Life relies on the continuous transfer of energy.

In this module you will cover:

• Photosynthesis - chlorophyll absorbs light energy, which is used to produce ATP.

• Respiration - various molecules act as respiratory substrates, and their hydrolysis is linked to ATP production.

In both processes, ATP is generated as protons diffuse down an electrochemical gradient through ATP synthase, an enzyme embedded in organelle membranes.

Photosynthesis occurs in all photoautotrophic organisms, while respiration is a universal process across all life forms, providing indirect evidence for evolution.

• Biomass - Most of the sugars synthesised by plants are used by the plant as respiratory substrates. The rest are used to make other groups of biological molecules. These biological molecules form the biomass of the plants. They are then consumed by animals, bacteria, and fungi. 

• Energy transfer in ecosystems - Both photosynthesis and respiration are not 100% efficient, and energy transfer through biomass in a food chain results in inefficiencies in energy transfer between trophic levels.

• Nutrient cycles - Nutrients are recycled within natural ecosystems, exemplified by the nitrogen cycle and the phosphorus cycle.