04. Enzymes (6093)

Enzymes speed up the rate of chemical reactions.

• True

• False

Answer explanation

Enzymes are biological catalysts that speed up the rate of chemical reactions.

Enzymes can be produced by the ribosomes in a cell.

• True

• False

Answer explanation

Enzymes are made from proteins. This means that enzymes can be broken down to form amino acids, and that enzymes are made by the ribosomes (as they make proteins).

Enzymes are chemically changed at the end of a reaction. Hence, only a small amount of enzymes are required for each reaction.

• True

• False

Answer explanation

Enzymes are only required in small amounts as they remain chemically unchanged at the end of a reaction.

This means that their specific 3D shape remains the same, and they are able to bind to another substrate molecule and catalyse the reaction.

Enzymes increase the activation energy of a chemical reaction.

• True

• False

Answer explanation

Enzymes decrease the activation energy of a chemical reaction. Hence, enzymes speed up the rate of chemical reactions.

All enzymes have an optimum temperature of around 35°C - 40°C.

• True

• False

Answer explanation

All enzymes have an optimum pH. However, their optimum pH is not standard, and depends on where the enzyme is supposed to function.

E.g., enzymes found in organisms that live in thermal vents have a much higher optimum temperature compared to enzymes found in humans.

Enzymes can bind with substrates that have a similar shape to its active site.

• True

• False

Answer explanation

Only substrates that are complementary in shape to the specific 3D shape of an enzyme's active site can bind and form an enzyme-substrate complex.

Based on the lock-and-key hypothesis, the enzyme is the lock and the substrate is the key.

• True

• False

Answer explanation

The enzyme is the lock that contains the active site (groove) for the substrate to fit in as the key.

At low temperatures, enzymes are inactive.

• True

• False

Answer explanation

At low temperatures, enzymes are inactive as the kinetic energy of enzyme molecules is low. The chances of enzyme-substrate complex formation is low.

Enzymes are denatured when they are placed in a solution with pH below their optimum pH.

• True

• False

Answer explanation

There are three conditions that can result in the denaturation of enzymes:

• - pH above optimum

• - pH below optimum

• - temperature above optimum

The optimum temperature of an enzyme represents the temperature at which the enzyme works the slowest.

• True

• False

Answer explanation

The optimum temperature of an enzyme represents the temperature at which the enzyme works the fastest.