biologicalmolecules.pptxxxxxxxxxxxxxxxxxx

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1. BIOLOGICAL MOLECULES ALBIO9700/2006JK The structure of carbohydrates, lipids and proteins and their roles in living organisms

2. Molecular biology : the study of structure and functioning of biological molecules Metabolism : the sum total of all the biochemical reactions in the body The building blocks of life : Hydrogen, carbon, oxygen and nitrogen Monosaccharides , organic bases, amino acids, fatty acids and glycerol ALBIO9700/2006JK

3. Macromolecule : ‘giant molecule’ Polymers (cellulose & rubber; polyester, PVC & nylon): macromolecules made up of many repeating subunits that are similar or identical to each other and are joined end to end ( polymerisation ) Polysaccharides Proteins (polypeptides) Nucleic acids (polynucleotide) ALBIO9700/2006JK

4. Carbohydrates Contains carbon, hydrogen and oxygen General formula: C x (H 2 O) y 3 main groups: Monosaccharides Disaccharides Polysaccharides ALBIO9700/2006JK

5. Monosaccharides Sugars ( saccharide ~ sweet or sugar) General formula: (CH 2 O) n Molecular and structural formula Single sugar molecule ( mono ) Types: Trioses (3C) Pentoses (5C) Hexoses (6C) ALBIO9700/2006JK

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7. Ring structures α -glucose : the form of glucose where the hydroxyl group (-OH) on carbon atom 1 is below the ring β -glucose : the form of glucose where the hydroxyl group (-OH) on carbon atom 1 is above the ring Isomers : 2 forms of the same chemical ALBIO9700/2006JK

8. Roles of monosaccharides in living organisms Source of energy in respiration (glucose) Due to large number of carbon-hydrogen bonds which can be broken to release energy Building blocks for larger molecules Glucose: make polysaccharides (starch, glycogen and cellulose) Ribose (a pentose): make RNA and ATP Deoxyribose (a pentose): used to make DNA ALBIO9700/2006JK

9. Sugars Condensation : how 2 monosaccharides join together to form disaccharides Bridge is called glycosidic bonds Hydrolisis : addition of water, reverse of condensation (during digestion of disaccharides and polysaccharides) Both controlled by enzymes ALBIO9700/2006JK Disaccharides and glycosidic bond

10. ALBIO9700/2006JK Condensation Hydrolisis

11. Polysaccharides Not sugars Polymers with monosaccharide subunits joined by condensation with glycosidic bonds Several thousand monosaccharide units join to form a macromolecule Most important polysaccharides: Starch Glycogen Cellulose ALBIO9700/2006JK Polymers of glucose

12. Glucose is converted to storage polysaccharides which are convenient, compact, insoluble molecules In the form of starch in plants and glycogen in animals ALBIO9700/2006JK

13. Starch, Glycogen and Cellulose Starch is a mixture of amylose and amylopectin Amylose : many 1,4-linked α -glucose molecules form a spring like compact structure Amylopectin : 1,4-linked α -glucose but shorter chains with branching out due to 1,6 linkages Starch grains commonly found in chloroplast and in storage organs such as the potato tuber and the seeds of cereals and legumes ALBIO9700/2006JK

14. Amylose ALBIO9700/2006JK

15. Amylopectin ALBIO9700/2006JK

16. Glycogen No starch in animal cells Glycogen: amlyopectin -like molecules used as the storage carbohydrates Glycogen molecules tend to be more branched than amylopectin They clump together to form granules – liver cells and muscle cells ALBIO9700/2006JK

17. Glycogen ALBIO9700/2006JK

18. Cellulose Most abundant organic molecule (20-40% of the average cell wall) Structural role (mechanically strong) Cellulose is a polymer of β -glucose Hydrogen bonds Microfibrils Fibrils ALBIO9700/2006JK

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21. Very high tensile strength (almost equal to steel) Provide support by making tissues rigid Responsible for cell expansion during growth Freely permeable , allowing water and solutes to reach plasma membrane ALBIO9700/2006JK

