Exploring Enzymes and Metabolism

Which of the following best describes the role of enzymes in chemical reactions?

• Enzymes increase the activation energy required for a reaction.

• Enzymes decrease the activation energy required for a reaction.

• Enzymes are consumed in the reaction.

• Enzymes change the equilibrium position of the reaction.

Answer explanation

Enzymes act as catalysts by lowering the activation energy needed for chemical reactions, which speeds up the reaction without being consumed or altering the equilibrium position.

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DOK Level 2: Skill/Concept

What is the effect of temperature on enzyme activity?

• Enzyme activity decreases with increasing temperature indefinitely.

• Enzyme activity increases with temperature until an optimal point, then decreases.

• Enzyme activity is unaffected by temperature changes.

• Enzyme activity increases with decreasing temperature.

Answer explanation

Enzyme activity typically increases with temperature up to an optimal point, where the enzyme's structure is most efficient. Beyond this point, high temperatures can denature the enzyme, leading to decreased activity.

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DOK Level 2: Skill/Concept

Which graph best represents the relationship between substrate concentration and reaction rate in enzyme kinetics?

• A linear increase.

• A hyperbolic curve leveling off at high substrate concentrations.

• A parabolic curve.

• A constant line.

Answer explanation

The correct choice is a hyperbolic curve leveling off at high substrate concentrations, reflecting that as substrate increases, the reaction rate approaches a maximum due to enzyme saturation.

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DOK Level 2: Skill/Concept

How do competitive inhibitors affect enzyme activity?

• They bind to the active site, preventing substrate binding.

• They bind to an allosteric site, changing the enzyme's shape.

• They increase the enzyme's affinity for the substrate.

• They permanently deactivate the enzyme.

Answer explanation

Competitive inhibitors bind to the active site of an enzyme, blocking substrate access and preventing the reaction from occurring. This directly reduces enzyme activity, making the correct choice the first option.

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DOK Level 2: Skill/Concept

In metabolism, what is the primary role of enzymes?

• To store energy in the form of ATP.

• To act as catalysts and speed up biochemical reactions.

• To break down toxins in the body.

• To transport molecules across cell membranes.

Answer explanation

Enzymes primarily act as catalysts, speeding up biochemical reactions without being consumed in the process. This is essential for metabolism, as it allows reactions to occur at rates necessary for life.

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DOK Level 2: Skill/Concept

Which of the following statements about exothermic reactions is true?

• They absorb heat from the surroundings.

• They release heat to the surroundings.

• They require a constant input of energy to proceed.

• They have a higher activation energy than endothermic reactions.

Answer explanation

Exothermic reactions release heat to the surroundings, resulting in a temperature increase in the environment. This distinguishes them from endothermic reactions, which absorb heat.

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DOK Level 2: Skill/Concept

What is the role of enzymes in industrial applications?

• Enzymes are used to slow down chemical reactions.

• Enzymes are used to increase the yield and efficiency of processes.

• Enzymes are used to increase the cost of production.

• Enzymes are used to decrease the shelf life of products.

Answer explanation

Enzymes play a crucial role in industrial applications by increasing the yield and efficiency of processes, making them more cost-effective and sustainable. They catalyze reactions, speeding up production without compromising quality.

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DOK Level 2: Skill/Concept

Which of the following factors does NOT affect enzyme activity?

• pH level

• Substrate concentration

• Enzyme concentration

• Color of the enzyme

Answer explanation

The color of the enzyme does not influence its activity. Enzyme activity is affected by factors like pH level, substrate concentration, and enzyme concentration, but color is irrelevant.

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DOK Level 2: Skill/Concept

What is the difference between catabolic and anabolic pathways?

• Catabolic pathways build complex molecules, while anabolic pathways break them down.

• Catabolic pathways release energy, while anabolic pathways consume energy.

• Catabolic pathways occur only in plants, while anabolic pathways occur only in animals.

• Catabolic pathways require enzymes, while anabolic pathways do not.

Answer explanation

Catabolic pathways break down complex molecules and release energy, while anabolic pathways build complex molecules and consume energy. Thus, the correct choice highlights the energy dynamics of these metabolic processes.

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DOK Level 2: Skill/Concept

Enzymes will make a reaction go _______ and use ______ energy.

• faster, less

• faster, more

• slower, less

• slower, more

Answer explanation

Enzymes act as catalysts, increasing the rate of reactions (making them go faster) while lowering the activation energy required. Thus, the correct answer is 'faster, less'.