1.1 Energy Systems

Question 1

Where does the energy used for muscle contractions come from?

Answer 1

Adenosine triphosphate (ATP)

Question 2

What is ATP?

Answer 2

The only usable form of energy in the body. Consists of 1 molecule of adenosine and 3 phosphates

Question 3

What are the 3 ways ATP can be re-synthesised?

Answer 3

Aerobic system
ATP-PC system
Anaerobic glycolytic system

Question 4

When is the aerobic system used?

Answer 4

When exercise intensity is low and oxygen supply is high, eg; jogging.

Question 5

What are the 3 stages of the aerobic system?

Answer 5

1. Glycolysis
2. Krebs cycle
3. Electron transport chain

Question 6

Define glycolysis

Answer 6

A process where glucose is converted to pyruvate to produce energy

Question 7

What happens in the first stage (glycolysis)?

Answer 7

• Takes place in the sarcoplasm of the muscle cell.
• For every molecule of glucose undergoing glycolysis, a net of 2 molecules of ATP is formed.
• Before the pyruvic acid produced in glycolysis can enter the next stage, its oxidised into 2 acetyl groups.
• Carried into Krebs cycle by coenzyme A.

Question 8

Define Krebs cycle

Answer 8

A series of cyclical chemical reactions that take place using oxygen in the matrix of the mitochondrion

Question 9

What happens during the second stage (Krebs cycle)?

Answer 9

• The 2 acetyl groups diffuse into the matrix of the mitochondria and a complete cycle of reactions occur.
• The acetyl groups combine with oxaloacetic acid, forming citric acid
• Hydrogen is removed from the citric acid, which is called oxidative carboxylation, meaning hydrogen and carbon are given off.
• The carbon forms CO2 which is breathed out, and the hydrogen is taken to the electron transport chain.

Question 10

What happens during the third stage (electron transport chain)?

Answer 10

• Hydrogen is carried to the electron transport chain.
• This occurs in the cristae of the mitochondria.
• The hydrogen splits into hydrogen ions and electrons, they’re charged with potential energy.
• The hydrogen ions are oxidised to form water.
• The hydrogen electrons provide the energy to re-synthesise ATP, and 34 ATP are formed.

Question 11

What happens during beta oxidation?

Answer 11

Stored fat is broken down into glycerol and free fatty acids for transportation by the blood. These fatty acids are converted into acetyl coenzyme A (beta oxidation).

ATP can be made from fatty acids which is why in long duration, low intensity exercise, they will be the predominant energy source.

Question 12

What are the advantages of the aerobic system?

Answer 12

• more ATP can be produced (34)
• no fatiguing by products
• exercise can last for longer as there’s lots of glycogen stores

Question 13

What are the disadvantages of the aerobic system?

Answer 13

• takes a while for enough O2 to become available to meet the demands of the exercise.
• fatty acids transportation to muscles is low

Question 14

How does the ATP-PC system work to provide energy?

Answer 14

It’s an anaerobic process and re-synthesises ATP when the enzyme creatine kinase detects high levels of ADP.

It breaks down the phosphocreatine in the muscles to phosphate and creatine, releasing energy.

This energy is used to convert ADP to ATP

Lasts for 5-8 seconds

Question 15

Advantages of ATP-PC system?

Answer 15

• ATP can be re-synthesised rapidly
• Phosphocreatine stores can be re-synthesised quickly
• No fatiguing by products

Question 16

Disadvantages of ATP-PC system

Answer 16

• Limited supply of phosphocreatine (only lasts for 10 secs).
• Only 1 mole of ATP can be re-synthesised for every mole of PC.

Question 17

How does the anaerobic glycolytic system provide energy

Answer 17

When PC stores are low, the enzyme glycogen phosphorylase is activated to break down glycogen into glucose.
This is then broken down into pyruvic acid by the enzyme phosphofructokinase.
The pyruvic acid is further broken down into lactic acid by the enzyme LDH.

Question 18

Where does anaerobic glycolysis occur?

Answer 18

In the sarcoplasm of the muscle cell where oxygen is not available.

Question 19

When is the anaerobic glycolytic system used?

Answer 19

Provides energy for high intensity activities lasting up to 3 minutes, but can peak at 45 seconds. Eg; 400m sprint

Question 20

Define VO2 max

Answer 20

The maximum volume of oxygen that can be taken up by the muscles per minute

Question 21

What rate of oxygen do we consume at rest?

Answer 21

Consume at a rate of 0.3 - 04 litres per minute

Question 22

What is the maximum oxygen consumption during exercise?

Answer 22

3 - 6 litres per minute (VO2 max)

Question 23

Define sub maximal oxygen deficit

Answer 23

Where there’s not enough oxygen available at the start of exercise to provide all the energy aerobically.

Question 24

Explain EPOC

Answer 24

Excess Post-exercise Oxygen Consumption

When a performer finishes exercise, O2 consumption still remains high because extra O2 needs to be taken in to aid recovery. This breathlessness is known as EPOC. There are 2 main components, fast and slow.

Question 25

What is the fast component of EPOC?

Answer 25

The restoration of ATP and phosphocreatine stores and the re-saturation of myoglobin with oxygen.