Enzymes

Question 1

What is an enzyme?

Answer 1

A globular protein with a specific tertiary structure which catalyses metabolic reactions in living organisms.

Question 2

Where can enzymes be found?

Answer 2

They can be both intracellular an extracellular.

Question 3

What is the active site of an enzyme?

Answer 3

The area on an enzyme to which the specific substrate binds; other substrates will not bind.

Question 4

What is the lock and key hypothesis?

Answer 4

The theory in which an enzyme’s active site is complementary to the substrate molecule, like a lock and key.

Question 5

What is the induced fit hypothesis?

Answer 5

The theory an enzyme molecule changes shape to fit the substrate molecule more closely as it binds to it.

Question 6

What is an enzyme-substrate complex?

Answer 6

The intermediary formed when a substrate molecule binds to an enzyme.

Question 7

What is an enzyme-product complex?

Answer 7

The intermediate structure in which product molecules are bound to an enzyme molecule.

Question 8

How do enzymes speed up reactions?

Answer 8

Enzymes reduce the activation energy so the reaction can proceed at a much lower temperature.

Question 9

What is the effect of pH on enzymes?

Answer 9

At low pH the many H+ ions interfere with the H bonds by binding the amine group.
At high pH the OH- ions interfere with the H bonds by binding to the carboxyl group.
These both denature enzymes.

Question 10

What is the effect of low temperature on enzymes?

Answer 10

Reaction rate will be very slow because enzyme and substrate molecules have low kinetic energy.

Question 11

What is the effect of 40-50 degrees C on enzymes?

Answer 11

This is optimum temperature thus the enzymes will be at their most productive and reaction rate will be at its peak.

Question 12

What is the effect of high temperature on enzymes?

Answer 12

The kinetic energy of the molecules will be too high for the H bonds of the enzymes to withstand thus the bonds will break, the enzyme will denature.

Question 13

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

Answer 13

Increasing enzyme concentration will increase the rate of reaction until substrate concentration becomes a limiting factor and the reaction reaches its V max.

Question 14

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

Answer 14

Increasing substrate concentration will increase the rate of reaction until enzyme concentration becomes a limiting factor and the reaction reaches its V max.

Question 15

How would you test the effect of temperature on enzyme activity?

Answer 15

Sample potato tissue with a cork borer and cut into disks of equal thickness.
Equal amount of disks in a range of temps in water baths.
Pour equal of volumes of pH 7 buffer and hydrogen peroxide into different tubes and allow to equilibrate.
Add peroxide buffer mixture to each potato tube and fix a stopper and side arm.
Time how long it take oxygen bubble to move (oxygen is produce in reaction).

Question 16

How would you test the effect of pH on enzyme activity?

Answer 16

Mix a starch-agar solution and pour into pitri dish to form gel.
Cut wells into each plate and place the same volume of different pH buffer solutions bar control which is distilled water.
Incubate in a dry oven (35 degrees C for 24h).
Flood the plate and rinse with iodine measure the cleared zone- shows how much substrate turned to product.

Question 17

How would you test the effect of substrate concentration on enzyme activity?

Answer 17

As temperature but with equal temperatures and different volumes of hydrogen peroxide.

Question 18

How would you test the effect of enzyme concentration on enzyme activity?

Answer 18

As temperature but with equal temperatures and different numbers of potato disks in each tube.

Question 19

What is a competitive inhibitor?

Answer 19

A molecule that is similar in shape to the substrate and thus can fit into the active site temporarily, preventing enzyme substrate complexes from forming. Levels of inhibition depends on substrate concentration.

Question 20

What is a non competitive inhibitor?

Answer 20

A molecule that binds to an allosteric site, this denatures the tertiary structure of the enzyme permanently. Levels of inhibition depend inhibitor concentration.

Question 21

What is a cofactor?

Answer 21

An ion that binds to an enzyme and allows enzyme-substrate complexes to form more easily.

Question 22

What is a coenzyme?

Answer 22

A non protein organic molecule that binds temporarily to the active site and carry chemical groups between enzymes (taking part in the reaction).

Question 23

What is a prosthetic group?

Answer 23

A permanent coenzyme which contribute to the shape of the enzyme.

Question 24

Give a example of a metabolic poison.

Answer 24

Potassium Cyanide- binds to cytochrome oxidase and prevents aerobic respiration so kills through fatal lactic acid build up.

Question 25

Give an example of a coenzyme.

Answer 25

Vitamin B3- required for pyruvate dehydrogenase (involved in respiration) and used in the process of breaking down fats/carbs for energy.
B3 deficiency leads to a disease called pellagra.

Question 26

Give an example of a cofactor.

Answer 26

Chloride ions allow amylase to function properly (break down maltose molecules), without them the reactions will not take place.

Question 27

Give an example of a prosthetic group.

Answer 27

Carbonic anhydrase contains a zinc based prosthetic group where it is involved in catalysing the combination of water and CO2 to make carbonic acid which allows CO2 to be transported in the blood.