1 - Energy Transfer In The Body

Question 1

Define Adenosine Triphosphate (ATP)?

Answer 1

ATP is the only usable form of chemical energy in the body.

Question 2

Explain the role of ATPase?

Answer 2

ATPase breaks down ATP to produce ADP and Pi.

• Enzymes are used to break down compounds, ATPase is an enzyme that is used to break down ATP leaving adenosine due-phosphate (ADP) and an inorganic phosphate (Pi).

Question 3

We can resynthesises ATP from three different types of chemical reactions in the muscle cells. What are the three energy systems?

Answer 3

1) The Aerobic System
2) The ATP-PC System
3) The Anaerobic Glycolytic System

Question 4

Name the 3 stages of the aerobic system (how it works to provide energy?)

Answer 4

1) Glycolysis
2) Krebs Cycle
3) Electron Transport Chain

Question 5

Explain the First Stage of the aerobic system (how it works to provide energy?)

Answer 5

• Glycolysis
• The first stage is anaerobic so it takes place in the sarcoplasm of the muscle cell.
• For every molecule of glucose undergoing glycolysis, a net of two molecules of ATP is formed.
• Before the pyruvic acid produced in glycolysis can enter the next stage, it is oxidised into two acetyl groups and is then carried into stage two by coenzyme A.

Question 6

Explain the Second Stage of the aerobic system (how it works to provide energy?)

Answer 6

• Krebs Cycle
• The two acetyl groups diffuse into the matrix of the mitochondria and a complex cycle of reactions occurs in a process known as the Krebs cycle.
• The acetyl groups combine with oxaloacetic acid, forming citric acid.
• Hydrogen is removed from the citric acid and the rearranged form of citric acid undergoes ‘oxidative carboxylation’ which simply means that carbon and hydrogen are given off.
• The carbon forms carbon dioxide which is transported to the lungs and breathed out and the hydrogen is taken to the electron transport chain.
• The reactions that occur result in the production of two ATP molecules.

Question 7

Explain the Third Stage of the aerobic system (how it works to provide energy?)

Answer 7

• Electron Transport Chain
• Hydrogen is carried to the electron transport chain by hydrogen carriers.
• This occurs in the cristae of the mitochondria and the hydrogen splits into hydrogen ions and electrons and they are charged with potential energy.
• The hydrogen ions are oxidised to form water while the hydrogen electrons provide the energy to re-synthesise ATP.
• Throughout this process 34 ATP are formed.

Question 8

What is the memory tool for the aerobic system and how it works to provide energy?

Answer 8

GKE (Get Kinetic Energy)

G (Glycolysis)
K (Krebs Cycle)
E (Electron Transport Chain)

Question 9

Define Glycolysis?

Answer 9

A process in which glucose is converted to pyruvate to produce energy.

Question 10

Define the Sarcoplasm?

Answer 10

The fluid that surrounds the nucleus of a muscle fibre and is the site where anaerobic respiration takes place.

Question 11

Explain Beta Oxidation?

Answer 11

• Stored fat is broken down into glycerol and free fatty acids for transportation by the blood.
• These fatty acids then undergo a process called beta oxidation whereby they are converted into acetyl coenzyme A, which is the entry molecule for the Krebs Cycle.
• From this point on, fat metabolism follows the same path as glycogen metabolism.
• More ATP can be made from one molecule of fatty acids than one molecule of glucose, which is why in long duration, low-intensity exercise, fatty acids will be the predominant energy source but this does depend on the fitness of the performer.

Question 12

Name advantages of the aerobic system?

Answer 12

• More ATP can be produced: 36 ATP.
• There are no fatiguing by-products (carbon dioxide and water).
• Lots of glycogen and triglyceride stores so exercise can last for a long time.

Question 13

Name disadvantages of the Aerobic System?

