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What is photosynthesis? Use this GCSE OCR Science study guide to revise what type of reaction photosynthesis is, as well as factors affecting enzyme action and the effect of chlorophyll on photosynthesis.

For an organism to function, substances must move into and out of cells. Three processes contribute to this movement - diffusion, osmosis and active transport.

For an organism to function, substances must move into and out of cells. Three processes contribute to this movement – diffusion, osmosis and active transport.

Carbohydrates, proteins and lipids are required by humans. The digestive system breaks down large molecules. Nutrients are passed to other organisms in a food web. Enzymes are biological catalysts.

Plants compete for light, water, minerals and space. Animals compete for food, mates and territory. Decay is the breakdown of organic matter and is affected by temperature, water and oxygen.

The abundance of organisms in an ecosystem is dependent upon biotic (living) and abiotic (non-living) factors. Abundance and distribution are estimated using techniques such as transects and quadrats.