General and physical characteristic of proteins

(i) Most of them (except chromoproteins) are colourless, tasteless, and odourless. Many are amorphous but few are crystalline. They are nonvolatile and do not have a sharp melting point .

(ii) Most of them are insoluble in water and alcohol. But many of them dissolve in salt solutions, dilute acids and alkalies. Some proteins such as keratins (skin, hair and nails) are completely insoluble.

(iii) Protein molecules are very complex and possess very high molecular masses. They are hydrophilic colloids which cannot pass through vegetable or animal membrane. On addition of sodium chloride, ammonium sulphate magnesium sulphate, etc., some proteins are precipitated. The precipitate can be filtered and redissolved in water.

(iv) The solution of proteins are optically active. Most of them are laevorotatory. The optical activity is due to the presence of asymmetric carbon atoms in the constituent a-amino acids.

(v) Isoelectric point : Every protein has a characteristic isoelectric point at which its ionisation is minimum. Like amino acids, proteins, having charged groups (NH₃⁺ and COO^-) at the ends of the peptide chain, are amphoteric in nature. In strong acid solution, protein molecule accepts a proton while in strong basic solution it loses a proton. The pH at which the protein molecule has no net charge is called its isoelectric point. This property can be used to separate proteins from mixture by electrophoresis.

(vi) Denaturation : The structure of the natural proteins is responsible for their biological activity. These structures are organized by various attractive forces between different parts of the polypeptide chains. The breaking of these forces by a physical or a chemical change makes the proteins to lose all or part of their biological activity. This is named denaturation of proteins. The denaturing of proteins can be done by adding chemicals such as bases, acids, organic solvents, heavy metal ions, or urea. It can also be done with the help of heat and ultraviolet light. Denaturation may be reversible or irreversible. In irreversible denaturation, the denaturated protein does not return to its original shape. For example, the heating of white of an egg (water soluble) gives a hard and rubbery insoluble mass.

Email based Chemistry assignment help - homework help at Expertsmind

Are you searching chemistry expert for help with General and physical characteristic of proteins questions?  General and physical characteristic of proteins topic is not easier to learn without external help?  We at www.expertsmind.com offer finest service of Chemistry assignment help and chemistry homework help. Live tutors are available for 24x7 hours helping students in their General and physical characteristic of proteins related problems. We provide step by step General and physical characteristic of proteins question's answers with 100% plagiarism free content. We prepare quality content and notes for General and physical characteristic of proteins topic under chemistry theory and study material. These are avail for subscribed users and they can get advantages anytime.

Why Expertsmind for assignment help

1. Higher degree holder and experienced experts network
2. Punctuality and responsibility of work
3. Quality solution with 100% plagiarism free answers
4. Time on Delivery
5. Privacy of information and details
6. Excellence in solving chemistry queries in excels and word format.
7. Best tutoring assistance 24x7 hours