Enzymes

Question 1

What are enzymes?

Answer 1

proteins that act as biological catalysts to increase the rate of reaction by lowering the activation energy of the reaction.

Question 2

How do enzymes work?

Answer 2

One area of the enzyme is called the active site, which is specific to a certain substrate. The enzyme and substrate bind, forming an enzyme substrate-complex which lasts until the reaction is complete.

Question 3

What is meant by specific active site?

Answer 3

The 3D structure of each enzyme is unique due to the side chain and branches that are present. This also makes the active site unique, therefore only the substrates that match each active site can bind here.

Question 4

Activation energy

Answer 4

The minimum amount of energy needed to start a chemical reaction, by increasing the frequency of particle collisions.

Question 5

why is it necessary to measure the initial rate of reaction when investigating the effect of enzyme concentration on the rate of reaction.

Answer 5

There should be enough substrate molecules to ensure that the substrate is not a limiting factor, because substrate concentration decreases as the reaction progresses (it is used by enzyme). The speed of reaction in an enzyme controlled reaction is very fast and substrate concentration should be constant in each tests to ensure validity and accuracy so initial rate of reaction must be used.

Question 6

Rate of reaction: enzyme concentration

Answer 6

The rate of reaction increases as enzyme concentration increases as there are more active sites for substrates to bind to. However, increasing the enzyme concentration beyond a certain point has no effect on the rate of reaction as there are more active sites that substrates so substrate concentrations becomes limiting factor (graph would plateau)

Question 7

Rate of reaction: Substrate concentration

Answer 7

As substrate concentration increases, rate of reaction increases as more enzyme- substrate complexes are formed. However, beyond a certain point, the rate of reaction no longer increases as there are more substrates than active sites so enzyme concentration becomes the limiting factor.

Question 8

Rate of reaction: temperature

Answer 8

As temperature increases, rate of reaction increases up to the optimum temperature which is the temperature that the enzymes work best at. Rate of reaction decreases beyond the optimum temperature because enzymes denature.

Question 9

Rate of reaction: pH

Answer 9

Enzymes work within a narrow range of optimum (specific) pH value, values above or below this can alter the bonds within the structure, hence the shape of its active site.

Question 10

Enzyme structure

Answer 10

• globular protein
• active site a specific shape due to bonds between the R groups of the amino acids.