Answer:

FACTORS AFFECTING THE RATE OF ENZYME ACTION:

 The functional specificity of every enzyme is the consequence of its specific chemical structure and arrangement. Any factor that can alter the chemistry and shape of an enzyme can affect its rate of catalysis. Some of the important factors that can affect,the rate of enzyme action are: 

1. Concentration of enzymes

2. Concentration of substrate 

3. Temperature 

4. pH of the medium.

 1. Enzyme Concentration:

 The rate of reaction depends directly on the amount of enzyme present at a specific time at unlimited substrate concentration. If the amount of enzyme is increased by two-fold, the reaction rate is doubled. By increasing the enzyme molecules an increase in the number of active sites takes place. More active sites will convert the substrate molecules into product(s), in the given period of time. After a certain limiting concentration, the rate of reaction will no longer depend upon this increase.

 2. Substrate Concentration:

 At low concentration of substrate the reaction rate is directly proportional to the substrate available. If the enzyme concentration is kept constant and the amount of substrate is increased, a point is reached when a further increase in the substrate does not increase the rate of the reaction any more  This is because at high substrate level all the active sites of the enzyme are occupied and further increase in the substrate does not increase the reaction rate.



3. Temperature:

 The rate of enzyme-controlled reaction may increase with increase in temperature but up to a certain limit. All enzymes can work at their maximum rate at a specific temperature called as optimum temperature. For enzymes of human body 37°C is the optimum temperature. Heat provides activation energy and therefore, chemical reactions are accelerated at high temperatures. Heat also supplies kinetic energy to the reacting molecules, causing them to move rapidly. Thus the reactants move more quickly and chances of their collision with each other are increased. However, further increase in heat energy also increases the vibrations of atoms which make up the enzyme molecule. If the vibrations become too violent, globular structure essential for enzyme activity is lost and the enzyme is said to be denatured. 

Example:

when albumin protein of egg is heated it change from liquid to somewhat solid and permanently changed.

  4. pH Value:

 pH stands for (power of hydrogen ion concentration) Every enzyme functions most effectively over a narrow range of pH known as the Optimum pH. A slight change in pH can change the ionization of the amino acids at the active site. Moreover, it may affect the ionization of the substrates. Under these change conditions enzyme activity is either retarded or blocked completely. Extreme changes in pH cause the bonds in the enzyme to break, resulting in the enzyme denaturation(nature of enzyme permanently change).

What are enzyme inhibitors? Also describe their different types?

Answer:

 INHIBITORS:

 An inhibitor is a chemical substance which can react (in place of substrate) with the enzyme but is not transformed into product(s) and thus blocks the active site temporarily or permanently, 

For example: poisons, like cyanide, antibodies, anti - metabolites and some drugs. 

Types of enzyme inhibitors:

 Inhibitors can be divided into two types:

1.  Irreversible inhibitors

2.  Reversible inhibitors .

1.  Irreversible Inhibitors: 

They check the reaction rate by occupying the active sites or destroying the globular structure. They occupy the active sites by forming covalent bonds or they may physically block the active sites. They may react with sulpha- hydryl (- SH) groups and precipitate the enzyme.

2. Reversible Inhibitors: 

They form weak linkages with the enzyme. Their effect can be neutralized completely or partly by an increase in the concentration of the substrate. Reversible inhibitors are further divided into two major types:

 1. Competitive inhibitors

 2. Non-competitive inhibitors

1.  Competitive Inhibitors:

Because of the structural similarity with the substrate they may be selected by the binding sites, but are not able to activate the catalytic sites. Thus product(s) are not formed.

2. Non Competitive Inhibitors:

They form enzyme inhibitor complex at a point other than the active site. They alter the structure of the enzyme in such a way that even if genuine substrate binds the active site, catalysis fails to take place.


Give the classification of enzymes according to their functions. 

Answer: 
CLASSIFICATION OF ENZYMES:

 According to the decision of International Union of Biochemists (IUB) in 1961. enzymes are divided into six groups.

1.  Hydrolases:

 These enzymes catalyze reactions in which substrates are  hydrolyzed into simple products. In this process hydrogen atoms from water molecule enter one of the products while hydroxyl groups end up in the other products. A general reaction for hydrolases is:

 AB + HOH ------------> AH + BOH

2. Oxidoreductases: 

The oxidation of substrate is catalyzed by this group of enzymes. They are of two kinds, oxidases and dehydrogenases. 

1. Oxidases: They catalyze the transfer of hydrogen atoms to a molecule of oxygen.

2AH2 + O2 --------------2A + 2H2O

2. Dehydrogenases: They catalyzed the oxidation of substrates by transferring hydrogen atoms to coenzymes such as NAD or NADP 

Ah2 + 2NAD --------------> A + 2NADH

 3. Transferases:

 They catalyzed the transfer of functional groups from one substrate to another.  

AB + C ------------->A + BC

4. Isomerases: 

They convert one form of isomer of a compound into the other isomeric form.  

ABC ------------------>ACB

5. Ligases:

 They catalyze reactions in which new chemical bonds are formed. They control the synthesis of macro-molecules such as proteins and ACB nucleic acids. ATP provides energy to form additional chemical bonds.

 6. Lyases: 

They catalyze the breakdown of complex substances into simpler products but water is not used as in hydrolytic reactions. 

AB  -------------> A + B


CHARACTERISTICS OF ENZYMES:

Enzymes have the following characteristics.

1. Enzymes are protein structures and are globular in shape.

2. They act like catalyst and speed up a certain biochemical process. 

3. They remain unchanged after the reaction is complete. 

4. They are specific in their function. 

5.Their action is affected by the amount of substrate, the rate of temperature etc.

6. They are sensitive to the changes in pH of the substrate. 

7. Like catalysts, enzymes reduce the activation energy necessary for a reaction. 8. A small amount of enzyme can bring about changes in a large amount of substrate. 

9. Some enzymes function properly only when a co-factor is attached to them. 

10. Each has an active site to which the substrate molecule is bounded.



Pre-medical ist year biology notes