1. monosaccharides are polymers of (CH2O)n;
2. polysaccharide are chains of monosaccharides i.e. they are polymer of polymers.
| sugar | no. of CH2O |
| triose | 3 |
| tetrose | 4 |
| pentose | 5 |
| hexose | 6 |
Hexoses are alcohols with additional aldehyde or keto group.
If they have a an aldehyde group they are called aldoses, if the keto group is present we refer to them as ketoses.
All hexoses undergo cyclization. Linear structure forms a ring structure bridged by an oxygen.
Hexose which is a ketose makes a 5-membered ring (fructose) while aldoses make a 6-membered ring: (glucose).
Sugar rings are predominantly planar with the hydrogen and hydroxide groups sticking below and above the plane of the ring
Depending whether OH group of the first carbon in the ring is below or above the ring we talk about a and b forms. In solution glucose undergoes rapid transformation between a and b forms via a straight chain conformation.
sucrose = glucose + fructose
Condensation of glucose and fructose is accomplished by extraction of water molecule from the two -OH to form oxygen bridge between the monosaccharide units. Such a bridge is called glycosidic bond.
Condensation and hydrolysis reactions are make-and-brake reactions of the cellular metabolism.
The oxygen bridges can be formed between C1and C4 or C1 and C6 of neighboring sugars units. The accompanying numbers identify the bridged carbons and the placement of the O-bridge with respect to the ring plane
It consists of two different polymers of glucose: amylose and amylopectin.
Amylose is made of a straight glucose chain with the glycosidic bonds between C1 and C4 of neighboring molecules. The glucose is in a form forming an O-bridge above the polysaccharide chain. Amylose curls up into a helix stabilized by hydrogen bonds.
Amylopectin is similar to amylose but in addition to a 1-4 links it contains branch points formed by a 1-6 links every 6 glucose residues.
Its structure is the same as for amylopectin but more branched.
Cellulose is made of straight chains of b 1-4 linked glucose residues. The b linkage forces alternate placement of glucose rings.
Such an arrangement of glucose residues allows for hydrogen bonding between neighboring cellulose chains. This pattern of intermolecular H-bonds gives cellulose its structural rigidity.
information transfer: hormones
energy storage: fat
Fatty acids make spherical micelles in water, tails forming the inside while polar heads stick out on the surface.
Adipose tissue is made primarily of tri-acylglycerols (fat).
Two fatty acid chains are joined to glycerol backbone, the third hydroxyl of glycerol has phospho- derivative of sugars, amines, a variety of groups often charged constituting polar head.
Heads are often zwitterions: they have both +ve and -ve charge.
Phospholipids make in water a bilayer sandwich: heads out - acyl chains in. Bilayer sandwich is a basic component of cell membranes.
Cholesterol: most common of the steroids, part of membranes, precursor of hormones.
Testosterone: male sex hormone
Progesterone: female sex hormone