Topic 18: Fuels

Question 1

Describe the oxidation of fatty acids for ATP production

Answer 1

Fatty acids chains are oxidised to produce 2-carbon acetic chain molecules which react with enzyme CoA to produce acetyl CoA entering the Krebs cycle.

Question 2

What happens when triglycerides get oxidised?

Answer 2

When triglycerides get oxidised, lots of acetyl CoA is created exceeding the utilization rate, so there will be excess acetyl CoA. The excessive actyle CoA will be used to produce ketone bodies through an anabolic process.

Question 3

Describe the oxidation of amino acids

Answer 3

Amino acids contain nitrogenous group (NH2) which will be reduced to make NH3 repackaged into urea to be removed by our kidneys.

The non-nitrogenous group can be oxidised ketone bodies or pyruvate that can be used in Krebs cycle.

Question 4

Distinguish the metabolic pathways when oxygen is present and absent

Answer 4

• When oxygen is present:
  + Main: oxidative phospholyration - turning glucose into ATP
  + Fatty acid: oxidised to make acetyl CoA
  + Amino acids: oxidised to make ketone bodies and pyruvate
  reduced to make NH3
  + Lactic acid: turned into pyruvate
• When oxygen is absent:
  + Only glycolysis happens
  + Fermentation: pyruvate is used to make lactic acid and help produce NAD+ by oxidizing NADH
  + Amino acids: oxidized to make pyruvate

Question 5

Describe the differences in prefernces for metabolic substrates between skeletal muscle, heart muscle, and brain, and the implications for these in starvation

Answer 5

• Skeletal muscle prefers using fatty acids, some glucose and ketone bodies.
• Heart muscle prefers using fatty acids, some lactate and ketone bodies
• Brain depends mostly on glucose and some ketone bodies

During fasting, tissues reduce their use of glucose, so the brain can utilize the glucose from liver.
During starvation, other tissues stop using glucose, so the fatty acids will be utilized by the liver to make ketone bodies for the brain to use.
Also, the muscles may be broken down into amino acids to be utilized by the liver to make glucose for the brain.

Question 6

Outline the major uses of energy in humans

Answer 6

Energy is used mainly for cellular activity including but not limited to contractility and motility (eg. muscles), ion pumping, signaling, bio synthesis (DNA, proteins, etc.)

Question 7

What happens if ATP is not continously produced?

Answer 7

The heart uses up a really large amount of ATP, but it doesn’t have a very high storage capacity. So, as soon as ATP production is prohibited, the heart can run out of ATP in 10s