B1.2.4 Enzyme Reactions

Question 1

List the factors that the rate of an enzyme catalysed reaction depends on

Answer 1

pH
Temp
Enzyme concentration
Substrate concentration

Question 2

How does temperature affect enzyme controlled reactions?

Answer 2

At higher temperature, the enzyme and substrate molecules move faster and collide more often
In general, the higher the temperature, the faster the reaction
However, if the temp becomes too high, the enzymes denature

Question 3

What happens when temperature is too high

Answer 3

The amino acid chains in the protein start to unravel, changing the shape of the
active site
Now the substrate can no longer bind and so the rate of reaction decreases
Once all the enzyme molecules are denatured, the reaction stops

Question 4

How does PH affect enzyme controlled reactions?

Answer 4

-every enzyme has an optimum PH
-if PH is too high or too low may make the enzyme unfold, changing the shape of the active site
-then enzyme is denatured

Question 5

Describe what happens when an enzyme is denatured. (5)

Answer 5

If the temperature becomes too high, the amino acid chains in the protein start to unravel, changing the shape of the active site.
The enzyme is now denatured.
The substrate can no longer bind and so the rate of reaction decreases.
Once all the enzyme molecules are denatured the reaction stops.
Most denatured enzymes cannot return to their original shape - the change is irreversible.

Question 6

Describe what happens when an enzyme is denatured. (5)

Answer 6

If the temperature becomes too high, the amino acid chains in the protein start to unravel, changing the shape of the active site.
The enzyme is now denatured.
The substrate can no longer bind and so the rate of reaction decreases.
Once all the enzyme molecules are denatured the reaction stops.
Most denatured enzymes cannot return to their original shape - the change is irreversible.

Question 7

Substrate concentration against rate of reaction (4)

Answer 7

In general, the higher the substrate concentration is, the faster the rate of reaction.
But at a certain substrate concentration, all the enzyme molecules are bound to substrate molecules.
The rate of the reaction is at its maximum.
Any further increase in the number of substrate molecules will not increase the rate of reaction as there are no enzymes for them to bind to

Question 8

Enzyme concentration against rate of reaction (3)

Answer 8

In general, the higher the enzyme concentration is, the faster the rate of reaction.
But this is limited by substrate concentration.
If no new substrate molecules are added the reaction will stop