4.2- Factors Affecting Enzyme Activity

Question 1

Explain the effect of temperature on enzyme activity.

Answer 1

temperature increases= particles have more kinetic energy= more frequent successful collisions= increase in the rate of reaction.
However, temperatures that are too high cause enzymes to denature:
High temps= bonds vibrate more= bonds strain + break = change in tertiary structure = enzyme denatures .
When an enzyme denatures, the active site changes shape, therefore substrate is unable to bind to it.

Question 2

What is the temperature coefficient?

Answer 2

Q10 is a measure of how much the rate of reaction increases with a 10C rise in temp.
For enzyme controlled reactions = usually 2.
Meaning Rate doubles with 10C increase.

Question 3

What is optimum temperature?

Answer 3

The temperature at which an enzyme has the highest rate of activity.
-varies differently in different organism types.
- optimum temp of enzymes in humans = 40*C
Once the enzymes have denatured above the optimum temp, the decrease in rate is very rapid.
- Q10 no longer applies once enzymes have denatured.
- the decrease in rate below the optimum temperature is not as rapid as enzymes haven’t denatured, they are just less active.

Question 4

What are the features of enzymes in different environments?

Answer 4

Cold:
-more flexible (especially active site)
-less stable than enzymes at higher temperatures. (Due to flexibility)
- small temperature change denatures them.
Hot: (thermophiles)
- more stable due the the increased no. of bonds in tertiary structures. (More hydrogen bonds and sulfur bridges)
-shapes are more resistant to change as the temperature rises.

Question 5

Explain the effects of pH on enzymes activity.

Answer 5

• change in pH =change in hydrogen ion concentration.
• Hydrogen ions interact with polar and charged R-groups. Changing the conc causes a change in the degree of interaction.
• Low pH (acid) =more hydrogen ions present = R-groups interact less = bonds break = enzyme changes shape.
• High pH (alkali)=fewer hydrogen ions present = R-groups interact more = bonds made= enzyme changes shape.

Enzymes only function within a narrow pH range. A significant pH change causes the enzyme to denature therefore decreasing rate of reaction

Question 6

What is optimum pH and renaturation?

Answer 6

• the active site will only be in the right shape at a certain hydrogen ion concentration. This is at the optimum pH.
• renaturation= if the pH returns to the optimum, the protein will resume its normal shape and catalyse the reaction again.

Question 7

What is the effect of substrate and enzyme concentration on rate of reaction?

Answer 7

Increase in substrate molecules in a certain volume= increase in collision rate
with enzyme active sites= more enzyme-substrate complexes= increase in rate.

Increase in enzyme conc= increase in collision rate = more enzyme-substrate complexes formed= increase in rate.

Question 8

When does rate increase to Vmax?

Answer 8

When all active sites are occupied so more complexes cant be formed until products are released.
The only way to increase rate would be to add more enzyme or increase temperature.