1. The chemistry of life Organic Compounds: ENZYMES Heinemann – p166
Biozone – p51
Homework - Handout

2. Objectives for this lesson:
Contextualise Enzymes as Organic Compounds.
Distinguish the function of Enzymes in living organisms.
Compare the effect of various external factors on the functioning of Enzymes.
Apply theoretical knowledge to plan experiments related to enzyme function.

3. proteins Proteins are made up of the elements C, H, O & N.
They may also contain other elements such as S, P or Fe.
The building blocks or monomers of proteins are called amino acids.
Changes in the pH and temperature can change the structure of the protein. When this happens we say that the protein is denatured.
If a protein is denatured it cannot function.

4. Protein-functions: Proteins store energy.
They form cell components. This means that they make up parts of the cell like the cell membrane.
Enzymes and hormones are protein in nature.
All enzymes are proteins, but
not all proteins are enzymes.

5. ENZYMES Enzymes are organic catalysts.
A catalyst is a substance that speeds up a chemical reaction without being used up in the reaction.
This means they participate but
remain unchanged.
An organic catalyst is one that contains the element carbon and is usually protein in nature.

6. ENZYME Structure – 3d models

7. Enzyme-functions: Enzymes function as catalyst.
As catalysts they have 2 functions.
They speed up the chemical reactions without being used up during the chemical reaction.
They control and regulate all chemical reactions so that they occur at the best possible or optimum rate.

8. Optimum rate =
Optimum rate is the rate at which the most product is formed in the shortest space of time.

9. Enzyme-CHARACTERISTICS:
Enzymes are catalysts - start reactions of anabolic or catabolic nature.
Enzymes are specific in the functioning, thus one enzyme will react with a specific substrate only.
Enzymes are sensitive, specifically to changes in Temperature and pH.
Enzymes do not participate in chemical changes, they cause them, thus they remain unchanged.

10. SENSITIVITY: Lock and key theory
Most enzymes need the help of a partner.
This partner is organic and non- protein in nature. Usually vitamins.
The partner is called a co-enzyme / co-factor.
The co-enzyme is loosely bound to the enzyme and allows it to function with the specific substrate.

11. Lock and key theory / Mechanism
The substance on which the enzyme has an effect is called a substrate.
3. This is the part of the enzyme to which the substrate becomes
attached.
1. Each enzyme has a particular shape. This means it can inly react with certain substrate particles / molecules.

12. A C D B Lock and key theory
A- the substrate fits into the active site of the enzyme forming…
B- an enzyme-substrate complex
C- a chemical reaction occurs and the substrate changes shape
D- the enzyme and substrate separate and the enzyme can now react with more of the substrate A C D B

13. effect on temperature on enzyme activity
As the temperature increases, the rate of reaction also increase, until the temperature is about 37⁰C then enzyme activity is at it maximum.
This temperature is called the optimum temperature.
As the temperature increases further then enzyme activity starts to decrease because the temperature is too high and the enzymes become denatured.

14. Effect of pH on enzyme activity
The graph shows that the enzyme activity peaks at a certain pH.
This pH is called the optimum pH.
If the pH is lower or higher than this optimum pH, then enzyme activity decreases, because the enzyme becomes denatured.

15. Effect of ph on enzyme activity
This tell us that enzymes are very specific, that is a certain enzyme will only work in a certain pH.
For example: Salivary amylase only works in an alkaline medium (see digestive enzyme handout).

16. Effect of INHIBITORS on enzyme activity
Inhibitors - chemicals that reduce rate of enzymic reactions.
Specific and work at low concentrations.
Block enzyme but do not destroy it.
Many drugs and poisons are inhibitors

19. Lock & Key vs. induced fit

20. Use of enzymes in Industry
There are many uses of enzymes in industry:
They are used as meat tenderizers.
They remove hair from skins (leather production).
They are used in the making of beer, wine and vinegar.
They are also used to make chocolate and syrups.
They also used to make washing powders.

21. Use of enzymes in Industry (continued)
Most washing powders only contain one type of enzyme while some have more than one.
This is done to keep costs down.
Most washing powders contain protease.
Protease = enzyme that breaks down protein.
Therefore these washing powders can be used to remove stains caused by blood, egg and gravy.
Other washing powders contain amylase.
Amylase removes sugar based stains.

22. Answer this…
3. What is the enzyme activity at 20⁰ C? 4. At what temperature does enzyme activity start to decrease? Explain your answer. 5. What is the optimum temperature for this enzyme? 6. Use the graph to describe the relationship between enzyme activity and temperature.
Provide a suitable heading for the graph.
Name the dependent and independent variables.