1. The triathlon is an athletic event that involves performers undertaking a long distance swim, immediately followed by a cycle race and then finally a run of several kilometres.
(a) What would be the major energy sources used by a triathlete?
(3 marks)
(b) Briefly explain how these energy sources are used for regeneration of ATP.
(5 marks)

2. 2 (a) 1. Fats;
2. Fatty acids;
3. Glycerol;
4. Triglycerides.
Sub max 2 marks
5. Carbohydrates;
6. Glycogen;
7. Glucose;
8. Protein/lactate Sub max 2 marks
3 marks

3. (b) 1. Carbohydrates/glycogen/glucose broken down into pyruvate;
2. Anaerobic/glycolysis;
3. Some ATP produced;
4. Fats/triglycerides/fatty acids/glycerol broken down into variety of
compounds;
5. Beta oxidation;
6. Into mitochondria;
7. Krebs cycle;
8. Electron transport chain;
9. Oxidation/aerobic;
10. Large quantities of ATP produced.
5 marks

4. What happens when we need energy quickly?

5. Anaerobic Respiration
Describe how ATP is produced in the ATP-PC, and Lactic Acid systems
Give advantages and drawbacks of these systems.

6. 4c Molecule

7. Anaerobic Respiration
Does not require the presence of oxygen!
There are two types of anaerobic respiration:
ATP-PC system (alactic system)
Lactic Acid (Lactate anaerobic) system O2 O2 O2

8. Quick Recap – what happens in Glycolysis?
Lactic Acid System
Quick Recap – what happens in Glycolysis?

9. Glyco = Glucose Lysis = Splitting
Glycolysis
Glyco = Glucose Lysis = Splitting
Occurs in the cytoplasm
Glucose is converted into Glucose–6–Phosphate
Enzyme involved = PFK (phosphofructokinase)
Glucose–6–Phosphate is oxidised by the removal of 2 H2 molecules
Glucose-6-Phosphate is split into 2 molecules of Pyruvate
Energy is released and used to form 2 x ATP molecules

10. Lactic Acid System
The Lactic Acid system is essentially the process of glycolysis.
Occurs in the cell cytoplasm,
Glucose is split into 2 x pyruvate molecules
2x ATP molecules are produced
In aerobic respiration the pyruvate is then converted into Acetyl Co A by pyruvate dehydrogenase, and this enters Krebs Cycle.

11. When exercise intensity is high, oxygen supply to the muscles does not meet the demands for energy production.
With insufficient oxygen, not all the pyruvate can enter Krebs Cycle, so some builds up in the cytoplasm
If too much puruvate builds up, the process of glycolysis will stop and no more ATP will be produced.
Instead, the enzyme lactate dehydrogenase converts the pyruvate to lactic acid
This keeps glycolysis going so that 2x ATP can still be produced for each glucose broken down.

12. 4c Molecule

13. Lactic Acid System Advantages
Much faster to release energy than aerobic respiration
Does not require oxygen so can occur during very high intensity exercise
Any lactic acid produced can be converted back into glycogen and stored, or into pyruvate and used for aerobic respiration once exercise has finished
Produced 2 ATP per glucose
Muscles ability to buffer changes in pH can be improved by training

14. Lactic Acid System Disadvantages
Lactic acid accumulates which lowers the pH of the muscle cell and blood, and can prevent glycolytic enzymes working
Due to lactic acid build up, the muscles will fatigue within 1-3 mins
Only releases 2 ATP compared to the 38 released by aerobic respiration – only 5% of the energy in each glucose can be harnessed.

15. Remember though before all this takes place we are able to able to obtain energy for short bursts (1-10 seconds) through the……………………………………………

16. ATP-PC (alactic) System
Phosphocreatine (PCr) is an energy-rich compound found in cells.
The breakdown of PCr releases enough energy to resynthesise 1 ATP
Occurs in cell cytoplasm
Enzyme involved = creatine kinase
Muscles can contain stores of PCr sufficient to sustain around 10seconds of maximal exercise
There is some evidence that creatine supplements can increase muscle PCr stores.

17. ATP-PC (alactic) System Advantages
Very quick to provide energy to resynthesise ATP (almost immediate)
Can sustain 10s intense exercise
No fatiguing by-products produced
PCr stores are recovered by aerobic respiration very quickly after exercise finishes (within 2-3 mins)
Anaerobic – does not rely on oxygen supply
PCr levels can be improved by training and supplementation

18. ATP-PC System Disadvantages
Only lasts for 8-10s
When PCr stores depleted they cannot be replenished until after exercise finishes, or if exercise intensity drops significantly (as high levels of O2 availability are required for aerobic respiration) – fatigue occurs.
If exercise continues after the depletion of the PCr stores then other energy systems must be used to resynthesise ATP.
Only 1 ATP resynthesised for every PCr broken down.
Creatine supplementation has limited success, and potential side effects of cramps, bloating and dehydration.

19. The Energy Continuum
The energy systems are not used one at a time – all three are continually being used together, but depending on the activity some may be used more than others.
The factors that determine the predominant system:
Availability of oxygen
Exercise intensity
How soon energy is required

20. The relationship between the 3 systems can be shown graphically:
Aerobic
Time
10s
1 min
3 mins
ATP-PC
Lactic Acid
% Energy Supplied
ATP-PC-LA Threshold
LA-O2 Threshold

21. Activities lasting over 3mins
Activities can be plotted along an energy continuum line to show the predominant energy systems being used:
Activities lasting
2-10s
Activities lasting over 3mins
Anaerobic
Aerobic
ATP
ATP - PC
Activities lasting
10s-3mins
Activities lasting
1-3s

22. Exam Questions:
Elite swimmers can complete a 200 metres free-style race in just under 2 minutes.
(a) (i) Describe how the majority of energy will be produced for this type of race.
(4 marks)
(ii) Explain the main cause of muscle fatigue during this type of race.
(2 marks)

23. One popular form of training for Rugby Union is intermittent or interval training. This involves periods of intense exercise broken up with periods of rest.
The graph shows levels of ATP-PC stores during a period of interval training. The player sprints 50 metres and then walks back to the start of the sprint to recover before repeating the sprint.
(b) Use the graph to describe and explain the effects of interval training on
ATP-PC levels.
(4 marks)