Enzymes
What are Enzymes?
Biological catalysts – chemicals that speed up the rate of a reaction and remain
unchanged and reusable at the end of the reaction
Lower the activation energy of chemical reactions by influencing bond stability
Lower activation energy creates an unstable transition state in the substrate from which
the reaction proceeds steadily
Lower activation energy allows metabolic reactions to occur at body temperature
The number of reactions an enzyme can catalyse per second is known as the turn-over
rate
Enzymes are globular proteins with hydrophobic R groups on the outside, making them
water-soluble
They have a specific, 3D tertiary structure
The active site of an enzyme is an indented area with a shape that is specific to the
complementary substrate molecule
Intracellular Enzymes Extracellular Enzymes
Performs its function within the cell Performs its function outside of the cell
that produces it that produces it
Metabolic Pathways
A series of consecutive reactions that are each catalysed by a specific enzyme and result
in a specific product
Various reactants and intermediates act as substrates for specific enzymes
These reactants, intermediates and products are called metabolites
In catabolic pathways, metabolites are broken down into smaller ones and release
energy
In anabolic pathways, energy is used to synthesise larger metabolites from smaller one
What are Enzymes?
Biological catalysts – chemicals that speed up the rate of a reaction and remain
unchanged and reusable at the end of the reaction
Lower the activation energy of chemical reactions by influencing bond stability
Lower activation energy creates an unstable transition state in the substrate from which
the reaction proceeds steadily
Lower activation energy allows metabolic reactions to occur at body temperature
The number of reactions an enzyme can catalyse per second is known as the turn-over
rate
Enzymes are globular proteins with hydrophobic R groups on the outside, making them
water-soluble
They have a specific, 3D tertiary structure
The active site of an enzyme is an indented area with a shape that is specific to the
complementary substrate molecule
Intracellular Enzymes Extracellular Enzymes
Performs its function within the cell Performs its function outside of the cell
that produces it that produces it
Metabolic Pathways
A series of consecutive reactions that are each catalysed by a specific enzyme and result
in a specific product
Various reactants and intermediates act as substrates for specific enzymes
These reactants, intermediates and products are called metabolites
In catabolic pathways, metabolites are broken down into smaller ones and release
energy
In anabolic pathways, energy is used to synthesise larger metabolites from smaller one
