L6th summer mock exam quiz

The primary function of enzymes in biological systems is to:

• Provide structural support

• Store genetic information

• Speed up chemical reactions

• Transport oxygen

The structural nature of enzymes is:

• Carbohydrates

• Lipids

• Proteins

• Nucleic acids

Enzymes reduce the activation energy of reactions by:

• Increasing the temperature of the reaction

• Providing an alternative reaction pathway with lower activation energy

• Decreasing the concentration of reactants

• Changing the products of the reaction

The induced fit model of enzyme-substrate interaction suggests that:

• The enzyme's active site changes shape to fit the substrate upon binding.

• The enzyme's active site is rigid and does not change shape.

• The substrate changes shape to fit the enzyme's active site, which remains unchanged.

• The enzyme and substrate do not interact specifically.

Temperature affects the rate of enzyme-controlled reactions by:

• Increasing the rate up to an optimum, then decreasing it at higher temperatures

• Decreasing the rate continuously as temperature increases

• Having no effect on the rate

• Always denaturing the enzyme regardless of temperature

The impact of pH on enzyme activity is:

• It has no effect on enzyme activity.

• It can increase or decrease enzyme activity depending on the enzyme.

• It always increases enzyme activity.

• It always decreases enzyme activity.

The relationship between substrate concentration and enzyme activity is that as substrate concentration increases, enzyme activity:

• decreases steadily

• increases and then levels off

• remains constant

• decreases and then increases

How does enzyme concentration affect reaction rate?

• Increasing enzyme concentration increases reaction rate up to a certain point.

• Increasing enzyme concentration decreases reaction rate.

• Enzyme concentration has no effect on reaction rate.

• Enzyme concentration stops the reaction completely.

Differentiate between competitive and non-competitive inhibitors.

• Competitive inhibitors bind to the active site of the enzyme, blocking substrates from binding. Non-competitive inhibitors bind to a different site on the enzyme, causing a conformational change that alters the shape of the active site.

• Competitive inhibitors bind to a different site on the enzyme, while non-competitive inhibitors bind to the active site.

• Both competitive and non-competitive inhibitors bind to the active site of the enzyme.

• Non-competitive inhibitors increase the enzyme's activity, while competitive inhibitors decrease it.

How is the rate of reaction calculated, and what is the significance of the initial rate?

• The rate of reaction is calculated as the change in concentration of products or substrates over time. The initial rate represents the rate of reaction at the start when substrate concentration is highest, providing insights into the fastest possible reaction rate.

• The rate of reaction is calculated as the total amount of substrate present at the end of the reaction. The initial rate shows the slowest phase of the reaction.

• The rate of reaction is calculated by measuring the temperature change during the reaction. The initial rate is not significant in reaction studies.

• The rate of reaction is calculated as the change in pressure of the system. The initial rate represents the equilibrium state of the reaction.