleotides
Biologically active amines
Haem-containing molecules

Question 2

What happens to dietary proteins

Answer 2

Enymatically hydrolyzed into amino acids, dipeptides, tripeptides

Question 3

What are non-essential and essential amino acids

Answer 3

Non-essential - 11 amino acids synthesised in body
Essential - 9 amino acids need to be consumed in diet

Question 4

Describe the catabolism of body proteins

Answer 4

Misfolded, foreign/Unwanted proteins have same end point as dietary proteins, individual amino acids
Known as body protein turnover

Question 5

What is the role of glutamate

Answer 5

Allows fixed nitrogen to flow to other biomolecules
Glutamate only amino acid that obtain nitrogen directly from ammonium ion

Question 6

How is nitrogen transferred to, from and between amino-acids

Answer 6

Oxidative deamination and trans animation reactions involving glutamate

Question 7

What is positive nitrogen balance

Answer 7

Intake of nitrogen into body is greater than the loss of nitrogen from the body

Question 8

What is negative nitrogen balance

Answer 8

Amount of nitrogen excreted from body is greater than amount of nitrogen ingested

Question 9

How is nitrogen transported from plasma to liver

Answer 9

Glutamine - nitrogen from turned over body proteins
Alanine - from skeletal muscle

Question 10

Describe the formation of urea

Answer 10

In liver, nitrogen used to form water-soluble, non-toxic urea through urea cycle for excretion

Question 11

What is the fate of the carbon of catabolised body proteins

Answer 11

Form intermediates of glycolysis, gluconeogenesis, CAC or lipid metabolism pathways

Question 12

What are glucogenic and ketogenic carbons

Answer 12

Glucogenic - carbons from amino acid that can be converted to glucose
Ketogenic - carbons from amino acids that can be degraded to acetyl CoA