020 fuels for muscle contraction spl

Question 1

from this table, what does it tell you about the relationship between ATP and creatine phosphate?

Answer 1

• the conc of ATP has not changed despite the muscle contractions
• the concentration of creatine phosphate has dramatically decreased
• the creatine phosphate was phosphorylated, increasing the amount of creatine
• this suggests that the creatine phosphate was used up to maintain the ATP concentration

Question 2

how are glucose and oxygen uptake affected by exercise intensity and how might this change be mediated?

Answer 2

• the uptake of both oxygen and glucose increases with contraction intensity
• increased blood flow = increased glucose and oxygen uptake
• the increase in glucose uptake is further increased by the movement of GLUT4 to muscle cell membranes

Question 3

how is lactate output affected by exercise intensity?

Answer 3

• as the exercise intensity increases, the lactate output drops by a small amount, then greatly increases
• at rest the lactate is produced by anaerobic respiration of plasma glucose
• at low intensity exercise, the lactate may come almost completely from plasma glucose
• at high intensity exercise, the lactate may come partially from plasma glucose, but is also from muscle glycogen

Question 4

what are the limiting factors in the uptake of glucose?

Answer 4

• the number of glucose transporters on the plasma membranes
• the rate at which the liver can replenish the blood glucose

Question 5

what do these 2 graphs suggest about the relationship between muscle glycogen and the use of plasma fatty acids exercise continues?

Answer 5

• muscle glycogen greatly decreases over 105 mins, but the uptake of plasma glucose will not be substitute for the absence of glycogen
• over a much longer period of time, the muscle is still capable of increasing its uptake of plasma fatty acids
• as time passes, the use of fatty acids increases, which is necessary to make up for the decreasing glycogen stores

Question 6

how do you work out kJ/30 min of exercise?

Answer 6

litres of oxygen x kJ/L O2

Question 7

what is PAR and how do you work it out?

Answer 7

physical activity ratio = relative energy use
- divide current energy usage by rest energy usage

Question 8

how is muscle fuel choice affected by the intensity of the exercise?

Answer 8

• higher intensity exercise = more carbohydrates, less fat used

Question 9

why are carbohydrates and fats the most suitable for certain exercise intensities?

Answer 9

• anaerobic metabolism is not limited by oxygen supply
• at high exercise intensities, muscle glycogen is the only fuel that can be metabolised quickly enough to meet ATP demands
• muscle glycogen is limited, and is saved to some extent, for higher intensity exercises
• at low exercise intensities aerobic metabolism of mostly fat is sufficient to meet ATP demands
• the body fat stores are usually present far in excess of what would be required during a bout of exercise, so do not need to be preserved

Question 10

from this table, at which exercise intensity is the rate of fat oxidation the highest?

Answer 10

• 40%
• work out % of fat use in kj/30mins

Question 11

how do you think the figures would be different if the person was untrained?

Answer 11

• higher use of carbohydrates in both
• difference between fed and fasted would be smaller