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Chapter 5: Biological Molecules

Chapter 5: Biological Molecules. Carbon based compound Consist of C, H, O atoms Sometimes P, N, S atoms Properties depends on : Arrangement of carbon skeleton Functional group. Functional groups. Def : the component of the organic molecules that commonly involved in chemical reactions.

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Chapter 5: Biological Molecules

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  1. Chapter 5: Biological Molecules • Carbon based compound • Consist of C, H, O atoms • Sometimes P, N, S atoms • Properties depends on : • Arrangement of carbon skeleton • Functional group

  2. Functional groups • Def : the component of the organic molecules that commonly involved in chemical reactions. • Usually located at the terminal of molecules structure • Provide a unique properties to molecules

  3. Carbonyl Hydroxyl groups Carboxyl groups FUNCTIONAL GROUPS Amino groups Sulfhydryl groups Phosphate groups

  4. a) Hydroxyl groups • Hydrogen atoms bonded to oxygen atom • Located at one end of the carbon skeleton • Called alcohols • Specific names end in – ol • Eg : Propanol, Ethanol

  5. H H C OH H H H H C C OH H H Methanol Ethanol H H H H C C C H H OH H 2-Propanol

  6. Functional properties • Polar • Electronegative oxygen atom drawing electrons toward itself • Attract water molecules, help to dissolve organic compounds. • Eg : Sugar

  7. b) Carboxyl group • When an oxygen atom is double-bonded to a carbon atom that is also bonded to a hydroxyl group. • - COOH • Compound with carboxyl groups : Carboxylic acid or Organic acid

  8. H O H C C OH H Acetic acid

  9. Functional properties • Act as source of Hydrogen ions (H+) • Acidic properties • The covalent bond between O and H • So polar • H+ ions tend to dissociate reversibly

  10. c) Carbonyl group • Consist of carbon atom joined to an oxygen atom by a double bond • - CO • Known as ketones • If the carbonyl group is within a carbon skeleton • Known as aldehydes • If the carbonyl group is at the end of skeleton

  11. H O H H C C C H H H H H O H C C C H H H Acetone (ketone) Propanal (Aldehyde)

  12. Functional properties • Ketone and aldehyde is a structural isomer with different properties

  13. d) Amino groups • Consists of a nitrogen atom bonded to two hydrogen atom and to the carbon skeleton • - NH2 • Known as amines • Eg : Amino acid

  14. H H O N C C OH H H Glycine

  15. Functional properties • Acts as a base • Able to pick up proton from surrounding H H N N H H H Non-ionized ionized

  16. e) Sulfhydryl groups • Consists of a sulfur atom bonded to an atom of hydrogen • Resemble a hydroxyl group in shape • - SH • Known as thiols • Eg : Ethanethiol

  17. H H H C C SH H H Ethanethiol

  18. Functional properties • 2 sulfhydryl groups can interact to help stabilize protein structure

  19. f) Phosphate group • Phosphorus atom is bonded to four oxygen atoms • - OPO32- • It is an ionized form of a phosphoric acid group ( - OPO3H2) • Known as organic phosphate

  20. OH OH H O H C C C O P O- H H H O- Glycerol phosphate

  21. Functional properties • Makes the molecule of which it is a part an anion (negatively charge ion) • Able to transfer energy between organic molecules

  22. MACROMOLECULE

  23. Macromolecules • Known as large molecules : chain-like molecules • Called polymers • Long molecules consisting of many similar or identical building block • Linked by covalent bond • Form by monomers

  24. Biological molecules • Carbohydrates • Lipid • Protein • Nucleic acid

  25. CARBOHYDRATES

  26. Carbohydrates • Include sugar and polymers of sugar • The simplest carbohydrates : Monosaccharides (simple/single sugar) • Disaccharides : double sugars (2 monosaccharides joins by condensation reaction)

  27. Polysaccharides (polymers composed of many sugar building blocks) • Eg : Carbohydrates

  28. Monosaccharides • From the Greek words, Monos : single and Sacchar : sugar • Three types; glucose,galactose,fructose • Generally have molecular formula that are multiple of unit CH2O • Glucose, C6H12O6 – common monosaccharides • Contain a carbonyl group and multiple of hydroxyl groups

  29. The structure and classification of some monosaccharides : • Location of carbonyl group • Length of carbon skeleton • Spatial arrangement around asymmetric carbons

  30. Sugar is either aldose or ketose, depending on the location of carbonyl group • Glucose and Galactose – aldose • Fructose – ketose • The size of carbon skeleton (range from 3 to 7) • 6-carbon sugar : Hexose • 5-carbon sugar : Pentose

  31. Spatial arrangement of the parts around asymmetric carbon. • Asymmetric carbon : • Carbon attached to 4 different kinds of partner • Eg : Glucose and Galactose

  32. Glucose Galactose

  33. Glucose can be divide into 2 part : • Depends on the location of the Hydroxyl group at carbon 1 • Known as : • Hydroxyl up – β (Beta) • Hydroxyl down – α (Alpha)

  34. In aqueous solution, glucose molecules form ring structure

  35. Dissacharides • Consists of 2 monosaccharides joined by a glycosidic linkage • Glycosidic linkage – covalent bond formed by dehydration reaction • Eg : Maltose Glucose + Glucose Sucrose Glucose + Fructose

  36. Maltose Glucose Glucose

  37. Polysaccharides • Macromolecules • Consists of few hundred to a few thousand of monosaccharides • Link by glycosidic linkage • The process known as condensation (eliminates water) • Serve as : • Storage material • Building material

  38. Storage material: • Starch (plants) • Glycogen (animals)

  39. Storage material • Starch • Storage polysaccharides for plants • Consists entirely glucose monomers • Mostly joined by α (1-4) linkages • The angle – formed polymer helical • Type of starch : • Amylose • Amylopectin

  40. Amylose • The simplest form of starch • Unbranched • Amylopectin • More complex form • Branched polymer • 1-6 linkages at the branch point

  41. Amylose

  42. amylopectin

  43. Animal stored polysaccharides – Glycogen • Polymer resemble amylopectin but more extensively branched • Branch linkages every 8 – 10 residues • Human and vertebrates stored glycogen in liver and muscle cells

  44. Building materials; • Cellulose • Chitin

  45. Building material- cellulose • Known as structural polysaccharides • Eg : Cellulose • Major component of the tough walls that enclose plant cells • Polymer of glucose but the glycosidic linkages is different from starch

  46. When glucose form a ring, the hydroxyl group attached to num 1 carbon is positioned either below or above the plane • Glucose monomer in cellulose are all in β configuration

  47. Cellulose molecule is straight • Unbranched • The hydroxyl group free to hydrogen bonded with the hydroxyl group of other cellulose • In plant cell walls, parallel cellulose held together forming microfibrils • Can be digested by cellulase enzyme

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