Enzymes: Biology Edexcel: GCSE (9:1)

Enzyme

Biological catalysts which speed up reactions without being used up

Enzymes and temperature

The enzyme rate increases as temperature increases up to an optimum, after which the enzyme becomes denatured

Low temperatures and enzymes

Reduced chances of successful collision between enzymes and their complementary substrates

Effect of enzyme concentration

As enzyme concentration increases so will the rate of reaction, until saturation is reached

Enzymes and pH

The reaction rate decreases as the pH moves away from the enzyme's optimum pH

Optimum rate

An ideal pH or temperature value that results in maximum enzyme activity

Denature

When the active site irreversibly changes shape and can no longer bind to a substrate due to high temperature or unsuitable pH

Active site

The part of an enzyme where the substrate binds

Substrate

Reactant of an enzyme catalysed reaction

Product

A substance produced in a chemical reaction

Lock and key theory

When a substrate fits into its enzyme just like a key fits a lock

Amylase

A carbohydrase enzyme found in saliva and the small intestine that breaks the chemical bonds in starches

Protease

Enzyme found in the stomach and small intestine that breaks down proteins into amino acids

Lipase

Enzyme found in the small intestine that breaks down lipids into glycerol and fatty acids

Carbohydrases

Enzymes that speed up the breakdown of carbohydrates into simple sugars

Proteins

Building blocks of cells and tissues

Carbohydrates

Provide energy for chemical reactions

Lipids

Fats and oils which store energy

Inhibitors

Molecules that fit the active site of an enzyme but are not broken down, inhibitors reduce the rate of enzyme reactions