Paper 1 & 2 Key Concepts - Enzymes

Question 1

Enzyme

Answer 1

A type of protein made up of amino acids.

Enzymes are biological catalists.

They speed up reactions but do not change it.

They have an active site which is where the substrate joins

Question 2

Substrate

Answer 2

The initial substance which an enzyme acts on

Question 3

Product

Answer 3

The substances that are made by they enzyme after the reaction

Question 4

Denature

Answer 4

The shape of the enzyme active site has changed and won’t fit any more.

Question 5

Active Site

Answer 5

The area where enzyme binds /attaches/ fit onto, to the substrate during a reaction

Question 6

Synthesis

Answer 6

where a sustance is produced from more than one substrate

Question 7

Digestion

Answer 7

The breaking down of substances into smaller products

Question 8

What does Optimum mean

Answer 8

The best or most appropriate - for instance, the conditions under which an enzyme works best (eg temperature and pH).

Question 9

Name three things that effect rate of Rate of Reaction

Answer 9

Temperature, PH, Substrate Concentration

Question 10

What is the lock and key mechanism

Answer 10

The substrate shape is complementary to the active site

Each active is specific to one enzyme

When an enzyme and substrate combine it becomes enzyme-substrate complex

When an active site is destroyed and changes shape i has become denatured

Question 11

Concentration

Answer 11

The concentration of a solution tells us how much of a substance is dissolved in water. The higher the concentration, the more particles of the substance are present.

Question 12

Catalyst

Answer 12

A substance that changes the rate of a chemical reaction without being changed by the reaction itself.

Question 13

Calculation for rate of reaction

Question 14

What affect does extremely high PH have on enymes?

Answer 14

Denatures them

Question 15

What dose the term optimum mean for enzyme temperature?

Answer 15

The temperature which gives the highest enzyme actiity

Question 16

What part of an enzyme makes it specific to a particular substrate?

Answer 16

Active Site

Question 17

Explain how temperature affects enzyme activity.

Answer 17

• At lower temperatures the molecules move more slowly so substrate molecules take long to fit into and react in the active site
• As the temperature increases so does the rate of enzyme activity (
  temperature increases kinetic energy - since the molecules are also moving faster, collisions between enzymes and substrates also increase)
• At the optimum temperature the enzyme is working at its fastest rate
• A continued increase in temperature results in a sharp decrease in activity as the enzyme’s active site changes shape. It is now denatured.

Question 18

How would you investigate the effect of PH n the rate of amylase activity?

Answer 18

• add amylase to starch solution in a test tube
• put tube in a water bath heated by a Bunsen burner for a constant temperature
• take samples of the mixture at regular intervals (eg every 10s) and mix them with a fresh drop of iodine on a dimple tile
• repeat the test until the iodine solution stops changing colour when the starch/amalysis mixture is added. Record the time taken for this to happen.
• Repeat the procedure at different PH values.

Question 19

Explain why enzymes have an optimum PH

Answer 19

If the PH is too high or too low it can interfere with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme

Question 20

What conditions can denature an enzyme?

Answer 20

High temperatures
Extreme (very high or low) PH

Question 21

Where are enymes of the digestive system produced?

Answer 21

carbohydrase enzymes are produced in the mouth, pancreas and small intestine

lipase enzymes are produced in the pancreas and small intestine

protease enzymes are produced in the stomach, pancreas and small intestine

Question 22

You have just completed a practical into the effects of temperature of the rate of an enzyme reaction. Describe the graph of results you would expect. [3 marks]

Answer 22

as the temperature increases so does the rate of reaction

this will continue until the optimum temperature is reached

at this point the enzyme’s rate of reaction is highest
further increases in temperature will reduce the rate of reaction

high temperatures will denature the enzyme and stop all reactions from occurring

Question 23

Describe the method you would investigate the effect of pH on enzyme activity. [6 marks]

Answer 23

Six from:

place a beaker of water on a Bunsen burner at about 35°C

put two drops of iodine solution into each spot of a spotting tile

add 2cm3 of amylase enzyme solution to a test tube

place 2cm3 of starch solution into the same tube

add 1cm3 of pH solution to the tube

mix the solution in the test tube and place it into the beak of water on the Bunsen burner

use a pipette to remove a few drops of solution every 20 seconds from the test tube and put them into a different well of the spotting tile
repeat until the iodine solution stops turning black

record the time this takes

repeat with different pH solutions

Question 24

Give two reasons why we have stomach acid

Question 25

Enzymes in the human liver have an optimum temperature of about 37 oC. Explain why our body temperature is controlled to stay about 37 0C

Answer 25

This means that enzymes are always at their optimum temperature so that reactions occur at the fastest rate.

Question 26

Reaction Rate calculation

Answer 26

1/time