Integration of Whole Body Metabolism

Question 1

Describe the fuel needed to sprint

Answer 1

ATP directly powers muscle contraction. Power and speed depends on ATP availability

Muscle ATP stores are small, rapid ATP release is largely anaerobic:
ATP stores like creatine phosphate
Glycolysis
Glycogenolysis

Question 2

Describe the mobilisation of ATP from creatine phosphate

Answer 2

Relatively small but rapidly mobilised ATP store lasting only a few seconds
The build up of lactate and the fall in pH ultimately limits performance

Question 3

Describe the fuel for a marathon

Answer 3

Uses more efficient aerobic resp so needs muscle, liver and adipose tissue co-operation
Initially glycogen is used but later fat is mobilised from the adipose tissue.
Fats are a large source of ATP, but metabolism is x10 slower than creatine phosphate
The result is approximately half of the glycogen stores remain

Question 4

Describe the interaction between liver and muscle during exercise

Answer 4

Lactate is exported from the muscle back to the liver where it can be converted by gluconeogenesis to glucose
during extreme exercise, hay protein breakdown which will form alanine

This alanine will then be transported back to the liver, where it can be converted to glucose again through gluconeogenesis.

Question 5

What happens during the post absorptive phase, several hours after the last meal?

Answer 5

blood glucose falls insulin levels fall and glucagon levels rise

Phosphorylase a activity increases, as does glycogen breakdown
Drop in insulin reduces glucose uptake by muscle and adipose tissue
slide 7

Question 6

What happens during early starvation (24hrs no food)?

Answer 6

Glucose released from the liver due to gluconeogenesis and glycogenolysis

FA mobilisation from adipose tissue is used for FA oxidation

Insulin drops causing GLUT4 expression by muscle to fall, reducing glucose uptake
Also hay an initial increase in protein breakdown

Question 7

What happens during intermediate starvation?

Answer 7

Glycogen stores depleted
Increased lipolysis and ketogenesis
Increased gluconeogenesis to maintain blood glucose
Further starvation sees the kidney take over gluconeogenesis from the liver

Question 8

What happens during prolonged starvation?

Answer 8

β-hydroxybutyrate plateauxs at 20 days
The brain starts to move to using ketone bodies, so glucose need falls to 40g/day
Lactate and glycerol are used in gluconeogenesis
Lactate is recycled by the Cori cycle. Glycerol and aas are oxidized
Proteins are broken down by the muscle forming aa precursors

Question 9

What is the main take home message of long term metabolism?

Answer 9

Basically Long term metabolism shifts from glucose to fats and eventually proteins