3.1 Biological molecules

• The smaller units from which larger molecules are made
• Define "polymers""" Molecules made from a large number of monomers joined together
• Define "isomers""" Molecules with the same molecular formula but a different molecular structure
• Carbohydrate monomer Monosaccharide
• Protein monomer Amino acid
• Nucleic acid monomer Nucleotide
• Carbohydrate polymer Polysaccharide
• Protein polymer Proteins + polypeptides
• Nucleic acid polymer DNA
• Define "peptide""" The bond formed between 2 amino acids
• What is a condensation reaction? A reaction that joins 2 molecules together with the formation of a chemical bond and involves the elimination of a molecule of water
• Define "monosaccharides""" The monomers from which larger carbohydrates are made
• Examples of common monosaccharides Glucose, galactose, fructose
• Define "glycosidic bond""" The bond formed by the condensation reaction between two monosaccharides
• How are disaccharides formed? The condensation of two monosaccharides
• Disaccharide formed by condensation of 2 glucose molecules Maltose
• Disaccharide formed by condensation of a glucose molecule and a fructose molecule Sucrose
• Disaccharide formed by condensation of a glucose molecule and a galactose molecule Lactose
• How are polysaccharides formed? The condensation of many glucose units
• What polysaccharides are formed by the condensation of α-glucose? Glycogen + starch
• What polysaccharide is formed by the condensation of β-glucose? Cellulose
• Define "condensation reaction""" A chemical reaction between 2 molecules where there is the elimination of water (or another simple molecule)
• Define "hydrolysis reaction""" A chemical reaction where water is used to break a bond within a substance
• How are polymers and disaccharides broken down into monomers? Hydrolysis reaction
• What is starch? Storage polysaccharide found in plants
• Where are large amounts of starch found? Seeds, storage organs e.g. potato tubers
• What are the 2 molecules that make up starch & their proportions? Amylose ~25% Amylopectin ~75%
• What monomer makes up starch? Alpha glucose
• What type of bond joins the glucose monomers in amylose? alpha 1,4 glycosidic linkages
• Amylose structure - Long, linear, unbranched chain - Helical 3D structure, coiled like a spring - 6 glucose monomers per turn
• Why is amylose an excellent storage molecule? Its coiled structure makes it highly compact
• What types of bonds join the glucose monomers in amylopectin? alpha 1,4 glycosidic bonds with occasional alpha 1,6 glycosidic bonds
• Amylopectin structure Long branched chain
• What is the benefit of amylopectin chains being branched? The branches provide many exposed ends, so many enzymes can act on them simultaneously, so it is hydrolysed faster so glucose can be released more quickly
• How is starch adapted for storage? - Insoluble so doesn't affect water potential of surrounding cells - Large and insoluble so doesn't diffuse out of cells - Compact - When hydrolysed forms alpha glucose which is easily transported and readily used in respiration - Amylopectin branched
• What is glycogen? Energy (glucose) storage polysaccharide in animals
• What monomer makes up glycogen? alpha glucose
• What bonds join the monosaccharides in glycogen? Alpha-1.,4 and alpha-1,6 (more 1,6 than in amylopectin)
• What is the benefit of glycogen being branched? More branching = more ends that can be acted on simultaneously by enzymes, so more easily broken down into glucose monomers for higher rate of respiration in animals
• How is glycogen structurally adapted for storage? - Insoluble so does not affect water potential of surrounding cells - Insoluble so does not diffuse out of cells - Compact - More highly branched than starch