Enzymes (Cambridge (CIE) AS Biology): Revision Note
Exam code: 9700
Enzymes as proteins
Enzymes are biological catalysts
‘Biological’ because they function in living systems
‘Catalysts’ because they speed up the rate of chemical reactions without being used up or changed
Enzymes are also globular proteins
Critical to the enzyme's function is the active site where the substrate binds
Metabolic pathways are controlled by enzymes in a biochemical cascade of reactions
Virtually every metabolic reaction within living organisms is catalysed by an enzyme – enzymes are therefore essential for life to exist
Enzymes can be intracellular or extracellular referring to whether they are active inside or outside the cell respectively
Intracellular enzymes are produced and function inside the cell
Extracellular enzymes are secreted by cells and catalyse reactions outside cells (e.g. digestive enzymes in the gut)
| Intracellular | Extracellular |
|---|---|---|
Example | Catalase | Amylase |
Function | Hydrogen peroxide is produced as a by-product of many cellular reactions It is harmful to cells Catalase converts hydrogen peroxide into water and oxygen, preventing cell damage | Digestion of food is carried out by extracellular enzymes This is because macromolecules of food are too large to enter cells Amylase is an an example of a digestive enzyme It digests carbohydrates into simple sugars |
Examiner Tips and Tricks
Don't forget that enzymes are proteins and so anything that could denature a protein, rendering it non-operational (extremes of heat, temperature, pH etc.) would also denature an enzyme.
Unlock more, it's free!
Did this page help you?
