1. The cell’s essential molecules
Enzymes
The cell’s essential molecules

2. The Importance of Enzymes
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 !

3. Enzyme 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.

4. An enzyme in
the cell’s
cytoplasm
splitting
a dangerous
substance into
two harmless
ones.

5. An Enzyme at Work

6. Enzymes and Temperature
Enzymes 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!

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

8. Enymes and Temperature continued
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.

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

10. Enzymes in Danger • Enzymes are very complex protein molecules.
• When they come in contact with very high
temperatures they start to change shape.
• If their shape is changed they can no longer work
as enzymes !
• Acids and alkalis also damage these complex
molecules !

11. Effects of Temperature and Acids and Alkalis
After heat or contact with acid
the protein unravels and no
longer functions as an enzyme!
The enzyme is denatured.
Enzyme before treatment - a
complex protein.

12. More about Temperature and enzymes
The 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 B
2. To the activity at point B
3. To the activity between points B and C
4. To the enzyme between points B and C
5. Think carefully - why was no measurement made at 0°C ?

13. This graph shows what happens to they way an enzyme reacts over a range of temperatures !

14. Enzyme fact file
Copy 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