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Kay shall upload enzyme now! Enjoy. Please refer to ur notes for diagrams and pic cuz i dun hav a scanner. If u have question u can ask me on msn, Other chapter shall come soon

Science Note (BIOLOGY) MYE 2009 edition
By: Samuel Chiang Li Hsin (26) 2J

Enzymes
What is enzyme?
Biological catalyst that are made out of protein. They alter the rate of chemical reaction without themselves being chemically changed at the end of reaction.

Example of enzyme-catalysed reactions
1. Digestion of food (amylase, protease and lipase etc)
2. 2.Build up of complex substances (From amino acids to protein)
3. Breakdown of complex substances.(Breakdown of toxic hydroxide)

Characteristics of enzyme
Highly specific (lock and key hypothesis)
Temperature sensitive
pH sensitive
Speed up chemical reaction
Required in minute amount and remain unchanged

How do enzymes bring about an increase in the rate of reaction?
They lower the activation energy needed for a reaction to occur.

Reaction Energy (EA)The minimum amount of energy required to initiate a reaction.

Why are enzymes so specific in their action?
Enzymes are specific due to their 3D shape and surface configuration
Surface configuration of substances must be complementary to the active site of the enzyme.

The Lock and Key Hypothesis (refer to note given by teacher)

What is the effect of temperature on enzyme activity?
-As the temperature increases toward the optimum temperature, the amount of kinetic energy in the enzyme and the substrate increases, increasing effective collision between the enzyme and the substrate forming enzyme substrate complex.
-At the highest point of the curve, the temperature hit the optimum temperature of the enzyme, resulting in maximum enzyme reaction.
-At temperature beyond the optimum temperature the enzyme denatures and the rate of reaction decrease drastically.

Different enzyme has different optimum temperature where the activity of the enzyme is maximum.

Most enzymes in the human body has maximum temperature around the human temperature

At low temperatures, enzymes are inactive resulting in low rate of reactions.

What is the effect of pH on enzyme activity?
Enzymes are affected by acidity and alkalinity of solutions.
The optimum pH is the pH which enzymes has the highest activity
Extremes of pH will denature and inactivate enzymes.
Different enzyme has different pH

What are the effects of substrate and enzyme concentrations on rate of reaction?
Substrate concentration
Increasing substrate concentration will cause the rate of reaction to increase till a point where all active site of the enzymes are all occupied, causing no significant change in reaction rate.

Enzyme concentration
Enzyme concentration will result in higher rate of concentration as there are more active sites for substrates. However the rates of reaction will remain constant once all active site of enzymes are occupied

Denaturation
Enzymes are made out of chains of amino acids held together via hydrogen bonds.
At high temperature, these hydrogen bonds are broken
Structure loses it shape and therefore its active site
Enzyme is denatured

What is a limiting factor?
Definition: A limiting factor is any factor which by its availability, would determine how fast a reaction would take place.
Eg: Temperature, pH changes, Substrate &enzyme concentration

Industrial applications of enzyme:
a) Meat tenderiser
The enzyme found in meat is papain (found in papaya and other plants)
Papain cuts the protein chains in the tissues of meat, disrupting the structural integrity of muscle fibre; and tenderising the meat.

b) Biological washing powders
Enzymes: Protease, amylase, lipase
A range of different enzymes are used in biological washing powders to remove stains which are made out of different types of molecules.

c) Diagnostic Kits
Application of enzyme to detest certain chemical molecules
Eg. Cholesterol, progesterone, testosterone
-Advantages: low sample volume, high specificity and high stability

Food Test
Reducing Sugar (carbohydrates such as glucose, fructose and maltose) - Benedict’s test
1. Add 2cm3 of Benedict’s solution.
2. Shake well
3. Heat in boiling water bath for no more than 5 minutes
If orange precipitate formed, reducing sugar present
Protein- Biuret Test
1. Add 2cm3 of sodium hydroxide
2. Shake Well
3. Add 1%copper (II) Sulphate solution drop wise. Shake after each drop
If solution turned violet mean proteins present
Starch-Iodine Test
1. Add a few drop of iodine
If iodine solution turn blue black starch is present.
Fats/Oils- Ethanol-emulsion test
1. Add 2cm3 of ethanol
2. Shake Well
3. Add 2cm3 of water
If white emulsion formed means Fat/Oils is present
Assignment Section B
1a) Name two properties illustrated by the figure (please refer to the assignment)
1. Enzyme is substrate specific
2. Enzyme remain chemically unchanged after the reaction
b) Name two properties not illustrated by the figure
1. Enzymes are specific due to their 3D shape
2. Enzyme lower the activation energy needed for a reaction to occur.

2a) by referring to figure, explain why only small amount of energy is needed to catalyse a reaction involving many molecules? (Refer to assignment)
The enzymes alter the rate of chemical reaction without themselves being chemically changed at the end of reaction and can be used again

b) Explain how a rise in temperature may increase the rate of an enzyme controlled reaction.
As you increase the temperature, the kinetic energy of the enzyme and substrates increases, resulting an increase in effective collision of enzyme and substrate, forming the enzyme substrate complex. Hence, increasing the rate of reaction.

d) At high temperatures, enzymes are denatured and can no longer act as catalysts. Suggest what happens when enzyme is denatured.
At high temperature, active site is destroyed and the substrate can no longer fit in to form the enzyme substrate complex and then the product.

3a) Explain why curve P represent the amount of substrate (Refer to assignment again)
Enzyme catalyses the break down of substrate. As product concentration increase the substrate concentration should decrease according.

b) Explain the shape of curve u added
During germination, starch is used up. When seedling develops leaves, it is able to photosynthesise. During photosynthesis, glucose is formed and excess glucose will be converted to starch to be stored.
Section D
Critique on what he mentioned about enzyme, base on your knowledge what extend do you agree?
Enzymes are biological catalyst not all enzymes are made out of protein, There is an enzyme made out of RNA. Different enzymes will have different optimum temperature. Enzymes are inactivated at low temperature, not denatured. There are enzymes found in other places as well. And enzymes also have other uses.

Why are Enzymes specific?
Enzyme specificity is due to the 3-dimensional shape (surface configuration). Surface configuration of substrates must be complementary to the active site of the enzyme in order for activity to take place.
According to lock and key hypothesis, the substrate binds to the enzyme, forming enzyme-substrate complex. In this hypothesis, the enzyme is the lock while the substrate is the key.

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