Factors Affecting Enzyme Activity: Enzyme Concentration, Denaturation and Buffers

Overview

Recall questions on Enzyme Concentration, Denaturation and Buffers.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is the effect of increasing enzyme concentration when substrate is in excess?

   Model answer

   The rate increases in direct proportion to the enzyme concentration, because more active sites are available for the substrate.

2. 2

   Why does increasing the enzyme concentration eventually fail to increase the rate any further?

   Model answer

   Substrate becomes the limiting factor, as there is not enough of it to occupy all the extra active sites.

3. 3

   Why does the rate of an enzyme-controlled reaction fall as the reaction proceeds, even at the optimum temperature?

   Model answer

   The substrate is gradually used up, so its concentration falls and successful collisions with active sites become less frequent.

4. 4

   Why is the initial rate of reaction measured rather than the rate later on?

   Model answer

   At the start the substrate concentration is at its known maximum and has not yet fallen, so the initial rate gives a fair comparison between different conditions.

5. 5

   How is the initial rate found from a graph of product formed against time?

   Model answer

   Draw a tangent to the curve at the origin and calculate its gradient.

6. 6

   State two ways in which the progress of an enzyme-controlled reaction can be followed.

   Model answer

   By measuring the rate at which a product appears, such as the volume of oxygen released by catalase, or the rate at which the substrate disappears, such as the loss of the blue-black colour when starch is digested by amylase.

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