22. Lipids Diverse group of chemicals Triglycerides – most common type Commonly fats and oils ALBIO9700/2006JK

23. Triglycerides 3 fatty acid + 1 glycerol ( condensation ) -COOH group attached to a hydrocarbon tail Glycerol – alcohol Glyceride – fatty acid + glycerol ( triglyceride ) ALBIO9700/2006JK

24. ALBIO9700/2006JK Condensation

25. Insoluble in water but soluble in organic solvent (ether, chloroform and ethanol) Due to hydrocarbon tail of fatty acids Non-polar and hydrophobic ALBIO9700/2006JK

26. Saturated and unsaturated fatty acids ALBIO9700/2006JK

27. Unsaturated – do not contain the maximum possible amount of hydrogen Fatty acids and lipids melt easier due to double bonds Polyunsaturated - >1 double bond Monounsaturated - 1 double bond Animal lipids – saturated (fats) Plant lipids – unsaturated (oils) ALBIO9700/2006JK

28. Roles of triglycerides Energy reserves (richer in carbon-hydrogen bonds than carbohydrates/higher calorific value) Insulator against loss of heat Buoyancy Metabolic source of water ALBIO9700/2006JK

29. ALBIO9700/2006JK Desert kangaroo rat

30. Phospholipids One end is soluble in water One of the 3 fatty acids is replaced by a phosphate group which is polar Phosphate group is hydrophilic Membrane structure ALBIO9700/2006JK

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32. Proteins >50% of the dry mass of most cells is protein Functions: Essential components of cell membranes The oxygen-carrying pigment haemoglobin Antibodies which attack and destroy invading microorganisms All enzymes Hair and the surface layers of skin contain the protein keratin Collagen adds strength to the many tissues, such as bone and the walls of arteries ALBIO9700/2006JK

33. Amino acids Basic component of protein Central carbon atom, amine group (-NH 2 ), carboxylic acid group (-COOH) R group 20 different amino acids ALBIO9700/2006JK

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35. ALBIO9700/2006JK The eight amino acids in the orange area are nonpolar and hydrophobic. The other amino acids are polar and hydrophilic ("water loving"). The two amino acids in the magenta box are acidic (" carboxy " group in the side chain). The three amino acids in the light blue box are basic ("amine" group in the side chain).

36. The peptide bond ALBIO9700/2006JK

37. 2 linked amino acids – dipeptide Many amino acids – polypeptide (macromolecule/polymer) Ribosomes – sites where amino acids are linked together to form polypeptides Complete protein may contain one or more polypeptide chain which interact with each other ALBIO9700/2006JK

38. Primary structure The types of amino acids contained in the polypeptide chain and the sequence in which they are joined Enormous number of different possible primary structures ALBIO9700/2006JK

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40. Secondary structure Polypeptide chain coils into an α -helix due to attraction between the oxygen of the -CO group of one amino acid and the hydrogen of the -NH group of the amino acid four places ahead of it This is result of the polar characteristics of the –CO and –NH groups Sometimes a much looser, straighter shape is formed, called a β -pleated sheet ALBIO9700/2006JK

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42. Tertiary structure The secondary structure coils and folds to form 3 dimensional shapes Four types of bonds involved: Hydrogen bonds (between R groups) Disulphide bonds (between 2 cysteine molecules) Ionic bonds (between R groups containing amine and carboxyl groups) Hydrophobic interactions (between R groups which are non-polar or hydrophobic) ALBIO9700/2006JK

43. Tertiary structure ALBIO9700/2006JK

44. Quaternary structure ALBIO9700/2006JK

45. Globular protein : protein whose molecules curl up into a ‘ball’ shape (e.g. myoglobin & haemoglobin ) Usually curl up so that their non-polar, hydrophobic R groups point into the centre of the molecule, away from their watery surroundings. The polar, hydrophilic, R group remain on the outside of the molecule Fibrous protein : long strands, insoluble and have structural roles (e.g. keratin & collagen) ALBIO9700/2006JK Globular and fibrous proteins

46. Globular and fibrous proteins ALBIO9700/2006JK e.g. enzymes e.g. keratin and collagen

47. Molecular structure and function of haemoglobin as an example of a globular protein Molecular structure and function of collagen as an example of a fibrous protein ALBIO9700/2006JK

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