Biological molecules

• Most carbohydrates, proteins and nucleic acids are polymers which consist of monomers
• Monomers are smaller molecules such as monosaccharides, amino acids and nucleotides
• Polymers form during condensation reactions and are broken down during hydrolysis

Sugars

• All carbohydrates contain C, H and O
• Carbohydrates can consist of glucose, fructose and galactose
• Disaccharides such as maltose, lactose and sucrose are made from these monosaccharides using glycosidic bonds
• Benedicts test - used for identifying reducing sugars (all but sucrose). Benedicts solution is mixed with the sample and heated, if it changes colour a reducing sugar is present but if it stays the same a non reducing sugar may be present. To see repeat with a new sample and add HCL, if it changes a non-reducing sugar is present

Polysaccharides

• Starch - Excess alpha glucose is stored as starch in plants as amylose (chain) or amylopectin (branched). Its also insoluble so osmosis is unaffected.
• Glycogen - Animals store excess alpha glucose as glycogen in a branched structure. This allows it to be broken down quickly for fast energy release.
• Cellulose - Made of beta glucose and forms straight chains which are linked by hydrogen bonds to form microfibrils. They have a lattice structure for strength
• Iodine test for starch - Orange-no starch, black/blue-starch

Lipids

• Made from glycerol and 3 fatty acid hydrocarbon chains
• Saturated fatty acids have no double bonds
• unsaturated fatty acids have at least one double bond
• Triglycerides form in condensation reactions joined by ester bonds
• Lipids in membranes are phospholipids rather than triglycerides so they have a phosphate…