Energy Transfer In The Body Flashcards
What is ATP?
The only usable form of energy in the body.
What is ATP made of?
Energy from foods is broken down and is used to form ATP.
It’s 1 molecule of adenosine and 3 phosphates
How is energy released?
By breaking down the bonds that hold ATP together.
How is ATP broken down?
The enzyme ATP-ase
This leaves ADP - adenosine di-phosphate - and an inorganic phosphate (Pi).
How do we get ATP back?
The body has to constantly rebuild ATP by converting the ADP and Pi back into ATP.
We can re-synthesise ATP from 3 different types of chemical reaction in the muscle cells; these are fuelled by either food or a chemical called phosphocreatine
What are the energy systems?
Aerobic
ATP-PC
Anaerobic glycolytic
When is the aerobic system used?
When exercise intensity is low and oxygen supply is high (jogging), its the preferred energy pathway.
What are the stages of the aerobic system?
Glycolysis
Krebs cycle
Electron transport chain
What is glycolysis?
The breakdown of glucose into pyruvic acid.
What happens in glycolysis?
The first stage is anaerobic so it takes place in the sarcoplasm of the muscle cell.
For every molecule of glucose undergoing anaerobic glycolysis, a net of two molecules of ATP is formed.
What happens before the Krebs cycle?
Before the pyruvic acid produced in glycolysis can enter the next stage, it splits into two acetyl groups
It is then carried into the Krebs cycle by coenzyme A.
What is the Krebs cycle?
A series of chemical reactions that take place using oxygen in the matrix of the mitochondria.
What happens in the Krebs cycle?
Acetyl coenzyme A diffuses into the matrix of the mitochondria and a complex cycle of reactions occur
The acetyl coenzyme A combines with oxaloacetic acid, forming citric acid.
Hydrogen is removed from the citric acid and the rearranged form of citric acid undergoes oxidative carboxylation (carbon and hydrogen are given off).
The carbon forms carbon dioxide which is transported to the lungs and breathed out.
The hydrogen is taken to the electron transport chain.
The reaction produces 2 molecules of ATP.
What happens if fat enters the Krebs cycle?
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 1 mole of fatty acids than 1 mole 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.
What is beta-oxidation?
A process where fatty acids are broken down to generate acetyl-CoA, which enters the Krebs cycle.
What is the electron transport chain?
This involves a series of chemical reactions in the cristae of the mitochondria where hydrogen is oxidised to water and 34 molecules of ATP are produced.
What happens in the ETC?
Hydrogen is carried to the ETC by hydrogen carriers.
This occurs in the cristae of the mitochondria.
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 molecules of ATP are formed
How many moles of ATP are formed at each stage of the aerobic system?
Glycolysis - 2
Krebs - 2
ETC - 34
What is the sarcoplasm?
The fluid that surrounds the nucleus of a muscle fibre; the site where anaerobic respiration takes place.
What is the ATP-PC system?
An energy system using phosphocreatine (PC) as its fuel.
What is PC?
An energy rich phosphate compound found in the sarcoplasm of the muscles.
It can be broken down quickly and easily to release energy to re-synthesise ATP.
Its rapid availability is important for a single maximal movement, such as the long jump take-off or shot putt.
How does the ATP-PC system work?
It 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 then used to convert ADP to ATP in a coupled reaction.
What’s the equation for the ATP-PC system?
PC -> Pi + creatine + energy
Energy -> Pi + ADP -> ATP
What’s the anaerobic glycolytic system?
Provides energy for high-intensity activity for longer than the ATP-PC system
Why does the anaerobic glycolytic system vary?
Depends on the fitness of the individual and how high the intensity of the exercise is.
Working at an extremely high intensity will mean the system will last much shorter because the demand for energy is very high.
An elite athlete who has just run the 400m in under 45 seconds will not be able to run it again immediately at the same pace.
However, reduce the intensity a little and the system can last longer, up to 2-3 minutes, because the demand for energy is slightly lower.
How does the anaerobic glycolytic system work?
When the 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 the anaerobic glycolysis, energy is released to allow ATP re-synthesis.
The net result is 2 mole of ATP are produced for one molecule of glucose broken down (4 are produced but 2 are used to provide energy for glycolysis itself).
How many mole ATP are produced for each system?
Aerobic - 34
ATP-PC - 1
Anaerobic glycolytic system - 2
How long does each energy system last?
ATP-PC - 5/8 seconds
Anaerobic glycolytic system - 2/3 minutes
Aerobic - anything above
