THE AEROBIC SYSTEM

Question 1

three stages

Answer 1

The three stages are known as:
1. Glycolysis
2. Kreb’s Cycle
3. Electron Transport Chain (ETC)

Question 2

the aerobic system

Answer 2

This system is the most complex and involves the greatest number of chemical reactions. It has three distinct stages and is able to use either carbohydrate (CHO) or lipids (fat) fuels stored inside and outside of the working muscles. The by-products formed as a result of using this system include CO2, H2O and heat.

This system has a considerably slower rate of ATP resynthesis due to a reduction in intensity, but has an unlimited capacity for resynthesis and is therefore the predominant energy system used at rest and during events lasting over 75 seconds.

Question 3

Comparing carbohydrate and fat metabolism

Answer 3

The aerobic system can produce ATP through either fats (fatty acids) or carbohydrates (glycogen). The key difference is that the breakdown of fats produces significantly more ATP (greater yield) compared with that obtained from an equivalent amount of carbohydrates.

Question 4

Aerobic energy production from proteins

Answer 4

Protein is thought to make only a small contribution (usually no more than 5–10 per cent) to energy production. However, amino acids, the building blocks of protein, can be either converted into glucose or into other intermediates used by the Krebs cycle such as acetyl coenzyme

Question 5

Carbohydrates are the preferred fuel source during exercise because:

Answer 5

• they can be metabolised aerobically or anaerobically
• they produce energy at a faster rate than fat
• the complete oxidation of carbohydrates requires less oxygen than the complete oxidation of fat
• carbohydrate stores are more readily accessible than fat stores (triglycerides have to be reduced to glycerol and free fatty acids before they can be used to generate cellular energy).

Question 6

Active recovery is suitable after aerobic type activities because it:

Answer 6

• maintains an elevated heart rate to increase blood flow to the working muscles
• provides a skeletal muscle pump to increase blood flow back to the heart
• decreases venous pooling
• assists with thermoregulation by slowly reducing core temperature
• accelerates the oxidation of metabolic by-products such as H+ ions that have accumulated in the muscle.

Question 7

exercise

Answer 7

Predominant system for long duration, low/submaximal intensity exercise.

Question 8

fuel source

Answer 8

Glycogen and triglycerides

Question 9

Rate of energy for ATP resynthesis

Answer 9

Slow
Glycogen 1.0 mol/min, triglycerides < 1.0 mol/min

Question 10

intensity

Answer 10

Submaximal intensity exercise
(70 - 85% MHR)
Resting/low intensity exercise
(> 70% MHR)

Question 11

Limiting factor (fatigue)

Answer 11

Fuel depletion (glycogen)
Thermoregulatory fatigue

Question 12

Amount of energy produced

Answer 12

Large yield
38 ATP per glycogen molecule
441 ATP per triglyceride (147 per FFA)

Question 13

duration

Answer 13

75+ seconds

Question 14

By-products

Answer 14

COz, H20, heat