Enzymes

Catalysts and Activation Energy

• A catalyst is a substance that speeds up the rate of a chemical reaction, it does this by decreasing the activation energy. Enzymes catalyse biochemical reactions.
• Activation Energy is the minimum energy needed by particles for a reaction to happen, this energy comes from the things that are involved in the reaction colliding, these are called reactants. If there is not enough energy in the collisions, a catalyst can be used to decrease the activation energy and increase the rate of reaction.

Substrate Molecules

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• The substrate is the molecule that the enzyme acts upon. Each enzyme is specific to one substrate molecule or type of molecule.
• The substrate molecules have to travel to the enzyme's active site and collide constantly.
• The lock and key hypothesis states that the active site specifically matches the shape of the substrate molecule

What Affects Enzyme Controlled Reactions

• For my GCSE course I need to know two things that affect enzyme controlled reactions they are Temperature and pH levels
• At low temperatures, there is less kinetic energy meaning that the substrate molecules will not collide as often.
• At optimum temperature (which is usually about 40°) the rate of reaction is at its highest point.
• At higher temperatures, the enzyme may change shape so the substrate molecules are unable to fit the active site, this is known as a denatured enzyme.
• With pH, a pH too far away from its optimum pH and the enzyme will become denatured.

Temperature

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• Caption: This is the rate of reaction at different temperatures

pH

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• Caption: This is the rate of reaction at different pH's

Digested Enzymes

• Digestive Enzymes are produced by specialised cells in glands and in the lining of the alimentary canal, these enzymes catalyse the breakdown of large insoluble molecules into smaller, soluble ones which can be absorbed through the small intestine wall to enter the bloodstream. Different parts of the digestive tract ave different pH conditions meaning that different enzymes work in different places.