Naturally occurring polymers- (nucleic acid)

Nucleic acid

These are biologically important polymers which are present in all living cells. They direct the synthesis of proteins and are responsible for transfer of genetic information i.e hereditary characteristics. The repeating unit in nucleic acids are called nucleotides. Thus the nucleic acid are basically polynucleotide. Each nucleotide is made up of three components.

1) A nitrogen containing heterocycle base which is of two types namely purines and pyrimidines.

a) The two purines are Adenine and Guanine.

Adenine.

Guanine.

b) The three pyrimidines are Cytosine, thymine and uracil.

Uracil.

Thymine.

Cytosine.

The two purines i.e Adenine and Guanine and pyrimidine Cytosine is present in both DNA and RNA. But uracil is present in RNA instead of thymine present in DNA.

2) A pentose sugar i.e either ribose or deoxyribose.

D-ribose.

D-deoxyribose.

3) A phosphate group

This group act as linkage between nucleic acid.

Phosphoric acid.

A pentose sugar at carbon 1' is linked to the nitrogen of the heterocycle base and this bond is called glycosidic bond and the compound formed is called nucleoside Fig(a). When the phosphate group is attached to ( carbon 5') of nucleoside a nucleotide is formed Fig(b) Next>>

Nucleoside.

Nucleotide.

Comments

Determination of molecular weight of polymers by viscosity method.

Determination of molecular weight of polymers by viscosity method. It is a simple method for determining the molecular weight of polymers. Addition of polymers in the solvent increases the viscosity of the solvent, due to introduction of inhomogeneities by the polymers. If η₀ is the viscosity of the solvent and η is the viscosity of the solution at the same temperature, then the relative viscosity is given by Relative viscosity. Specific viscosity: It is defined as the relative increase in viscosity and is given as Specific viscosity. Reduced viscosity: It is defined as the relative increase in viscosity per unit concentration (C) of polymer and is given as Reduced viscosity. Intrinsic viscosity: The reduced viscosity is dependent on concentration (C). If a graph is plotted between reduced viscosity vs concentration then the extraplotation value when C=0 is called intrinsic viscosity. Intrinsic viscosity. Graph of reduced viscosity vs concentr

Determination of molecular weight by Light scattering method.

Determination of molecular weight by Light scattering method. Due to big size macromolecules in solution, turbidity is produced. The light rays get scattered, when pass through macromolecule solution due to turbidity. The turbidity T is given by Where I₀ is the intensity of incident light. Iₜ is the intensity of transmitted light after passing through a solution of length l. In case of proteins or higher polymers the turbidity is small and is determine from the intensity of light scattered at 90° to the beam. This can be done by using a simple photometer as shown in figure below. Turbidity increase with increase in concentration as well as molecular weight. The Turbidity is related to molecular weight by the equation given by Debye. Hc/T=1/M+2Bc Where B is second virial coefficient and H is a constant. If we plot a graph between Hc/T vs c we get a straight line with intercept 1/M. Thus This curve was plotted by Zimm, so is called Zimm's Curve. Thus the c

Polypropylene (PP)

Polypropylene (PP). Polypropylene (PP) is also known as polypropene. Polypropylene is made from the polymerisation of propylene gas in the presence of Zeiglar Natta catalyst or metallocene catalyst. Polypropylene. Thus propene (or propylene) is the monomer of polypropylene. Polypropylene is a highly flammable material. It is sensitive to microbial attacks, such as bacteria and mold. It exhibits excellent resistance to diluted and concentrated acids, alcohols and bases. Polypropylene is used to make lunch boxes, margarine containers, yogurt pots, syrup bottles etc. Disposable syringes is the most common medical application of polypropylene. Polypropylene rope and twine are very strong and moisture resistant very suitable for marine applications. Polypropylene, highly colorfast, is widely used in manufacturing carpets, rugs and mats. Uses of Polypropylene. Questions on polypropylene; Q1) What is polypropylene? Ans) Polypropylene is a polymer of propylen

Polymers

Search This Blog