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Photosynthesis and respiration:

The product that is made at the end of photosynthesis is glucose.

Respiration is the process by which all organisms release energy from food.

Plants respire only, at night adn give out Carbon Dioxide. During the day, they photosynthesise as well as respire. There will be a net output of oxygen.


Enzymes are chemicals that speed up the rate of chemical reactions.

They are proteins. They consist of long chains of amino acids joined together.

The chemicals that enzymes work on are called substrates.

The chemicals produced in the reaction are called products.

The order and types of amino acid in an enzyme give it a complicated three-dimensional shape. This shape is essential for the enzyme to work.

A part of the enzyme is called the active site, it has a special shape that the substrate fits into neatly.

The substrate molecules that are locked into the active site take part in the chemical reaction and product molecules are released.

Enzymes need a specific pH level and temperature to work at their optimum.

As the temperature is increased, enzyme activity increases because reaction rate increases.

High temperatures change the shape of the active site of the enzyme. At a point where the change in shape is permanent, the enzyme has been denatured.

The lock and key model of enzyme action:

1. Substrate molecules move towards active site in enzyme.

2. Substrate molecule fits in active site in enzyme.

3. Reaction occurs and products made; the enzyme speeds up the reaction.

4. Product molecules do not fit in the enzymes as well so are released. The enzyme can then be used again with new substrate molecules.

Glucose - making it and using it:

Sunlight is absorbed by the green chemical chlorophyll which, along with the enzymes for photosynthesis, is found in structures in the cell called chloroplasts.

Uses of glucose:

- Proteins for growth

- Cellulose for cell walls



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