Proteins

Proteins are organic complex nitrogenous compounds of high molecular weight, formed of C, H, O and N. They are formed of a number of amino acids linked together by peptide linkage [-CO-NH-].

Proteins are essentially natural polymers composed of long chains of subunits. These smaller units are called amino acids. One "end" of an amino acid has acidic character because it has a carboxyl (COOH) functional group. The other end has basic character because it has an amino (NH 2) functional group. When two amino acids react, they form what is called a peptide bond. The resulting molecule, called a dipeptide, still has one end that is acidic and another that is basic. With this fundamental reactive pattern, it is possible to string together many amino acids to form a polypeptide. For such a chain, the end that has the carboxyl group is referred to as the C-terminus; the amino end is referred to as the N-terminus. Proteins are made from many amino acids. They are connected together by peptide bond. Peptide bonds are formed by condensation, the loss of a water molecule and between the carboxyl group with the amino group.

Example;

Different levels of protein structure

The four levels of protein structure are: primary structure, secondary structure, tertiary structure, and quaternary structure.

Primary structure simply refers to the linear sequence of amino acids joined to each other through peptide bonds. The sequence of amino acids determines the basic structure of the protein.

These folded structures are referred to as secondary protein structures and are essentially of two types—alpha helix and beta pleated sheets. These folded secondary structures are stabilized by the formation of hydrogen bonds between the amino acids.

Tertiary structure: When several secondary structures come together, tertiary structures are formed.

Quaternary structure: When several tertiary structures come together, a quaternary protein structure is formed. For example, hemoglobin is a functional quaternary protein formed by the coming together of four tertiary structures, called globin proteins.

Examples of proteins: Keratin, actin, myosin, haemoglobin, collagen, elastin, albumin, fibrin and insulin.

Proteins perform essential functions throughout the systems of the human body. These long

chains of amino acids are critically important for:

catalyzing chemical reactions

synthesizing and repairing DNA

transporting materials across the cell

receiving and sending chemical signals

responding to stimuli

providing structural support

Fats and Oils

Fats and oils are the most abundant lipids in nature. They provide energy for living

organisms, insulate body organs, and transport fat-soluble vitamins through the blood.

Fats and oils are called triglycerides (or triacylcylgerols) because they are esters composed of

three fatty acid units joined to glycerol, a trihydroxy alcohol:

If all three OH groups on the glycerol molecule are esterified with the same fatty acid, the

resulting ester is called a simple triglyceride. Although simple triglycerides have been

synthesized in the laboratory, they rarely occur in nature. Instead, a typical triglyceride

obtained from naturally occurring fats and oils contains two or three different fatty acid

components and is thus termed a mixed triglyceride.

A triglyceride is called a fat if it is a solid at 25°C; it is called oil if it is a liquid at that

temperature. These differences in melting points reflect differences in the degree of

unsaturation and number of carbon atoms in the constituent fatty acids. Triglycerides

obtained from animal sources are usually solids, while those of plant origin are generally oils.

Therefore, we commonly speak of animal fats and vegetable oils.

There are three main types of fatty acids: saturated, monounsaturated and polyunsaturated.

All fatty acids are chains of carbon atoms with hydrogen atoms attached to the carbon atoms.

Saturated fatty acids: Fatty acids contain carbon-carbon single bonds called saturated fatty

acids.

Examples: stearic acid (C17H35COOH) & palmitic acid (C15H31COOH)

Unsaturated fatty acids: Unsaturated fatty acids contain one or more double bonds between

carbon atoms. Example: Oleic acid (C17H33COOH)

If the fatty acid has a single carbon-carbon double bond in the molecule, it is known as a

mono-unsaturated fatty acid. Oleic acid is a mono-unsaturated fatty acid.

If a fatty acid has two or more carbon-carbon double bonds in the molecule, it is known

as poly-unsaturated fatty acid.

Linoleic acid { CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH } is a poly-unsaturated fatty

acid. It contains two double bonds.

Long chain fatty acids always exist as triglycerides and are found in fats and oils.

Triglycerides are esters of fatty acids and are formed by combining fatty acids with glycerol.

The fat in foods contains a mixture of saturated, monounsaturated and polyunsaturated fatty

acids. In foods of animal origin, a large proportion of fatty acids are saturated. In contrast, in

foods of plant origin and some seafood, a large proportion of the fatty acids are

monounsaturated and polyunsaturated.

Saponification: It is a process by which triglycerides are reacted with sodium or potassium

hydroxide to produce glycerol and a fatty acid salt, called 'soap'. When sodium hydroxide is

used, a hard soap is produced. Using potassium hydroxide results in a soft soap. Since this

reaction leads to the formation of soap, it is called the Saponification process.

Organic Solvents

Organic solvents are used by everyone in most of the daily activities starting right from the

disinfectant treatment to the removal of tough grease stains. The perfumes or cologne we use,

laundry detergents which are used to keep clothes fresh and clean, all these products contain

those ingredients called as Organic solvents.

Organic solvents are those chemicals compounds having carbon-based molecular structure.

These are widely used in dissolving material in-order to create a solution, or even in

extraction of one material from another material. In general, a solvent refers to the substance

which is capable of dissolving any other substance. An organic solvent is a type of volatile

organic compound (VOC). VOCs are organic chemicals which vaporise at room temperature.

E.g. Acetone, ethanol, benzene, ethyl acetate, chloroform, isopropanol etc

The molecular structure of an organic solvent always contains a carbon atom and some have

hydrogen atoms. These solvents are mainly categorized based upon their molecular structures

as natural and synthetic solvents.

Natural solvents– These are the solvents which are naturally produced by living organisms.

Synthetic Solvents– These are the solvents which are produced as a result of chemical

reactions occurring in various organic compounds.

Types of Organic Solvents

Based upon the structure and the functional group, the different types of organic solvents are

as explained below-

Aliphatic solvents– These solvents belong to the class of alkenes. They are said to be

non polar in nature. Some of the applications of such solvents include oil extraction,

paint, dye, pharmaceuticals, in polymerization and adhesives.

Aromatic solvents– These like the aliphatic are said to be non polar solvents. They

are utilized as industrial solvents for adhesives, paints, printing inks, extraction

processes, decreasing, in insecticides, etc.

Carbonyls solvents– These includes esters. They are said to exhibit polar properties

and are used in the nail paint removers, electronic cleaners, circuit boards,

decaffeination, in glues, and also in food flavouring substances.

Some of the other solvents include alcohols which are used in various industrial and

commercial applications.

Properties of Organic Solvents

Organic solvents do exhibit various physical and chemical properties as given below-

Organic solvents are volatile in nature– Volatile solvents are those which have the

ability to vaporise. Organic solvents possess these properties. Due to nature of

volatility, organic solvents release smell when released into air.

Organic solvents exhibit low boiling point- Organic solvents are said to have very

low boiling points. Due to this low boiling point, they are highly volatile.

Organic solvents are colourless liquids- These are clear liquids and have lower

molecular weights.

Applications of Organic Solvents

Organic solvents find its uses in different areas. These are used in coatings, polishes, as an

paint thinner and remover( toluene), as cleaning agents, as a nail polish remover( acetone,

ethyl acetate, methyl acetate), as an industrial as well as consumer degreasers, detergents,

perfumes, spot removers and also in various chemical syntheses and processes.

Organic solvents react in the atmosphere in sunlight, producing an air pollutant known as

'ground-level ozone'. High concentrations of ground-level ozone seriously affect human,

animal and plant health. They also harm building materials, forests and crops.

Many organic solvents are classified as toxic or carcinogenic. They can cause significant air

and water pollution, and land contamination.