the aerobic system

Question 1

when is the aerobic energy system used?

Answer 1

exercise intensity is low
oxygen supply is high
e.g. jogging

Question 2

what does the aerobic system do?

Answer 2

breaks down glucose into carbon dioxide and water
in the presence of oxygen = much more efficient

Question 3

how many moles of ATP can the complete oxidisation of oxygen produce?

Answer 3

38 moles of ATP

Question 4

what happens to fats in the form of fatty acids?

Answer 4

they can be broken down

Question 5

what happens to proteins in the form of amino acids?

Answer 5

they can be broken down

Question 6

what do the products of fat and protein metabolism get reduced to?

Answer 6

the molecule acetyl coenzyme A

Question 7

where does acetyl coenzyme A enter?

Answer 7

the Krebs cycle

Question 8

what are the 3 stages of the aerobic system?

Answer 8

1) glycolysis
2) Krebs cycle
3) electron transport chain

Question 9

1) glycolysis:

Answer 9

• this stage is anaerobic
  -takes place in the sarcoplasm of muscle cell
  -the breakdown of glucose to pyruvic acid
  -for every molecule of glucose undergoing glycolysis, 2 molecules of ATP is formed

Question 10

what happens to pyruvic acid before it can enter the next stage? (Krebs cycle)

Answer 10

it is oxidised into two acetyl groups and carried to Krebs cycle by coenzyme A

Question 11

2) Krebs cycle

Answer 11

-the 2 acetyl groups diffuse into mitochondria
-complex cycle of reactions occur in a process (Krebs cycle)
-acetyl groups combine with oxaloacetic acid - forms citric acid
-rearranged form of citric acid undergoes ‘oxidative carboxylation’ (carbon and hydrogen given off)
-the carbon forms carbon dioxide
-CO2 transported to the lungs & exhaled out
-hydrogen taken to electron transport chain
-reactions create 2 ATP molecules

Question 12

3) electron transport chain

Answer 12

-hydrogen carried here by hydrogen carriers
-occurs in cristae of mitochondria
-hydrogen splits into hydrogen ions & electrons
-hydrogen ions & electrons charged with potential energy
-hydrogen ions oxidised to form water
-hydrogen electrons provide energy to re-synthesise ATP
-34 ATP formed during process

Question 13

what is beta oxidation?

Answer 13

-stored fat broken down into glycerol & free fatty acids for transportation by blood
-the fatty acids undergo beta oxidation
-they are converted into acetyl coenzyme A
-coenzyme A = entry molecule for Krebs cycle
-from here fat metabolism follows same path as glycogen metabolism
-more ATP can be made from one fatty acid molecule than one glucose molecule
-during long duration/low intensity exercise fatty acids will be main energy source
-dependant on fitness of performer

Question 14

advantages of aerobic system:

Answer 14

1) more ATP can be produced (34 ATP)
2) no fatiguing by-products (CO2 & water)
3) lots of glycogen & triglyceride stores - exercise can last longer

Question 15

disadvantages of aerobic system:

Answer 15

1) complicated system so can’t be used straight away
2) takes a while for oxygen to become available to meet demands of activity & make sure glycogen/fatty acids are completely broken down
3) fatty acid transportation to muscles is low & requires 15% more oxygen to be broken down than glycogen