Biological Molecules

1. Biological Molecules

2. Making bonds • All bonds between subunits are formed in the same way • Condensation reaction • Removal of water H2O

3. Breaking bonds • All bonds between subunits are broken in the same way • Hydrolysis reaction • Addition of water H2O

4. Types of bonds • Glycosidic bonds – found between the monosaccharide subunits in disaccharides and poly saccharides • Peptide bonds – found between the amino acids that join to form dipeptides and polypeptides • Ester bonds – found between glycerol and fatty acids

5. Carbohydrates • Monosaccharides – reducing sugars • Disaccharides – mainly non-reducing sugars • Polysaccharides

6. Glucose Fructose Monosaccharides

7. Disaccharides • Maltose is formed from the condensation reaction between two glucose molecules

8. Sucrose (a non-reducing sugar) is formed from the condensation reaction between a glucose and a fructose molecule

10. Polysaccharides • Starch – energy storage molecule in plants • Glycogen – energy storage molecule in animals • Cellulose – structural molecule in plants

11. Starch • Starch is a good energy storage molecule • Starch molecules build up into compact starch grains in plant cells

12. Starch – molecular • Is made up of long chains of glucose molecules • Starch molecules can have many branches

13. Starch - structure to function • Because the molecules are branched they can form compact, almost spherical storage molecules • Insoluble in water – does not interfere with osmosis does not interfere with cell metabolism

14. Glycogen • Glycogen is the energy storage molecule in animals • Found mainly in the liver and muscles

15. Glycogen – structure to function • Very highly branched • Compact for storage • Branches means stored glucose can be released quickly

17. Cellulose – structure to function • Long unbranched chains of glucose • Straight chains linked by H bonds • Form microfibrils – strong fibres • Structural support in plant cell walls

19. Lipids • Lipids are fats oils and waxes • Made up of C H and O • Insoluble in water • Most fats and oils are triglycerides • Triglycerides composed of one molecule of glycerol and three fatty acids

20. Triglycerides - structure • Fatty acids may all be different • Joined the glycerol molecule by a condensation reaction • Ester bonds • Fatty acids tails are hydrophobic

21. Triglycerides – cont…. • Fatty acid tail may be saturated (no double –C=C- bonds) or unsaturated (some double –C=C- bonds)

22. Phospholipids • Phosphate group replaces one of the fatty acids • Ionised so make the head hydrophilic while tail remains hydrophobic • Important in cell membranes

24. Useful lipids • Medium/long term energy stores • Insulation • Buoyancy • Physical protection • Waterproofing • Source of water

25. Proteins • Subunit amino acids • Peptide bonds between amino acids • Primary, secondary, tertiary and quaternary structure • Fibrous and globular

29. Proteins structure and function • H bonds hold the secondary structure of proteins together • Tertiary structure held together by weak ionic bonds • Some proteins also contain disulphide bonds between certain amino acids

30. Globular proteins • Hydrophilic side chains on outside • Soluble • Easily transported in the blood • Metabolic activities • All enzymes • Haemoglobin

31. Fibrous proteins • Insoluble • Long polypeptide chains • Chains often tightly coiled • Structural found in supportive tissues • Collagen

33. Testing for biological molecules • Reducing sugars • Non-reducing sugars • Proteins • Lipids

34. Reducing sugars • Heat with Benedict’s solution • Positive result produces a coloured precipitate • Green, yellow, orange, brick red

35. Non-reducing sugars • Heat with Benedict’s solution • Negative result • Hydrolyse by heating with acid • Heat again with Benedict’s • Positive result

36. Starch • Add iodine solution • Positive result gives a blue black colour

37. Proteins • Add to buiret solution • (sodium hydroxide and copper sulphate) • Positive result give a lilac, mauve, purple colour

38. Lipids • Add ethanol to the sample • Shake and then pour the mixture into water • Positive result gives a white emulsion on the surface