Enzymes：练习题

How do enzymes increase the rate of a chemical reaction?

A graph shows the effect of substrate concentration on the rate of an enzyme-catalysed reaction. At very high substrate concentrations, the curve reaches a plateau (\(V_{max}\)).
What is the limiting factor at the point where the curve levels off?

During an investigation into the induced-fit hypothesis, what is observed when a substrate molecule enters the active site of an enzyme?

Which statement correctly describes the structural nature of enzymes?

A solution containing an enzyme and its substrate was heated from \(30^\circ\text{C}\) to \(60^\circ\text{C}\). The rate of reaction increased initially but then fell to zero.
Which statement explains why the rate fell to zero at higher temperatures?

Define the term extracellular enzyme and provide one example of such an enzyme involved in the digestion of starch, as mentioned in the syllabus.

Distinguish between the lock-and-key hypothesis and the induced-fit hypothesis in terms of the flexibility of the enzyme's active site.

A researcher compares the activity of a free enzyme and an enzyme immobilised in alginate beads across a range of temperatures.
Explain why the immobilised enzyme typically shows a higher optimum temperature and remains active at temperatures that would denature the free enzyme.

Define the term enzyme and explain the structural and functional differences between intracellular and extracellular enzymes. Outline how enzymes increase the rate of metabolic reactions with reference to activation energy.

An investigation was conducted to study the effect of temperature on the rate of reaction of a protease enzyme. The reaction rate increased as the temperature was raised from \(10\,^{\circ}\text{C}\) to \(40\,^{\circ}\text{C}\), but then dropped sharply at temperatures above \(45\,^{\circ}\text{C}\).
(a) Explain the increase in reaction rate in terms of kinetic energy and collision theory.
(b) Describe and explain the effect of high temperatures on the tertiary structure<\/b> of the enzyme and its ability to catalyze reactions. <\/p>