3. Enzymes

Question 1

Define activation energy

Answer 1

Energy needed in a chemical reaction for a product to form

Question 2

(Q1) What is the activation energy of the reaction in the presence of the enzyme?

Answer 2

A

Question 3

(Q2)Which statement explains how the substrate is able to enter the active site of the enzyme?

Answer 3

Contact between the substrate and the enzyme causes a change in the enzyme shape.

Question 4

(3) why did the actual rate of reaction decrease over time?

Answer 4

Substrate molecules were used up

Question 5

(4) Catalase is an enzyme that catalyses the conversion of hydrogen peroxide into water and oxygen.
Two students investigated the effect of enzyme concentration on the rate of reaction of the
enzyme catalase. The students predicted their results would show the same trend. The graphs
show the rates obtained by each student.

Answer 5

Student 2 used a lower concentration of substrate in the investigation

can’t be temp bc that’s not what they’re studying and changing

can’t be pH bc that’s also kept constant

can’t be inhibitor bc that’s not what they’re studying

Question 6

What is an enzyme inhibitor?

Answer 6

Something that inhibits the rate of enzyme activity

Question 7

What is a competitive inhibitor?

Answer 7

It has a similar shape to the substrate and temporarily fits into the enzymes active site, competing with the substrate

Question 8

What can make a competitive inhibitor reversible?

Answer 8

Increasing the substrate concentration will reduce effect of inhibitor

Question 9

What is non-competitive inhibition? 2

Answer 9

It doesn’t bind to the active site, but another part of the enzyme

causing a change in the enzymes shape so it’s no longer complementary

Increasing substrate has no effect

Question 10

What level of protein structure is always involved in competitive and non-competitive inhibitors of enzymes?

Answer 10

tertiary

Question 11

How do you calculate mean?

Answer 11

Sum of terms divided by number of terms

Question 12

what is an enzyme-substrate complex?

Answer 12

a temporary molecule formed when the substrate binds to the enzyme

Question 13

(7) which graph shows the change in concentration of enzyme substrate complex?

Answer 13

A

not B bc not just concentration but CHANGE in concentration

Question 14

What is the lock and key hypothesis

Answer 14

Active site has perfectly complementary shape to substrate

Question 15

What is induced-fit hypothesis?

Answer 15

Active site, or sometimes substrate, can change shape slightly to fit together better for more efficient enzyme activity

Question 16

What do the lock and key and induced fit hypotheses have in common

Answer 16

Substrate is converted to product by specific R groups in the active site

Question 17

Lysozyme is secreted from tear glands & forms deposits in contact lenses. How would one clean this?

Answer 17

Protease dissolves lysozyme

Question 18

(13) Which graph statement is correct?

Answer 18

Between X & Y, the number of enzyme molecules is limiting

Question 19

What is involved in enzyme regulation? 3

Answer 19

Change in enzyme concentration

Change in substrate concentration

Inhibition by final product of reaction

Question 20

What type of bond is formed between an enzyme and a substrate?

Answer 20

Hydrogen bond

Question 21

How do you plot the initial rate of reaction? 3

Answer 21

draw a tangent to the curve at the start of the reaction

Find an easy- to read part of the scale to stop drawing

Make triangle as big as possible

Question 22

How do you calculate the initial rate of reaction? 2

Answer 22

Calculate the gradient of line

Change y / change x

Question 23

(18) which graph represents action of a non-competitive inhibitor?

Answer 23

A

Question 24

Which orders of protein structure control the shape of the active site

Answer 24

Primary, secondary, tertiary & quaternary

Question 25

(20) n an experiment, 5cm^3 of 1% salivary amylase is added to 100cm^3 of different concentrations of starch

Which graph shows the results of plotting the initial rate of reaction (y axis) against substrate concentration (x axis)

Answer 25

A