1HSE Zoology Blog

• Biological catalyst.

• Almost all enzymes are protein.

• There are some nucleic acids that behave like enzymes. These are called ribozymes.

Carbonic anhydrase

Ribozymes

2HSE Zoology Blog

Inorganic catalysts

• Work efficiently at high temperatures and high pressures.

Enzyme catalysts

• Enzymes get damaged at high temperatures (above 40°C).

Vanadium Pentoxide

3HSE Zoology Blog

• Chemical compounds undergo two types of changes.

– Physical changes.

– Chemical changes(Chemical reaction).

4HSE Zoology Blog

• Change in shape without breaking of bonds.

Ice

Water

Water vapour

5HSE Zoology Blog

• Bonds are broken and new bonds are formed during transformation.

• Starch → Glucose

Ba(OH)2 + H2SO4 → BaSO4 + 2H2O

6HSE Zoology Blog

• Rate of a physical or chemical process refers to the amount of product formed per unit time.

7HSE Zoology Blog

• In the absence of any enzyme this reaction is very slow.

• I.e. 200 molecules of H2CO3/Hour.

8HSE Zoology Blog

• By using the enzyme carbonic anhydrase, the reaction speeds is 600,000 molecules /second.

• The enzyme has accelerated the reaction rate by about 10 million times.

9HSE Zoology Blog

• It is a metabolic activity in which glucose becomes pyruvic acid through ten different enzyme catalysed metabolic reactions.

10HSE Zoology Blog

• Enzymes bring down this energy barrier making the transition of substrate to product more easy.

11HSE Zoology Blog

EXOTHERMIC

12HSE Zoology Blog

E + S → ES → EP → E + P• The substrate binds to the active site of the enzyme, fitting into

the active site (E+S).

• The binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate (ES).

• The active site of the enzyme, now in close proximity of the substrate breaks the chemical bonds of the substrate and the new enzyme- product complex (EP)is formed.

• The enzyme releases the products of the reaction (E+P) and the free enzyme is ready to bind to another molecule of the substrate and run through the catalytic cycle once again.

13HSE Zoology Blog

14HSE Zoology Blog

15HSE Zoology Blog

• Each enzyme shows its highest activity at a particular temperature called the optimum temperature.

• Enzyme activity declines both below and above the optimum value.

• Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat.

Optimum temperature

16HSE Zoology Blog

• Each enzyme shows its highest activity at a particular pH called the optimum pH.

• Enzyme activity declines both below and above the optimum value.

Optimum pH

17HSE Zoology Blog

• With the increase in substrate concentration, the velocity of the enzymatic reaction rises at first.

• The reaction ultimately reaches a maximum velocity (V max) which is not exceeded by any further rise in concentration of the substrate.

• This is because the enzyme molecules are fewer than the substrate molecules .

• After saturation of these molecules, there are no free enzyme molecules to bind with the additional substrate molecules.

18HSE Zoology Blog

• The activity of an enzyme is also sensitive to the presence of specific chemicals that bind to the enzyme.

• Binding of the chemical shuts off enzyme activity –that chemical is called inhibitor and the process is called inhibition.

19HSE Zoology Blog

• When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor.

20HSE Zoology Blog

• Due to its close structural similarity with the substrate, the inhibitor competes with the substrate for the substrate binding site of the enzyme.

• Consequently, the substrate cannot bind and as a result, the enzyme action declines.

• Inhibition of succinic dehydrogenase by malonatewhich closely resembles the substrate succinate in structure.

• Succinate Succinic dehydrogenase

Malonate

21HSE Zoology Blog

22HSE Zoology Blog

• Enzymes are composed of one or several polypeptide chains(Proteins).

• The non protein part of the enzymes is called cofactor, which make the enzyme catalytically active.

• The protein portion of the enzymes is called the apoenzyme.

Protein Non protein Holoenzyme

Apoenzyme Cofactor Holoenzyme

23HSE Zoology Blog

Cofactor

Prosthetic group

Co enzymes Metal ions

24HSE Zoology Blog

• Organic compounds

• They are tightly bound to the apoenzyme.

• In peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group.

(Prosthetic group)

25HSE Zoology Blog

• Organic compounds • Their association with the

apoenzyme is only transient, usually occurring during the course of catalysis.

• The essential chemical component of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.

26HSE Zoology Blog

• A number of enzymes require metal ions for their activity.

• Zinc is a cofactor for the proteolytic enzyme carboxypeptidase.

27HSE Zoology Blog

Cofactor

Prosthetic group

Organic compounds.They are tightly bound to the apoenzyme.

In peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group.

Co enzymes

Organic compounds. Their association with the apoenzyme is only transient, usually occurring during the course of catalysis.

The essential chemical components of many coenzymes are vitamins coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.

Metal ions

A number of enzymes require metal ions for their activity

Zinc is a cofactor for the proteolytic enzyme carboxypeptidase.

28HSE Zoology Blog