Change in amino acids sequence changes the protein completly. They have covalent bonds. It is the shape in which the long polypeptide chain can exist. It is of two types : α - helix and β - pleated. These structures arise due to regular folding of the backbone of the polypeptide chain due to H-bonding between the C=o and – NH- groups of the peptide bond. Represents overall folding of the polypeptide chain. It gives rise to the fibrous or globular molecular shapes. Forces stabilizing the 2 o and 3 o structures are hydrogen bonds, disulphide linkages, van der waal’s and electrostatic forces of Protein can be composed of two or more polypeptide chains called sub units. The spatial arrangement of these sub units with respect to each other is quaternary structure of the protein.
attraction. 12.Native State of Protein : The parental state or the natural state in which the protein is found. 13. Denaturaion of Protein: Destruction of the native state of protein is denaturation. It can be brought by physical and chemical methods. The 2 o and 3 o structures are destroyed, only 1 o structure is retained. Enzymes: These are biocatalyst and generally globular proteins e.g., invertase,zymase,phenyl, alaninehydroxylase, urease etc. Main Characteristics of Enzyme : 1.It speed up the biological reaction upto million times. 2.It is highly specific and work on lock and key theory. 3.It is highly sensitive to pH and temperature. 14. Vitamins: They are organic compounds required in the diet in small amounts to perform specific biological functions for maintenance of optimum growth and health of the organism. They are classified as follows (i) Fat Soluble Vitamins: Vitamin A,D,E and K. They are stored in liver and adipose tissues. (ii) Water Soluble Vitamins: B group vitamins and vitamin C. They need to supplied regularly in diet as they are excreted in urine and cannot be stored(except vitamin B 12 ) in our body. Their deficiency causes diseases.(Ref table in page no-418of NCERT book) Biotin (Vit H) is however neither fat nor water soluble. It’s deficiency leads to loss of hair. 15. Nucleic Acids: These are biomolecules which are long chain polymers of nucleotides. They are of two types: (i) Deoxyribonucleic acid (DNA) (ii) Ribonucleic acid (RNA) They are responsible for protein synthesis and transfer of genetic characteristics to offsprings. 16. Composition of Nucleic Acid: They are made up of pentose sugar(β -D-2-deoxyribose in DNA and β -D-ribose in RNA), phosphoric acid and a nitrogen containing heterocyclic compound(base). DNA- Bases present are Adenine(A), Thymine(T),Guanine(G) and Cytosine(C).
RNA- contains Adenine(A), Guanine(G), Cytosine(C) and Uracil(U). 19.DNA : has a double helical structure with AT and GC linked together through 2 and 3 hydrogen bonds respectively. It is responsible for transfer of genetic characteristics.
- Fall '09