GENES The gene is a nucleic acid sequence that is necessary for function of gene product. Gene may be a protein coding gene whose transcribed RNA is translated into proteins or RNA only genes. Protein coding genes may be solitary or families or tandem repeats NON –CODING SEQUENCE The non coding sequence are genes that do not encode the protein. The amount of non-coding sequence in DNA of organism varies among species. Eg-Human genome -98% non-coding genes Prokaryotes -10% non-coding genes Types of Non coding sequences The non coding sequences can be in the form of following Introns Anti leader and Anti trailer sequence Promoter sequence Enhancers Pseudogenes Gene fragments Telomeres Non-coding functional RNA Cis-Trans regulatory elements INTRONS Introns are non-coding sequence that transcribed into RNA But precursor mRNA removed by splicing during processing. The eukaryotic genome has large amount of introns...
Polysaccharides are also known as polysoids or non sugars .It has high molecular weight substance.Polysaccharides are defined as hydrolysis of sugars into more than 10 sugar units.
Polysaccharides are classified into 2
1.Based on hydrolysis:
Based on hydrolysis polysaccharides are classified into two forms as
1.Homopolysaccharides
2.Heteropolysacharides
Based on metabolism classified as 2 forms
1.Nutrition or digestible
2.Structural or non digestible
Homopolysacharides
It is a process by which sugars are hydrolysed into same type of sugar units.
Heteropolysaccharides:
It is a process by which these sugar can hydrolysed into two different forms of sugar units.
Nutrition or digestible
It can be digested to absorb nutrition Eg:Starch
Structural or indigestible :
It cannot be digested but it has structural function.
1.Starch:
It is a polymer of glucose units
Occurrence:
It is found in tubers,roots,cereals etc...
Structure:
It is of two compounds as amylose and amylopectin
1.Amylose:
It is unbranched.It is with linear 1 to 4 linkage.Soluble in water.
2.Amylopectin:
It is branched with alpha 1 to 6 linkage.It is insoluble in water
Properties:
Physical property:
1.White 2.Amorphos 3.It form colloidal solution with water.4.It is soluble in organic solvents
Chemical properties
In iodine test forms blue violet solution.
Hydrolysis:
It hydrolysed in prescence of mineral acid to form glucose.
Enzymehydrolysis:
In presence of amylase enzyme it form maltose and lead to glucose units.
2.Glycogen:
It is a polymer of glucose units.
Structure:
It is formed by linkage of alpha -D glucose by alpha-1 to 6 linkage.
Properties
Physical property
1.White 2.Amorphous 3.insoluble in water 4.branched
Chemical properties
With iodine forms brown colour
Hydrolysis:
It hydrolyses to glucose in presence of mineral acids.
Cellulose:
It is structural unit of plants,lignin,legumes etc...
Structure:
It is a polymer of beta - D glucose by beta 1 to 4 like
It is unbranched.
Properties:
1.Rough 2.tough 3.amorphous 4.white 5.fibre
Enzyme hydrolysis:
In presence of cellulase enzyme it forms glucose units.
These cellulase units are found in cattle ruminants.
These cellulase enzymes are not found in human.
Inuline:
It is found in dandelion ,dahlias,onions and garlic.
It is polymer of fructose.
Structure:
It is a polymer of beta - D fructose linked together by beta 1 to 2 linkage.
Properties:
Physical property:
1.amorphous 2.powder 3.white 4.insoluble in water
Chemical properties:
It give brown color in iodine test.
Hydrolysis:
It is hydrolysed to form free fructose.
Dextrane:
It is a polymer of alpha D glucose linked by 1 to 4linkage but with branching of 1 to 2 ,1 to 3, 1 to 4 ,1 to 6 linkage.
Pectin :
It is found in guava, apples and pears
It is a polymer of alpha - D glucuronic acid.
It has 1 to 4 linkage.
It is having high solidity.Thus used in jams and jellies preparation .
Chitin:
It is found as biopolymer in insects and crustaceans.
It is of N- acetyl glucosamine linked together by alpha 1 to 4 linkage.
These are homopolysacharides,we can discuss heteropolysacharides in next post.
Comments
Post a Comment