In both the amino acids the common substituent groups are $\mathrm{NH}_2 \mathrm{COOH}$ and H .
Starch, cellulose, glycogen, chitin are polysaccharides found among the following. Choose the one appropriate and write against each.
Cotton fibre ...............
Exoskeleton of cockroach ..............
Liver ...............
Peeled potato ..............
(a) Cotton fibre-Cellulose
(b) Exoskeleton of cockroach - Chitin
(c) Liver-Glycogen
(d) Peeled potato - Starch
Cellulose is a long chain of linked glucose molecules and is the main component of plant cell walls. Cotton is the purest natural form of cellulose. the cellulose content of cotton fibre is $90 \%$.
Chitin is a long chain polymer that forms the hard part of the outer integument or exoskeleton of crustaceans and insects such as cockroach. It is also the main component of the cell walls of fungi.
Glycogen is a multibranched polysaccharide of glucose acting as a form of stored energy in the liver of animals. It is also found in some stored fungi.
Starch is a carbohydrate consisting of along chain of glucose units joined by glycosidic bonds. This polysaccharide is produced mostly by green plants for energy storage, e.g., peeled potato.
Enzymes are proteins. Proteins are long chains of amino acids linked to each other by peptide bonds. Amino acids have many functional groups in their structure.
These functional groups are many of them at least, ionisable. As they are weak acids and bases in chemical nature, this ionisation is influenced by pH of the solution. For many enzymes, activity is influenced by surrounding pH . This is depicted in the curve below, explain briefly.
Enzymes, generally function in a narrow range of pH . Most of the enzyme shows their highest activity at a particular pH called optimum pH , and it declines below and above this value.
Extremely high or low pH values generally results in complete loss of activity for most enzyms. The graph above represents the maximum enzyme activity at the optimum pH .
Rubber (cis 1, 4-polyisopyrene) is a secondary metabolite. Secondary metabolites are chemicals produced by plants for which no role has been found yet in growth, photosynthess, reproduction or other primary functions.
(i) Rubber is extracted from Havea brasiliensis (rubber tree).
(ii) It is a byproduct of the lactiferous tissue of the vessels that are in the form of latex.
(iii) It is the largest of the terpenoids because it contains over 400 isoprene units.
(iv) It is elastic, water proof and a good electrical conductor.
Proteins are the large-sized, heteropolymeric macromolecules having one or more polypeptides (chains of amino acid). Primary Structure The primary structure of a protein is the linear sequence of amino acid structural units and partially comprises its overall biomolecular structures. The amino acids are linked together in a sequence by peptide bonds.
In the primary structure of protein initiate from an amino-terminal $(\mathrm{N})$ to the carboxyl terminal (C) end,
Secondary Structure It is a three dimensional form of local segments of bipolymers such as proteins. Secondary structure of proteins is defined by hydrogen bonds between backbone amino and carboxyl groups. Mainly secondary structure in proteins possess two forms, i.e., $\alpha$-helix and $\beta$-pleated sheet.
$\alpha$-helix is a polypeptide chain spirally coiled to form a right handed helix. This helix may be coiled regularly at places and at some places randomly coiled. The helix is stabilised by many hydrogen bonds which are formed between - CO of one amino acid and - NH group of next fourth amino acid.
$\beta$-pleated sheets two or more polypeptide chains are joined together by intermolecular hydrogen bonds to produce a sheet like structure instead of fibre as in $\alpha$-helix. The polypeptide strands in a sheet may run parallel in same direction, e.g., keratin or in opposite direction called antiparallel $\beta$-sheet, e.g., fibroin.
Tertiary structure involves interactions that are caused by the bending and folding of $\alpha$-helix or $\beta$-sheets leading to the formation of rods, spheres of fibres. Such interactions are typically conferred by H-bonds, ionic bonds, covalent bonds, van der Waat's interactions and hydrophobic interactions or disulphide linkages. It gives the protein a three dimensional conformation.
