EnzymesEnzymesThe cell’s essential

molecules

The Importance of The Importance of EnzymesEnzymes

Enzymes are very special protein molecules found in the cytoplasm of cells

They speed up reactions in cells without the need for an increase in temperature !

Enzyme ActivityEnzyme Activity Enzymes are found in both animal and

plant cells where they speed up reactions. They can speed up reactions which break

down large molecules into small ones. They also build small molecules together

to produce larger more complex molecules.

An enzyme in

the cell’s

cytoplasm

splitting

a dangerous

substance into

two harmless

ones.

An Enzyme at WorkAn Enzyme at Work

Enzymes and TemperatureEnzymes and TemperatureEnzymes can only help reactions when they come

in contact with their substrates* (*substances which join to enzymes)

Molecules in a liquid move faster if they are given more energy by heating the liquid.

Enzymes and their substrates find each other faster in warm liquids.

Enzyme reactions are faster in warm liquids!

The graph below shows how enzyme reactions The graph below shows how enzyme reactions speed up when warm, but go slowly when cold!speed up when warm, but go slowly when cold!

14

12

10

8

6

4

2

0

Rate of reaction with Temperature

Volume ofOxygen produced (cms3)

Temperature °C

5 10 15 20 25 30 35

Enymes and Temperature Enymes and Temperature continuedcontinued

Write down the following temperatures in your jotters with a space between them. 10°C _____ 20°C ____ 30°C ______

Find out the volume of oxygen produced by the enzyme at each of these temperatures.

Your teacher will now take you back to the last slide.

The graph below shows how enzyme reactions The graph below shows how enzyme reactions speed up when warm, but go slowly when cold!speed up when warm, but go slowly when cold!

14

12

10

8

6

4

2

0

Rate of reaction with Temperature

Volume ofOxygen produced (cms3)

Temperature °C

5 10 15 20 25 30 35

Enzymes in DangerEnzymes in Danger• Enzymes are very complex protein molecules.

• Acids and alkalis also damage these complex molecules !

• If their shape is changed they can no longer work as enzymes !

• When they come in contact with very high temperatures they start to change shape.

Effects of Temperature and Effects of Temperature and Acids and AlkalisAcids and Alkalis

Enzyme before treatment - acomplex protein.

After heat or contact with acid the protein unravels and no longer functions as an enzyme!The enzyme is denatured.

More about Temperature and enzymesMore about Temperature and enzymesThe graph on the next slide shows the way in

which the activity of an enzyme changes with temperature. Try to answer the following questions about this graph in your jotter.

What is happening:—1. To the activity between points A and B2. To the activity at point B3. To the activity between points B and C4. To the enzyme between points B and C5. Think carefully - why was no measurement

made at 0°C ?

This graph shows what happens to they way an This graph shows what happens to they way an

enzyme reacts over a range of temperatures !enzyme reacts over a range of temperatures !

A

B

C

14

12

10

8

6

4

2

Rate of reaction with Temperature

Volume ofOxygen produced (cms 3 )

Temperature °C

5 10 15 20 25 30 350

40 45

16

Enzyme fact fileEnzyme fact fileCopy the title of this slide. Then copy and complete and the sentences below.

1. Enymes are protein molecules found in the …….?…. of cells.2. Enzymes ….?…. ..?. reactions inside cells.3. Enzymes can speed up reactions which:— ……?…. small molecules into larger ones. ……?…. …?… large molecules into small simple molecules.4. Reactions which use enzymes can be speeded up by ……?……. the ……?……. .5. Enzymes do not function when …..?….. by …..?…. temperatures.6. ….?…. and …..?….. also damage enzymes.

Word Bank damaged; increasing; acids; temperature; speed up; cytoplasm; break up; extreme; build; alkalis