Answer 13

• This is a complicated system so cannot be used straight away. It takes awhile for enough oxygen to become available to meet the demands of the activity and ensure glycogen and fatty acids are completely broken down.
• Fatty acid transportation to muscles is low and also requires 15% more oxygen to be broken down than glycogen.

Question 14

Define Phosphocreatine?

Answer 14

PC is an energy rich phosphate compound found in the sarcoplasm of the muscles which can be broken down quickly and easily to release energy to re-synthesise ATP.

Question 15

Define the ATP-PC system?

Answer 15

• This is an energy system that uses phosphocreatine as its fuel.
• It’s rapid availability is important for a single maximal movement such as a long jump take off or shot putt.
• This system only has enough PC to last around 5-8 seconds and can only be replenished during low intensity work when oxygen is available.
• E.g Usain Bolt running the 100m. He does not run the 100m with PC as his only energy source. He slows down for the last 20m as his stores of PC run out and he has to use a slower method of producing energy.

Question 16

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

Answer 16

• The ATP- PC system is an anaerobic process and re-synthesises ATP when the enzyme creating kinase detects high levels of ADP.
• It breaks down the PC in the muscles to phosphate and creatine, releasing energy:
  PC —> Phosphate (Pi) + Creatine (C) + Energy
• This energy is then used to convert ADP to ATP in a coupled reaction:
  Energy —> + Pi + ADP —> ATP
• For every molecule of PC broken down, there is enough energy released to create one molecule of ATP. This means the system is not very efficient but it does have the advantage of not producing fatiguing high by-products and it’s use is important in delaying the onset of anaerobic glycolysis system.

Question 17

Name advantages of the ATP-PC system?

Answer 17

• ATP can be re-synthesised rapidly using the ATP-PC system.
• PC stores can be re-synthesised quickly (30s = 50% replenishment and 3 mins = 100%)
• There are in fatiguing by-products.
• It is possible to extend the time the ATP-PC system can be utilised through use of creatine supplementation.

Question 18

Name disadvantages of the ATP-PC system?

Answer 18

• There is only a limited supply of PC in the muscle cell, ie it can only last for up to 10 seconds.
• Only one mole of ATP can be re-synthesised for every mole of PC.
• PC re-synthesis can only take place in the presence of oxygen (ie when the intensity of the exercise is reduced).

Question 19

Define the short-term lactate anaerobic system / Anaerobic Glycolytic System?

Answer 19

• The anaerobic glycolytic system provides energy for high-intensity activity for longer than the ATP-PC system.
• Working flat out to exhaustion will mean the system will last for a much shorter time. This is because the demand for energy is extremely high. At high intensity it can work for up to 45 seconds usually, however lower the intensity and it can last 2-3 minutes.
• The system re-synthesises ATP from the breakdown of the fuel glucose. This is supplied from the digestion of carbohydrates and is stored in the muscles and liver as glycogen.

Question 20

Explain how the anaerobic glycolytic system works to provide energy?

Answer 20

• When PC stores are low, the enzyme glycogen phosphorylase is activated to break down the glycogen into glucose, which is then further broken down to pyruvic acid by the enzyme phosphofructokinase. This process is called anaerobic glycolysis and takes place in the sarcoplasm of the muscle cell where oxygen is not available.
• Since this is an anaerobic process, the pyruvic acid is then further broken down into lactic acid by the enzyme lactate dehydrogenase (LDH).
• During anaerobic glycolysis, energy is released to allow ATP re-synthesis.
• The net result is two molecules of ATP are produced for one molecule of glucose broken down. (There is actually 4 moles of ATP produced but 2 are used to provide energy for glycolysis).

Question 21

Name advantages of the Anaerobic Glycolytic System?

Answer 21

• ATP can be re-synthesised quite quickly due to very few chemical reactions and lasts for longer than the ATP-PC system.
• In the presence of oxygen, lactic acid can be converted back into the liver glycogen or used as a fuel through oxidation until carbon dioxide and water.
• It can be used for a sprint finish (ie to use an extra burst of energy).