Enzymes

Question 1

what are enzymes?

Answer 1

proteins that function as biological catalysts

Question 2

what is a catalyst?

Answer 2

substances that speed up a chemical reaction without being changed by the reaction.

Question 3

what does the lock and key hypothesis state? and what does this make enzymes?

Answer 3

the shape of the active site matches the shape of its substrate molecules.

This makes enzymes highly specific.

Question 4

what can each type of enzyme do?

Answer 4

Each type of enzyme can usually catalyse only one type of reaction

Question 5

describe the three stages that occur during the lock and key hypothesis:

Answer 5

1- substrate collides with active site of enzyme and becomes attached
2-enzyme catalyses breakdown/ synthesis of substrate
3-products released from active site

Question 6

what does each active site have?

Answer 6

a complementary shape to the substrate

Question 7

what could change the shape of the active site?

Answer 7

extremes of pH or high temperatures

Question 8

what is the effect of denaturing on substrates?

Answer 8

active site changes thereby the substrate will no longer fit the enzymes

Question 9

what is denaturing?

Answer 9

when the shape of the active site changes

Question 10

how could the rate of an enzyme-catalysed reaction be calculated? (2)

Answer 10

• measuring the rate at which a substrate is used up or

- the rate at which a product is formed.

Question 11

equation for rate of reaction:

Answer 11

amount of substrate used or amount of product formed/ time taken

Question 12

which three factors effect reaction rate?

Answer 12

• temperature
• substrate concentration
• pH

Question 13

describe the relationship between rate of enzyme activity and TEMPERATURE (4)

Answer 13

• as temperature increases, so does the rate of enzyme activity.
• optimum activity reached at enzyme’s optimum temperature.
• continued increase in temperature results in sharp decrease in activity as enzyme’s active site changes shape.
• It is now denatured and can no longer function.

Question 14

in relation to pH, what does each enzyme work best at?

Answer 14

a specific pH value

Question 15

describe the relationship between rate of enzyme activity and pH (4)

Answer 15

• as pH increases, so does rate of enzyme activity
• optimum activity is reached at the enzyme’s optimum pH
• continued increase in pH results in sharp decrease in activity
• as enzyme’s active site changes shape. It is now denatured.

Question 16

describe the relationship between rate of enzyme activity and substrate concentration (4)

Answer 16

• as substrate concentration increases, so does rate of enzyme activity.
• optimum rate is reached at the enzyme’s optimum substrate concentration.
• continued increase in substrate concentration results in the same activity
• enzymes are saturated as there are not enough enzyme molecules available to break down the excess substrate molecules.