Biology [Chapter # 06]

 

CHAPTER# 06

ENZYMES

 

Q. Define Anabolism, catabolism and Activation energy.

ANABOLISM

In constructive reactions large molecules are formed to form a structure of cell or body. These reactions are called anabolic reactions and this type of metabolism is called anabolism.

CATABOLISM

The destructive reaction in which large molecules breakdown in small molecules to produce energy or to re-utilize further or to discard called catabolic reactions. The type of this metabolic activity is called catabolism.

ACTIVATION ENERGY

 

Each reaction requires some amount of minimum energy to initiate a reaction. This minimum amount of energy is called activation energy.

 

 

Q. Define Enzymes. Describe the characteristics of enzymes.

ENZYMES

Enzymes are the biocatalyst which can speed up or speed down the chemical reaction. They are mostly made up of proteins.

 

CHARACTERISTICS OF ENZYMES

·        Enzymes are biocatalyst, made up of mostly proteins and therefore three dimensionally folded chains of amino acids with a specific shape.

·        Enzymes speed up reactions by bringing reactants together and reducing the activation energy required to start the reaction (enzymatic reaction)

·        A single or little amount of enzyme can start a reaction and catalyze fast.

·        Their presence does not affect the nature or properties of end products.

·        Reactants of enzyme are called substrate.

·        They are very specific in their action; a single enzyme catalyzes only a single chemical reaction or a group of related reactions.

·        A small portion of enzyme where substrate attaches with enzyme is called active site. The shape of active site is complementary to shape of the substrate

·        They are sensitive to even a minor change in pH, temperature and substrate concentration.

·        Some enzymes require cofactor for their functioning; a cofactor is a non-protien substance which may be organic or inorganic. Zn⁺² , Mg⁺², Mn⁺² , Fe⁺² , Cu⁺² , K⁺¹ and Na⁺¹ the organic cofactors are NADP, NAD and FAD are used in enzymes as cofactors.

·        Many enzymes work in a sequential manner to produce a specific product. This pathway is called metabolic pathway.

·        An enzyme inhibitor is a molecule that binds to an enzyme and decreases its activity.

·        Enzymes are specific in their nature for instance protease are the enzymes which catalyze the proteins and lipase acts on lipids only.  

 

Q. Give the uses of Enzymes.

USES OF ENZYMES

Many enzymes are used commercially in industries. The most common industries are:

·        Paper industry- To get cellulose for paper making.

·        Food industry- For making bakery products and pizza.

·        Brewing industry- For conversion of sugar into alcohol.

·        Bio-detergents- Use to remove different type of stains.

 

Q. Describe the factors affecting on Enzyme activity.

FACTORS AFFECTING ON ENZYME ACTIVITY

SUBSTRATE CONCENTRATION

•      Increase with increase in substrate concentration (up to a limit)

•      At very high concentration, activity again decreases due to saturation of enzyme with substrate and saturation product.

TEMPERATURE

•      Increases with increase in temperature (up to a limit)

•      Maximum activity at optimum temperature

•      Highly active at 37⁰  C and destroyed at 100⁰ C

•      At 0⁰ C minimum activity

pH

•      Enzymes are pH specific i.e. work in specific pH

•      (because of protein can act both in acidic and

•      basic medium)

WATER

•      Enzyme activity is usually maximum (up to

•      limits) but decrease after limits (dilution of

•      enzymes)

RADIATIONS

•      Enzymes become inactive due to radiations

•      (including alpha, beta, gamma rays)

Q. Describe the mechanism of Enzyme action.

MECHANISM OF ENZYME ACTION

Enzyme catalyzes the reaction by attaching to substrate which ends to the product formation. Enzyme exposes its active site to attract specific substrate, makes enzyme substrate complex (ESC) after which the product is formed and enzyme is detached from it and used again for the same reaction.

Q. How can you describe Action of enzyme?

ACTION OF ENZYME

In order to understand the mechanism of enzyme action two theories are proposed; Lock and key model and Induced fit model.

KEY AND LOCK MODEL (FISCHER 1898)

This theory was first postulated by Emil Fischer in1894 shows the high specificity of enzymes.

•      Modified by Paul Filder and D.D Woods

•      Active site of enzyme has distinct shape

•      It allows few substrate to fit in (like a particular lock allows particular key to fit in)

•      Enzyme break substrate to product

INDUCE FIT MODEL (KOSHLAND 1959)

•      Enzyme binds with  a substrate

•      The binding induce changes in enzyme structure

•      Due to change, enzyme act and form product.