ADENOSINE TRIPHOSSPHATE Flashcards
Adenosine triphosphate (ATP)
is the chemical energy ‘currency’ of all body cells, including muscle cells. It powers all the cell’s metabolic activities, including, in the case of muscle cells, the ability to contract. An ATP molecule consists of adenosine and a chain of three inorganic phosphate groups bound together by high-energy chemical bonds.
The phosphate ‘tail’ of ATP is the actual ‘power source’ that the cell catabolises (breaks down).
- Available energy is contained in the bonds between the phosphates and is released when they are broken. Usually only the outer phosphate is removed from ATP to yield energy.
- When this occurs, ATP is converted to adenosine diphosphate (or ADP) and inorganic phosphate (or Pi — a free-floating phosphate molecule)
ATP formula
The energy released during the breakdown of ATP to ADP and Pi is used to power cell processes such as the mechanisms involved in muscular contraction. This can be represented by the formula:
ATP↔ADP + Pi + Energy.
ATP - important points
This system provides the fastest rate of ATP resynthesis as it uses the fuel creatine phosphate (CP) or phosphocreatine (PC) already stored in the muscle.
- This system has the fastest rate of ATP resynthesis, therefore is used as the predominant energy system by athletes competing in short duration, high-intensity ‘power’ events.
- This is the most powerful system, but has a limited capacity to generate ATP as it fatigues rapidly.
- This can only be used as the predominant energy system for up to 6 – 10 seconds. The first 2 – 3 seconds of maximal effort work will rely on the breakdown of existing ATP stores in the muscle.
REPLENISHING ATP STORES
While the breakdown of ATP is required in order to provide the energy that powers the mechanisms involved in muscular contraction, muscular stores of ATP are very limited. ATP lasts 1-2 seconds before it needs to be replenished
Phosphorylation: A biochemical process which adds a phosphate group to ADP to make ATP!!
ATP resynthesis with oxygen = aerobic metabolism
ATP resynthesis without oxygen = anaerobic metabolism
STEPS: (on how ATP replenishes)
- Bonds between the 3 phosphates contain energy
- Energy is released when one of the bonds is broken= ADP
- Through food the inorganic phosphate molecule can rejoin (ATP resynthesis)
- It is then broken again
FUEL SOURCES
The energy required to resynthesize ATP comes from the breakdown of the following fuels
Chemical fuel
Creatine Phosphate Chemical fuel containing a high-energy phosphate bond for the rapid release of energy
Limited storage of CP within the muscles
Carbohydrates Sugars and starches – bread, pasta, fruit, vegetables
The body’s preferred source of fuel under exercise conditions. Glycogen can provide the energy for ATP resynthesis under both anaerobic (no oxygen required) and aerobic (oxygen required) conditions.
Fats Fats are a concentrated fuel source in dairy products, oils, nuts and meat
Preferred fuel source at rest, and during prolonged submaximal exercise Fats (or lipids) are found in many different foods. They can be divided into:
- saturated fats
- unsaturated fats.
Protein Protein is found in meat, fish, eggs, legumes and grains
Used for muscle growth and repair
Minimal contribution to energy production during exercise
ATP resynthesis: demand, rate and yield
At all times, all three energy systems contribute to the resynthesis of ATP during physical activity. During any activity, ATP resynthesis (supply) must be able to meet the ATP demand of the activity. Two factors determine the ATP demand of an activity:
- exercise duration — how long the activity lasts for
- exercise intensity — how hard the exercise is performed (often measured using heart rate per minute).
