## Note on Enzymes and Lipid

• Note
• Things to remember

### Enzymes.

Enzymes are the important group of globular proteins which acts as a biological catalyst that catalyses biochemical reactions in the living organism.

A typical cell contains about 3000 different kinds of enzymes. Unlike the chemical processes in the laboratory, most of the biochemical reactions in the living systems occur in aqueous solution with PH around 7.00 and at the physiological temperature of 37oC. These reactions are catalysed by enzymes. In the absence of enzymes, such biological process would take place extremely slowly. For instance, hydrolysis of amides or peptides in the laboratory require drastic condition like prolonging heating with an alkali solution, but hydrolysis of proteins (present in food) occurs quite rapidly in the presence of enzymes in the living systems.

One of the most remarkable characteristics of enzymes is specificity.It implies that the catalytic action of enzymes is highly specific. For example, maltose is an enzyme that catalyses the hydrolysis of maltose into two molecules of D- glucose. No other enzymes can substitute for maltose. Similarly, the enzymes carbonic anhydrous present in red cells of substitute for maltose. Similarly, the enzymes carbonic anhydrous present in red cells of blood catalyzes the reversible starch of carbonic acid to carbon dioxide and water.

$$H_2CO_3\xrightarrow{Carbonic\,anhydrase}H_2O+CO_2$$

The highly specific action of catalysts is attributed to its complex structure. The action of enzymes as a catalyst can be compared to lock and key. Just as a particular key can unlock the specific lock only not all the locks . Similarly, one type of enzymes cannot catalyse all the reactions.

The success of living forms is largely due to cell’s ability to make a large number of enzymes, each one specific to catalyse a particular reaction. No other type of catalyst can match the specificity and efficiency of enzymes. The deficiency of even one of the many enzymes in a body can cause serious disease. For example, some mentally retarded children suffer from a disease known as “phenyl ketone urea”, caused by the deficiency of the enzymes phenylalanine hydroxylase.

Function of enzyme

Enzymes play a vast number of specific function in human body among which some are given below.

1. Enzymes accelerate the rate of biochemical reactions (Metabolism ) in a human body.
2. Enzymes also promote the digestive reaction.
3. Enzymes catalyse fermentation process.
4. Enzymes converts starch into sugar.

#### Lipids.

Lipids are the most heterogeneous biomolecules that usually contain an alcohol and long chain organic acid I,e fatty acid. Fat, oil, wax, cholesterol and other related compound are included un lipid. They are generally water insoluble but freely soluble in the organic solvent like alcohol, ether, benzene etc. Lipid is found in wide variety of substance with different structure in plant animal and microorganism.

Classification of lipid.

Lipid is classified into three types. They are.

1. Simple lipid (oils and fat).
2. Phospholipid
3. Waxes

1. Simple lipid.

Simple lipid is also known as the homo lipid and is the ester of fatty acid with alcohol.

They are the most abduent group of lipid in plants and animals. These lipids are trimester of glycerol with long chain fatty acids. They have expressed as.

This tri ester is known as triglycerides. If the glyceride contains all the three same acid group, it is called simple glyceride and if the acid group are different, it is called mixed glyceride.Therefore, fat and oil are known as triglycerides or Triacylglyceride.

Fat.

The glyceride which contains the high level of saturated fatty acid components is called fat.They are solid at room temperature. Example butter,

Oil.

The glyceride which contains the high level of the unsaturated fatty acid component is called oil. They are liquid at room temperature. Example. Sunflower oil etc.

2. Phospholipid.

A phospholipid is mixed glycerides. In these, two OH groups of glycerol are esterified with higher fatty acid while the third OH group is esterified with some derivative of phosphoric acid. For example, Lecithin which is present in the egg.

3. Waxes.

Waxes are the ester of long chain fatty acid with high molecular weight mono hydroxy alcohol.

These are solid having melting point between 37-100oC. For example beeswax, Carnauba wax etc.

Soap and the process of saponification process.

Soap is sodium or potassium salts of some long chain fatty acids . Sodium salts of fatty acids are known as hard soap whereas potassium salts of fatty acids are known as soft soaps.

Saponification is the process of hydrolysis of fat in alkaline medium (i,e with NaOH or KOH) to give alcohol and sodium or potassium salts of carboxylic acids of higher fatty acids are known as saponification process. Example. The breakdown of fat to produce soap and glycerol is an example of saponification.

Reference

Bahl, B S, Bahl, and Arun. Advanced Organic chemistry. S. Chand and company Ltd., n.d.

Sthapit, M K, R R Pradhananga, and K B Bajracharya. Foundations of chemistry. Taleju Prakashan, n.d.

Tewari, K S, S N Mehrotra, and N K Vishnoi. A textbook of organic chemistry. Vikash publishing House Pvt. ltd., n.d.

Verma, N K and S K Khanna. Compressive chemistry. 8th edition. Laxmi publications P. Ltd., 1999.

1. Enzymes are the important group of globular proteins which acts as a biological catalyst that catalyses biochemical reactions in the living organism.
2. Lipids are the most heterogeneous biomolecules that usually contain an alcohol and long chain organic acid I,e fatty acid. Fat, oil, wax, cholesterol and other related compound are included un lipid.
3. The glyceride which contains the high level of saturated fatty acid components is called fat.They are solid at room temperature. Example butter.
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