B3. ATP

Question 1

Adenosine triphosphate (ATP)

How do plant and animals cells release energy?
What is ATP made from?

Figure 1: The structure of ATP

Where is in the energy from ATP actually coming from and what does it do?

Answer 1

Plant and animal cells release energy from glucose-this process is called respiration. A cell can’t get its energy directly from glucose. So, in respiration, the energy released from glucose is used to make ATP (adenosine triphosphate). ATP is made from the nucleotide base adenine, combined with a ribose sugar and three phosphate groups (see Figure 1). It’s what’s known as a nucleotide derivative because it’s a modified form of a nucleotide.

Once made, ATP diffuses to the part of the cell that needs energy. The energy in ATP is stored in high energy bonds between the phosphate groups. It’s released via hydrolysis reactions

Question 2

Making and using ATP

Breakdown of ATP?

Figure 2: The breakdown of ATP - a hydrolysis reaction

Answer 2

When energy is needed by a cell, ATP is broken down into ADP (adenosine diphosphate) and P, (inorganic phosphate). This is a hydrolysis reaction. A phosphate bond is broken and energy is released. The reaction is catalysed by the enzyme ATP hydrolase

Question 3

Making and using ATP

Coupled…?

What is phosphorylation?

Resynthesis of ATP?

Figure 3: The synthesis of ATP - a condensation reaction.

Answer 3

ATP hydrolysis can be ‘coupled to other energy-requiring reactions in the cell - this means the energy released can be used directly to make the coupled reaction happen, rather than being lost as heat.
The released inorganic phosphate can also be put to use-it can be added to another compound (this is known as phosphorylation), which often makes the compound more reactive.
ATP can be resynthesised in a condensation reaction between ADP and P. This happens during both respiration and photosynthesis, and is catalysed by the enzyme ATP synthase