Question

What are the four classes of biological macromolecules? For each of the four classes, tell a) what they are made of (what's the monomer or building block) and b) what they're used for in the body and in what way are all four groups similar in chemical composition, i.e., why are they called organic molecules?

Answer 1

The four classes of biological macromolecules are as:-

1) Carbohydrates.

2) proteins.

3) Lipids.

4) Nucleic acids.

a) carbohydrates:-

1) Carbohydrates are polyhydroxy aldehydes or ketones and their condensation products.

2) Aldehyde group is generally terminal while ketone group is commonly subterminal.

3) Both them are active groups of carbohydrates.

4) Depending upon the presence of aldehyde or ketone group, Carbohydrates are called aldoses and ketoses.

5) The empirical formula is C_{​​​​​n^(H2O⁾n or} (CH₂O)n where the value of integer n is 3-7 for monomers.

Proteins:-

1)Proteins are large sized mixed polymers or heteropolymerers of several types of Alpha - amino acids joined by peptide linkaes into linear chains that get folded variously.

2)Proteins form the colloidal complex of the protoplasm, form cell membranes and many biomolecules.

3) Proteins are also a major component of animal diet.

4) The proteins which are able to supply all the amino acids including the essential and semi- indispensable ones are called complete proteins or first class proteins.

5) Proteins are the most abundant organic molecules of the cell, forming up to 50% of its dry mass.

Lipids:-

1) Lipids are a heterogeneous group of fats and fat like substances which are insoluble in water but soluble in non polar solvents like ether, acetone chloroform and carbon tetrachloride e.g, ghee, butter.

2) Insolubility in water is due to presence of long complex nonpolar hydrophobic hydrocarbon chains.

3) If shaken with water lipids often form small droplets or micelles.

4) It is a modified colloidal complex called emulsion.

5) Lipids are formed of carbon, hydrogen and often oxygen .where oxygen content is very small as compared to other two elements.

Nucleic acids:-

1) Nucleic acids are linear mixed polymers of purine and pyrimidine nucleotides.

2) they are also called polynucleotides.

3) Nucleic acids are macromolecules which seperate out in acid insoluble pellet.

4) Nucleic acids were first isolated by Swiss physician Friedrich Miescher from nuclei of pus cells and named nuclei.

b) Function :-

Proteins

Structural and supporting proteins they form extracellular structures like matrix of connective tissue, tendond and bones.

Protective proteins. Keratin is the main component of external protective structures like dead layers of skin, hair etc.

Nucleic acids

It occurs in nucleus mitochondria and plastids.

One found in mitochondria and plastids are called organelle DNA.

Lipids

It helps in formation of bile salts and bile acids

It forms vitamin D near the surface of irradiated skin.