ATP

Question 1

What is ATP

Answer 1

ATP, or Adenosine Tri Phosphate, is an immediate source of energy for biological processes. Metabolic reactions in cells must have a constant, steady supply of ATP.
ATP contains three phosphate ions that play a significant role in energy transfer and this biological molecule is essential to metabolism, which is all the chemical reactions that take place in a cell.

Question 2

Explain the structure of ATP

Answer 2

ATP is comprised of:
Adenine, a nitrogenous base (meaning a base that contains nitrogen)
Ribose (a pentose sugar)
Three inorganic phosphate groups

Question 3

How is ATP an immediate source of energy

Answer 3

ATP is made during respiration from ADP, adenosine diphosphate, by the addition of an inorganic phosphate via a condensation reaction and using the enzyme ATP synthase.
ATP can be hydrolysed into ADP + Pi using enzyme ATP hydrolase.
ATP + water - ADP +Pi (energy)
By breaking one of the bonds between the inorganic phosphate groups in a hydrolysis reaction, a small amount of energy is released to the surroundings, which can be used in chemical reactions.
This is why ATP is an immediate energy source- only one bond has to be hydrolysed to release energy.
ATP can also transfer energy to different compounds. The inorganic phosphate released during the hydrolysis of ATP can be bonded onto different compounds to make them more reactive. This is known as phosphorylation, and this happens to glucose at the start of respiration to make it more reactive.

Question 4

What are the five properties of ATP

Answer 4

There are five key properties that ATP has making it a suitable immediate source of energy. In exam questions ATP properties are frequently compared to glucose, to emphasise why ATP is the immediate source of energy for cells rather than glucose. This is explained and demonstrated in the five points below.
I.ATP release energy in small, manageable amount so no energy is wasted.
This means that cells do not over heat from wasted heat energy and cells are less likely to run out of resources. In comparison to glucose, this would release large amounts of energy that could result in wasted energy,
2. It is small and soluble to easily transported around the cell.
ATP can move around the cytoplasm with ease to provide energy for chemical reactions within the cell. This is a property ATP has in common with glucose.
3. Only one bond is broken/hydrolysed to release energy, which is why energy release is immediate. Glucose would need several bonds to be broken down to release all its energy.
4. It can transfer energy to another molecule by transferring one of its phosphate groups.
ATP can enable phosphorylation, making other compounds more reactive. Glucose cannot do this, as it does not contain phosphate groups.
5.ATP can’t pass out of the cell, the cell always has an immediate supply of energy.
ATP cannot leave the cell, where as glucose can. This means that all cells have a constant supply of ATP or ADP Pi, but a cell can run out of glucose.