1. Unit 2 2.2 Cellular Respiration
Higher Biology
Unit 2
2.2 Cellular Respiration

2. Energy Release Respiration of glucose is a catabolic pathway.
It occurs in the cells of all members of the three domains of life.
It releases the energy stored in food.
This energy is used to make the high energy molecule ATP.

3. Energy release
ATP acts as the link between catabolic (energy releasing) reactions and anabolic (energy producing) reactions.
e.g. from respiration to protein synthesis.

4. Energy release
The function of ATP is to transfer chemical energy from catabolic to anabolic reactions.

5. Structure of ATP
A molecule of adenosine triphosphate (ATP) is composed of adenosine and three inorganic phosphates (Pi).
Adenosine Pi Pi Pi

6. Structure of ATP
The energy held in ATP is released when the terminal bond is broken by the action of enzymes.
Bond breaks
Adenosine Pi Pi Pi E

7. Structure of ATP
This results in the formation of adenosine diphosphate (ADP) and inorganic phosphate.
Adenosine Pi Pi + Pi

8. Phosphorylation
ATP can be regenerated from ADP and Pi in a reaction called phosphorylation.
Phosphorylation is an enzyme-controlled reaction when phosphate is added to a molecule.
Energy and the enzyme ATP synthase are required for phosphorylation.
Energy stored
ADP + Pi ATP
Energy released

9. Phosphorylation
The quantity of ATP in a cell at any given time should be fairly constant. This is because ATP is manufactured at the same time as it is used up. Therefore, there is no need for a living organism to possess a vast store of ATP. There is a rapid turnover of ATP in a cell.

10. Use of Energy Energy transferred by ATP from
catabolic reactions is used for;
Muscle contraction
Protein synthesis
Transmission of nerve impulses
Active transport
Cell division