Biological Molecules

AS Biology, Biological Molecules Revision Notes

Distinguish between monomers and polymers:

Monomers- Identical small molecules.
Polymers- Chainlike molecules formed from the linking together of many similar.

Distinguish between monosaccharides, disaccharides, and polysaccharides:

Monosaccharides- Simple sugars; sugar molecules may be enantiomers due due to the spatial arrangement of parts around asymmetric carbons; raw material for synthesis of other organic molecules.
Disaccharides- Two monosaccharides that are joined by a glycosidic linkage.
Polysaccharides- Storage or structural macromolecules made from a few hundred to a few thousand monosaccharides.

Formation of glycogen and cellulose by condensation reactions to form glycosidic bonds:
These are formed when two monosaccharides are condensed together. One monosaccharide loses an H atom from carbon atom number 1 and the other loses an OH group from carbon 4 to form the bond.
The reaction, which is called a condensation reaction, involves the loss of water (H2O) and the formation of an 1,4-glycosidic bond. Depending on the monosaccharides used, this can be an α-1,4-glycosidic bond or a β-1,4-glycosidic bond.

The reverse of this reaction, the formation of two monosaccharides from one disaccharide, is called a hydrolysis reaction and requires one water molecule to supply the H and OH to the sugars formed.

Triglyceride & Phospholipids difference:
Phospholipids and triglycerides are both composed of fatty acids attached to a molecule called glycerol. A glycerol molecule can have up to three fatty acids attached, and the glycerol molecule of triglycerides contains the maximum of three fatty acids. Since fatty acids are hydrophobic -- "water-hating" -- molecules, triglycerides cannot dissolve in water. By contrast, the glycerol molecule of phospholipids has only two fatty acids attached. A molecule with an electrical charge occupies the third position of glycerol in phospholipids. The charged molecule is hydrophilic, or water-loving. Thus, phospholipids can dissolve in both water and fats and are known as emulsifiers. They can help disperse hydrophobic molecules such as triglycerides and cholesterol in watery fluids, including the blood.

Group
Building Block
Large Molecule
Function
To Identify, Look for . . .
Carbohydrate
Monosaccharide
Polysaccharide
Energy storage, receptors, structure of plant cell wall
Made of C,H, and O; –OH's on all carbons except one
Protein
Amino acid
Polypeptide or protein
Enzymes, structure, receptors, transport, and more
Contain N, have N-C-C backbone
Nucleic acid
Nucleotide
Polynucleotide or nucleic acid
Information storage and transfer
Contain N in rings, nucleotides made of sugar, phosphate and nitrogenous base
Lipid
Glycerol, fatty acids
Fats, oils, waxes, phosopholipids, steroids
Membrane structure, energy storage, insulation
Made of C,H, and O; lots of C-H bonds; may have some C=C bonds (unsaturated); steroids have 4 rings