1.1 Energy Systems Flashcards
Where does the energy used for muscle contractions come from?
Adenosine triphosphate (ATP)
What is ATP?
The only usable form of energy in the body. Consists of 1 molecule of adenosine and 3 phosphates
What are the 3 ways ATP can be re-synthesised?
Aerobic system
ATP-PC system
Anaerobic glycolytic system
When is the aerobic system used?
When exercise intensity is low and oxygen supply is high, eg; jogging.
What are the 3 stages of the aerobic system?
- Glycolysis
- Krebs cycle
- Electron transport chain
Define glycolysis
A process where glucose is converted to pyruvate to produce energy
What happens in the first stage (glycolysis)?
- 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.
Define Krebs cycle
A series of cyclical chemical reactions that take place using oxygen in the matrix of the mitochondrion
What happens during the second stage (Krebs cycle)?
- 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.
What happens during the third stage (electron transport chain)?
- 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.
What happens during beta oxidation?
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.
What are the advantages of the aerobic system?
- more ATP can be produced (34)
- no fatiguing by products
- exercise can last for longer as there’s lots of glycogen stores
What are the disadvantages of the aerobic system?
- takes a while for enough O2 to become available to meet the demands of the exercise.
- fatty acids transportation to muscles is low
How does the ATP-PC system work to provide energy?
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
Advantages of ATP-PC system?
- ATP can be re-synthesised rapidly
- Phosphocreatine stores can be re-synthesised quickly
- No fatiguing by products
Disadvantages of ATP-PC system
- Limited supply of phosphocreatine (only lasts for 10 secs).
- Only 1 mole of ATP can be re-synthesised for every mole of PC.
How does the anaerobic glycolytic system provide energy
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.
Where does anaerobic glycolysis occur?
In the sarcoplasm of the muscle cell where oxygen is not available.
When is the anaerobic glycolytic system used?
Provides energy for high intensity activities lasting up to 3 minutes, but can peak at 45 seconds. Eg; 400m sprint
Define VO2 max
The maximum volume of oxygen that can be taken up by the muscles per minute
What rate of oxygen do we consume at rest?
Consume at a rate of 0.3 - 04 litres per minute
What is the maximum oxygen consumption during exercise?
3 - 6 litres per minute (VO2 max)
Define sub maximal oxygen deficit
Where there’s not enough oxygen available at the start of exercise to provide all the energy aerobically.
Explain EPOC
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.
