Worksheet: Enzyme Action

In this worksheet, we will practice describing the 'lock and key' theory of enzyme action.

Q1:

Fill in the blank: The reactant that an enzyme will bind to, due to its complementary shape, is a/an .

  • Aactive site
  • Bprotein
  • Ccatalyst
  • Dsubstrate
  • Eproduct

Q2:

Enzymes act as catalysts. What does a catalyst do?

  • AA catalyst speeds up the rate of a reaction.
  • BA catalyst increases the number of reactants in a reaction.
  • CA catalyst always maintains a constant rate of reaction.
  • DA catalyst ensures a reaction never ends.
  • EA catalyst slows down the rate of a reaction.

Q3:

Which of the following statements correctly defines an enzyme?

  • AAn enzyme is a product of digestion.
  • BAn enzyme is a molecule that has been broken down.
  • CAn enzyme is a biological catalyst.
  • DAn enzyme is an inorganic catalyst.
  • EAn enzyme is a fast reaction.

Q4:

Which of the following is not a reaction, or a type of reaction, that involves enzymes?

  • APhotosynthesis
  • BRespiration
  • CBreaking down large molecules into smaller ones
  • DDiffusion
  • ESynthesizing large molecules from smaller ones

Q5:

With reference to enzymes, what does “denatured” mean?

  • AThe enzyme’s active site has been irreversibly changed.
  • BThe enzyme has been killed.
  • CThe enzyme has been used as much as it can be and must be replaced.
  • DThe enzyme has been damaged and subsequently works more slowly.
  • EThe enzyme’s protein structure has been stretched.

Q6:

Which of the following best describes the lock and key theory of enzyme action?

  • AThe enzyme and substrate have identical shapes, like a “lock and key.”
  • BThe enzyme is the “lock” into which the substrate, or the “key,” fits.
  • COnce the enzyme and substrate have joined, they are locked together and cannot be separated.
  • DThe substrate is the “lock” into which the enzyme, or the “key,” fits.

Q7:

The enzyme in the diagram has had its active site irreversibly changed. What scientific term describes this change?

  • ADeformation
  • BDecomposition
  • CDenaturation
  • DDying
  • EDeposition

Q8:

A diagram of an enzyme and some substrates is shown. Which substrate will the enzyme bind to?

  • AZ
  • BX
  • CY
  • DV

Q9:

A diagram of an enzyme and some substrates is provided. Which substrate will the enzyme bind to?

  • AY
  • BX
  • CZ
  • DV

Q10:

The enzyme catalase catalyzes the reaction that breaks down hydrogen peroxide into water and oxygen. The table shows how much oxygen is produced over time when this reaction occurs with and without catalase.

In which reaction is the rate of oxygen production lower?

Volume of Gas Produced (cm3)
Time (s)Without CatalaseWith Catalase
000
20523
401135
601949
802565
1002870
1203270
1403670
  • AThe rate is the same in both reactions.
  • BThe rate is lower in the reaction with catalase.
  • CThe rate is lower in the reaction without catalase.

Q11:

In the diagram provided, a section is labeled with a ?. This is where the substrate will bind. What is the scientific term given to this part of the enzyme?

  • AEnzyme–substrate complex
  • BActive site
  • CTertiary site
  • DJoining site
  • EComplementary site

Q12:

Which of the following statements correctly links enzymes, substrates, and active sites?

  • AThe enzyme’s active site is constantly changing to have a complementary shape to a range of substrates.
  • BThe substrate has an active site that has a complementary shape to a range of enzymes.
  • CThe substrate has an active site that has an identical shape to a specific enzyme.
  • DThe enzyme has an active site that has an identical shape to a range of substrates.
  • EThe enzyme has an active site that has a complementary shape to a specific substrate.

Q13:

The diagram provided shows a basic outline of the lock and key theory.

Which letter represents the enzyme?

  • AZ
  • BX
  • CY
  • DNone

Which letter represents the substrate?

  • AZ
  • BX
  • CY
  • DNone

Which letter represents the products of this reaction?

  • AX
  • BZ
  • CY
  • DNone

Q14:

The diagram provided shows a basic outline of the lock and key theory.

Which label represents the substrate?

  • AY
  • BZ
  • CX
  • DNone

What has happened to the substrate?

  • AIt has been used to form a polymer.
  • BIt has been broken down.
  • CIt has been joined in a reaction.
  • DIt has been dissolved.

In which step has an enzyme–substrate complex formed?

Q15:

The enzyme catalase catalyzes the reaction that breaks down hydrogen peroxide into water and oxygen. The graph shows how much oxygen is produced over time when this reaction occurs with and without catalase.

Which of the following statements correctly describes the trend shown?

  • AThe reaction produces more oxygen when catalase is present.
  • BThe reaction produces more oxygen when catalase is not present.
  • CThe reaction produces oxygen at a quicker rate when catalase is present.
  • DThe reaction produces oxygen at a quicker rate when catalase is not present.
  • EThere is no correlation between the rate of oxygen production and the presence of catalase.

Q16:

A diagram of an enzyme and some substrates is shown. Which substrate will the enzyme bind to?

  • AV
  • BX
  • CY
  • DZ

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