Monosaccharides are single sugars.
Pentoses contain five carbon atoms; they occur in nucleic acids.
Hexoses contain six carbon atoms.
α-glucose is the most common respiratory substrate.
Disaccharides are formed by condensation between two monosaccharides.
Maltose consists of two α-glucose molecules linked by a 1,4 glycosidic bond.
Polysaccahrides are macromolecules. They are polymers formed from many monosaccharides joined by glycosidic bonds.
Starch (plants) and glycogen (animals) are formed from condensation between hundreds of α-glucose molecules. Starch and glyogen are osmotically inactive, compact molecules so are good storage molecules.
Cellulose (plants) consists of hundreds of β-glucose molecules. The fibrous nature of cellulose gives strength to cell walls.
LIPIDS
A triglyceride molecule consists of three fatty acids linked to glycerol by ester bonds.
The ester bonds are formed by condensation.
A phospholipid molecule has two fatty acids and one phosphate group linked to a molecule of glycerol.
PROTEINS
Proteins are macromolecules. They are polymers consisting chains of amino acids linked by peptide bonds formed by condensation.
The sequence of amino acids is the primary structure of the protein.
The secondary structure is the coiling of the primary structure into α-helix or folding into β-sheets. It is held by hydrogen bonds.
The tertiary structure is the final shape of the molecule, held together by disulphide bridges and ionic bonds.
The quartenary structure is when the different polypeptides associate with each other.
MACROMOLECULE means giant molecules.
Three types of macromolecules:
- Polysaccharides
- Proteins (Polypeptides)
- Nucleic Acid (Polynucleotides)
