iGCSE Biology 2c: Enzymes

What is the specific region on an enzyme that allows the substrate to bind?

• The active domain

• The catalytic center

• The active site

• The binding pocket

What is the primary structure of most enzymes composed of?

• Carbohydrates

• Proteins

• Lipids

• Nucleic acids

What is the reason for the drop in enzyme activity at temperatures above the optimum?

• The activation energy increases

• The substrate concentration decreases

• The enzymes denature

• The pH changes

Why do extremes of pH cause a drop in enzyme activity?

• They increase the activation energy

• They decrease the concentration of substrates

• They can denature the enzyme

• They change the temperature

Which of the following reactions do enzymes NOT catalyze?

• Metabolic reactions (changing molecules)

• Anabolic reactions (building molecules)

• Catabolic reactions (breaking molecules)

• Fission reactions

How does the active site of an enzyme facilitate the reaction?

• By providing additional reactants

• By increasing the activation energy

• By being complimentary to the substrate

• By changing the pH

How do enzymes provide an alternate reaction pathway?

• By increasing the number of reactant molecules

• By creating a new set of reactants

• By lowering the activation energy barrier

• By increasing the concentration of products

What is the term for the extra energy needed to break bonds within reactants to form products?

• Activation force

• Transition state energy

• Activation energy

• Reaction energy

What is the key function of enzymes?

• To increase the rate of chemical reactions

• To act as biological catalysts

• To be consumed in chemical reactions

• To lower the activation energy of reactions

How do enzymes catalyse substrates?

• By increasing the temperature

• By changing the pH

• By binding to the active site

• By providing additional energy