enzymes

Catalyst

a substance that speeds up a reaction without changing the substances produced or being used up in the reaction

Enzyme

biological catalysts which control the rate of reactions that occur in individual cells and organisms

Enzyme structure

Globular proteins - the polypeptide chains are folded into spherical or globular shape
Hydrogen bonds, ionic bonds, disulphide brides and hydrophobic/hydrophilic interactions between R groups of amino acids maintain the specific 3D shape of the enzyme
Enzymes will only catalyse specific reactions or group of reactions and they are affected by changes in temperature and pH

Anabolic reactions

reactions that build up new chemicals

Catabolic reactions

reactions that break substances

Intracellular enzymes

enzymes that catalyse reactions inside the cells. Eg: DNA polymerase, DNA ligase

Extracellular enzymes

enzymes that catalyse reactions outside the cells. Eg: lysozyme

Activation energy

the minimum energy that the reactant molecules must possess in order to start a reaction

Active site

the area of the enzyme which has a specific shape, into which the substrate of a reaction fits

Substrate

the molecule or molecules on which the enzyme acts

How do enzymes work?

By lowering the activation energy needed for a reaction to take place. To lower the activation energy, they form a complex with the substrate of a reaction. Once the products of a reaction are made, they are released and the enzyme is free to form a new complex with more substrate

Lock and key hypothesis

the active site affects the bonds in the substrate by making it easier to break or making it easier for the bonds to break between them. the formation of the enzyme substrate complex lowers the activation energy of the reaction. once the reaction is completed the products are not in the right shape to stay in the active site and the complex breaks up. this releases the products and frees the enzyme for further catalytic activity

Induced fit hypothesis

the active site has a distinct shape and arrangement, but it is flexible. after the substrate enters the active site, the shape of that site changes around it to form the active complex. once the products have left the complex, the enzyme returns to its inactive relaxed form until another substrate molecule binds

explain how the primary structure of enzyme determines its three dimensional structure and properties

enzymes are globular proteins and they are soluble as they are made up of a high number of polar amino groups.
the sequence of amino acids is the primary structure of proteins.
the primary structure determines the positions of the bond to hold the protein structure.
these bonds include hydrogen bond, ionic bond, disulphide bond and R groups which are involved in chemical reactions.
Hydrophilic R groups are found on the outside of enzymes making enzymes soluble
The shape of the active site is determined by the position of amino acids
the shape of the active site is complimentary to the substrate so that it can bind to form the enzyme substrate complex
the shape of the active site of the enzymes determines that the enzyme is specific

Explains how the change of one amino acid can lead to a change in the structure and properties of the haemoglobin protein

when an amino acid is changed, there is a change in the primary structure.
there will be different R groups leading to the formation of different bonds.
these bonds include hydrogen bond, ionic bond and disulphide bond.
this results in a different secondary and tertiary structure.
due to this, haemoglobin may have different properties such as change in solubility, less affinity of oxygen, flexibility, etc.

factors affecting enzyme activity

Temperature, pH, enzyme concentration, enzyme specificity, substrate concentration