IGCSE Enzymes

Which statement is true about enzymes?

• The enzyme's active site protects the shape of the substrate

• Enzymes are used up in biological reactions

• Enzymes work faster at higher temperatures

• Every enzyme has one specific substrate that it breaks down or builds up.

Which of the following factors would not affect the rate of an enzyme-controlled reaction?

• Temperature

• pH

• Concentration of enzyme

• Concentration of product

• Concentration of substrate

The graph shows the effect of temperature on an enzyme. Which statement explains the trend from 10-70^oC?

• As temperature increases, enzyme activity increases

• 70^oC is the optimum temperature for this enzyme

• As temperature increases, enzymes become denatured.

• As temperature increases, enzyme activity decreases.

• As temperature increases, molecules gain more kinetic energy and have more successful collisions

What does the term optimum mean for enzyme temperature? Select the best description.

• The lowest temperature at which the enzyme works to form enzyme-substrate complexes

• The temperature which gives the highest enzyme activity forming the maximum number of enzyme-substrate complexes

• The highest temperature before denaturing occurs

Which of these statements about enzymes is true?

• Temperature does not affect their activity

• They can't be reused

• They lower the activation energy of a reaction

Which statement about the optimum pH for an enzyme is correct?

• It is the pH at which the enzyme's activity is greatest with the maximum number of enzyme-substrate complexes being formed

• It is the same for all enzymes

• It is the pH at which the enzyme cannot be damaged by heat

What is the purpose  of an enzyme?

• give permission for the reaction
• raise activation energy
• speed up reactions
• control how many reactions occur

Each enzyme only has 1 substrate that will fit its active site.  What is this called?

• reusable
• catalyst
• specific
• fragile

In the diagram, what is letter A? 

• product
• substrate
• enzyme-substrate complex
• active site

Letter D...

• active site
• enzyme
• substrate
• products