1. WELCOME

2. 4.5 ENZYMES LEARNING OUTCOMES State what enzyme are
Explain why enzymes are needed in life processes
List the general characteristics of enzymes
Relate the name of enzyme to substrate
State sites where enzymes are synthesised
State the meaning of intracellular enzymes and extracellular enzymes
Explain the involvement of specific organelles in the production of extracellular enzymes

3. Explain the effects of pH,temperature,enzyme concentration and substrate concentration on enzyme activity
Explain the mechanism of enzyme action
Relate the mechanism of enzyme action with pH,temperature,enzyme concentration and substrate concentration
Explain the uses of enzymes in daily life and industry using examples

4. Example of enzyme

5. Role of enzymes in organisms
Enzymes are protein
Enzymes are biological catalyst that speed up the rate of biochemical reactions in the cells
Chemical reactions that occur within a living organism are called metabolism
Metabolic reaction starts with the substrate and ends with product

6. General characteristics of enzymes
Speed up the rates of chemical reaction but remains unchanged at the end of the reaction
Not destroyed by the reactions they catalyse
Highly specific that is each enzyme can only catalyse one kind of substrate
Needed in small quantities because they are not used up but released at the end of a reaction
Enzyme-catalyses reaction are reversible
Can be slowed down or completely stopped by inhibitors.
-e.g. : heavy metals such as lead and mercury
Require helper molecules called cofactors
Cofactors are divide by two:
organic cofactor like water soluble vitamin
Inorganic cofactor like ferum and copper

7. Naming of enzymes
An enzyme is named according to the name of the substrate it catalyses
Other enzyme were named before a systematic way of naming enzyme was formed
-e.g. : pepsin, trypsin and rennin

8. sucrase sucrose + water glucose + fructose
By adding suffix -ase at the end of the name of their substrate
Enzyme for catalysing the hydrolysis
Example :
sucrase
sucrose + water
glucose + fructose

9. substrate enzymes products
lactose
lactase
glucose + galactose
maltose
maltase
Glucose
cellulose
cellulase
lipid
lipase
Glycerol + fatty acid
starch
amylase
Maltose
protein
protease
Pepton + polypeptide

10. The sites of enzyme synthesis
Ribosomes are attached to the roughed endoplasmic reticulum.
Information for the synthesis of enzyme is carried by DNA
The different of bases in DNA are codes to make different protein
RNA is formed to translate the codes into a sequence of amino acids
Amino acids are bonded together to form specific enzyme according to the DNA’s codes

11. Intracellular and extracellular enzyme
Intracellular : synthesised and retained in the cell for the use of cell itself
: found in the cytoplasm, nucleus, mitochondria and chloroplast
Example : 1) oxydoreductase catalyse biological oxidation
2) reduction in the mitochondria
Extracellular : synthesised in the cell but secreted from the cell to work externally
Example : 1) digestive enzyme produced by the pancreas are not used by cells in the pancreas but are transported to the duodenum

12. Production of extracellular enzymes
Protein/Enzymes are synthesized in the ribosomes are transported through the spaces between the rough endoplasmic reticulum
Protein depart from the RER wrapped in vesicles that bud off from the sides of the RER
These transport vesicles fuse with the membrane of the Golgi apparatus
Secretory vesicles containing these modified protein bud off from the Golgi membrane and travel to the plasma membrane
These vesicles will then fuse with the plasma membrane before releasing the proteins outside the cells as enzymes.

13. The mechanism of enzyme action
The 'lock and key' hypothesis in of enzyme raection

14. Enzymes are complex protein made of one or more polypeptide chains
These polypeptide chain are folded into three-dimensional shape which include a pocket called an active site
The ‘lock and key’ hypothesis
The ‘substrate’ molecule represent the ‘key’
The ‘enzyme’ molecule represent the ‘lock’
The substrate molecule binds to the active site to form an enzyme- substrate complex
The enzyme catalyses the substrate to form products, then leave the active site
Enzyme molecule is now free to bind to more substrate molecules

15. Factor affecting enzyme activity
Temperature
At low temperatures, an enzyme-catalysed reaction takes place slowly
For every 10°C rise in temperature, the rate of reaction is doubled
However, this is only true up to the optimum temperature
Optimum temperature is the temperature at which an enzyme catalyses a reaction at the maximum rate
Effect of temperature

16. A normal enzyme molecule
Any increase in temperature will no longer increase the rate of reaction because the bonds that hold enzyme molecules together begin to break at high temperature, thus altering the three- dimensional shape eventually destroying active site
Enzymes lose their activities and are said to be denatured
So, organisms cannot survive at temperatures above 40°C
A normal enzyme molecule

17. Ph
The optimum pH is the pH at which the rate of reaction is at the maximum
A change in pH can alter the charges on the active sites of the enzyme and the substrate surfaces,it can reduce the ability of both molecules to bind each other
Pepsin can function in an acidic condition (pH 2) within in the stomach
Trypsin can function in alkaline condition (pH 8.5) within the duodenum

18. Substrate concentration
Increase in substrate concentration, more substrate molecule are available to bind the active sites of the enzyme
Hence, more products will be produced
Because more chances of collision between the substrate molecule and the enzyme molecules for a catalytic reaction to take place
In increase in substrate concentration will only speed up the reaction if there are enough enzyme molecules to catalyse the additional substrate molecules
The rate of reaction is directly proportional to the substrate concentration until the reaction reaches a maximum rate

19. After maximum rate, all active site of the enzyme molecules are filled and engaged in catalysis
The enzyme is said to be saturated
The concentration of enzyme becomes a limiting factor

20. Enzyme concentration
When the concentration of an enzyme increases,more enzyme molecules are available
The rate of of reaction will increase only if there is abundant supply of substrate molecules and other factors are constant because more active sites are made available for the catalytic reaction.
The rate of reaction is directly proportional to the concentration of the enzyme present until a maximum rate is achieved.
After the maximum rate,the doncentration of substrate becomes a limiting factor.
If the concentration of enzyme is doubled,the amount of substrate molecules also doubled.

21. The uses of enzymes
Can as catalysts in industries
The use of enzyme in industrial processes is known as enzyme technology.
Enzyme are use widely in our daily life
be use
enzymes
uses
protease
Tenderise meat
amylase
To convert starch to sugar in the making of syrup
lipase
Ripening the cheese
In detergent
Effectively dissolve protein stain