CH:3 - Enzymes

Question 1

Enzyme

Answer 1

A protein produced by a living organism that acts as a biological catalyst in a chemical reaction by reducing activation energy.

Question 2

Active Site

Answer 2

An area on an enzyme molecule where the substrate can bind.

Question 3

Lock-and-key hypothesis

Answer 3

A hypothesis for enzyme action; the substrate is a complementary shape to the active site of the enzyme, and fits exactly into the site; the enzyme shows specificity for the substrate.

Question 4

Induced-fit Hypothesis

Answer 4

A hypothesis for enzyme action; the substrate is a complementary shape to the active site of the enzyme, but not an exact fit – the enzyme, or sometimes the substrate, can change shape slightly to ensure a perfect fit, but it is still described as showing specificity.

Question 5

Activation Energy

Answer 5

The energy that must be provided to make a reaction take place; enzymes reduce the activation energy required for a substrate to change into a product.

Question 6

Colorimeter

Answer 6

An instrument that measures the colour of a solution by measuring the absorption of different wavelengths of light.

Question 7

V(max)

Answer 7

The theoretical maximum rate of an enzyme-controlled reaction, obtained when all the active sites of the enzyme are occupied.

Question 8

Michaelis–Menten constant (Km)

Answer 8

The substrate concentration at which an enzyme works at half.
Its maximum rate (½Vmax), used as a measure of the efficiency of an enzyme; the lower the value of Km, the more efficient the enzyme.

Question 9

Competitive Inhibitor

Answer 9

When a substance reduces the rate of activity of an enzyme by competing with the substrate molecules for the enzyme’s active site; increasing substrate concentration reduces the degree of inhibition; increasing inhibitor concentration increases the degree of inhibition.

Question 10

Non-competitive Inhibitor

Answer 10

When a substance reduces the rate of activity of an enzyme, but increasing the concentration of the substrate does not reduce the degree of inhibition; many non-competitive inhibitors bind to areas of the enzyme molecule other than the active site itself.

Question 11

Immobilised Enzymes

Answer 11

Enzymes that have been fixed to a surface or trapped inside beads of agar gel.