Week 9 Overview& Metabolism

Question 1

RECAP: CATABOLISM, ANABOLISM, METABOLISM

Answer 1

-Catabolism is breaking down complex compounds into simpler ones.
• Anabolism is building complex compounds from simpler ones.
• Metabolism is catabolism and anabolism combined.

Question 2

PROTEIN TURNOVER

Answer 2

Proteins are turned over in the body all the time: old ones are broken down, new ones are made.
300-500 g per day of protein turnover in healthy individuals.
Protein isn’t stored in the body – if it isn’t used it’s broken down.

Ill or athletes require a higher protien intake to recover the body as protien isn’t stored in the body

Question 3

THE AMINO ACID POOL

Question 4

DIETARY PROTEIN IS BROKEN DOWN DURING DIGESTION

Answer 4

Into stomach
HCL= pH 2 = proteins get denaturated
Got stretched out into long thread = shorter strands in the end = single amino acids
Pepsin = bigger chunks

Pancreas = trypsin, chrontrypsin, elastase, carboxypeptidases

Question 5

DIVIDING UP AMINO ACID MOLECULES

Answer 5

Ammonia
NH3 (ammonia gas) NH4+ (ammonium ion)
Source of nitrogen

Carbon skeleton
α-keto acids (different kinds – depends on the side chain)
Source of energy

Question 6

FATES OF AMINO ACIDS

Answer 6

Excess amino groups Excreted via urea

Whole molecule: Building blocks for nitrogenous compounds

Carbon skeleton
Converted into metabolic intermediates:
• Acetyl-CoA
• Acetoacetyl-CoA
• Pyruvate
• Krebs cycle intermediates

Question 7

AMINO GROUP CATABOLISM

Answer 7

Most amino acids metabolised in liver.
Some ammonia generated is recycled, the rest is excreted via urea (in most mammals).

Excess ammonia generated in other tissues travels to liver (as amino acids) to be metabolised.

Key amino acids in NH4+ metabolism:
Glutamine
Glutamate
Alanine Aspartate

Question 8

CARBON SKELETON CATABOLISM

Answer 8

Carbon skeletons enter the citric acid cycle via different intermediates:
• α-Ketoglutarate
• Succinyl-CoA
• Fumarate
• Oxaloacetate
• Pyruvate
• Acetyl-CoA

Glucogenic
AA’s that can be converted into glucose
Most amino acids

Ketogenic
AA’s that can only be converted into acetyl-CoA/ acetoacetyl-CoA
Exclusively lysine & leucine

Question 9

AMINO ACIDS ARE CLASSED AS ESSENTIAL OR NONESSENTIAL

Answer 9

Essential amino acids cannot be synthesised by the body so must always be provided by the diet.

Conditionally essential amino acids can be synthesised by the body but must be provided by the diet in certain circumstances.
(Stress,high training loads)
Nonessential amino acids can be synthesised by the body even under stress.

Note: the body only synthesises limited amounts of nonessential amino acids, it is better to have them in the diet too.