Amino Acid coo Peptide Bond PROTEINS Proteins are polypeptides. They are linear chains of amino acids linked by peptide bonds
The acid insoluble pellet also has polysaccharides (carbohydrates) as another class of macromolecules. Polysaccharides are long chains of sugars. They are threads (literally a cotton thread) containing different monosaccharides as building blocks. For example, cellulose is a polymeric polysaccharide consisting of only one type of monosaccharide i.e., glucose. Cellulose is a homopolymer . Starch is a variant of this but present as a store house of energy in plant tissues. Animals have another variant called glycogen. . Inulin is a polymer of fructose.
* In a polysaccharide chain (say glycogen), the right end is called the reducing end and the left end is called the non-reducing end. It has branches as shown in the form of a cartoon .Starch forms helical secondary structures. In fact, starch can hold 12 molecules in the helical portion. The starch- 12 is blue in colour. Cellulose does not contain complex helices and hence cannot hold 12
CH2OH CH OH 6 CH20H CH2OH o 1 CH2OH OH OH CH2OH H CH2OH OH Glucose Fructose Galactose Glucose Fructose (a) Hexoses CH2OH CH2OH OH HOCH2 OH CH2OH Deoxyribose Ribose crose Glycosidic Bond (b) Pentoses
. Plant cell walls are made of cellulose. Paper made from plant pulp and cotton fibre is cellulosic. There are more complex polysaccharides in nature They have as building blocks, amino-sugars and chemically modified sugars (e.g., glucosamine, N-acetyl galactosamine, etc) . Exoskeletons of arthropods, for example, have a complex polysaccharide called chitin. . These complex polysaccharides are mostly homopolymers.
H C OH CH OH HOCH OH OH H OH OH H HO H O OH (a) and glucose ring structures CIHOH CI2OI CI2O 0 HO OH OH Q H glucose OH (b) Starch:4 kage of CH OH OI I OI HO OH OH CH2OH CH OH (c) Cellulose 14 linkage of B glucose
CH OH CH20H CH2OH OH OH a-1,6 linkage Nonreducing ends CH2OH a-1,4 linkage CH20H 4 OH HO OH OH
CH OH CH2OH OH OH OH OH
Nonreducing end (no potential for free at anomeric position) C-O Reducing end (ring can open to yield free C-O at anomeric carbon) CH20H CH3OH OH OH
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