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1.2 CARBOHYDRATES

1.2 CARBOHYDRATES. 1.1 WATER . 1.3 LIPIDS . MOLECULES OF LIFE. 1.5 NUCLEIC ACIDS . 1.4 PROTEINS . 1.3 LIPIDS. 2. 1.3 Lipids (1 hour). Objectives : State the types of lipids: fats, oils, phospholipids and steroids. Describe the structure of fatty acids and glycerols.

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1.2 CARBOHYDRATES

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  1. 1.2 CARBOHYDRATES 1.1 WATER 1.3 LIPIDS MOLECULES OF LIFE 1.5 NUCLEIC ACIDS 1.4 PROTEINS

  2. 1.3 LIPIDS 2

  3. 1.3 Lipids (1 hour) Objectives : • State the types of lipids: fats, oils, phospholipids and steroids. • Describe the structure of fatty acids and glycerols. • Describe the formation and breakdown of triglycerides.

  4. Triglycerides eg: Fats &Oils MAJOR TYPES OF LIPIDS Phospholipids eg: Lecithin Steroids eg: Cholesterol & Testosterone

  5. Organic molecules contain C, H, O but proportion of O is lower than in carbohydrates LIPIDS

  6. Molecules that are hydrophobic and insoluble in water (due to many hydrocarbons) But may dissolve in organic solvents (eg: acetone & benzene) LIPIDS

  7. Main types: triglycerides (fats & oils) phospholipids steroids LIPIDS

  8. The fats (solid at room temperature) & oils (liquid at room temperature) Also known as triacylglycerol Composed of 3 fatty acids & 1glycerol TRIGLYCERIDES * R = hydrocarbon chain

  9. A fatty acid (RCOOH) consists of a long linear hydrocarbon chain with a carboxyl group (-COOH) at one end Fatty Acids 9

  10. Fatty Acid Molecule Carboxyl group Long hydrocarbon chain O R HO C

  11. The fatty acid’s H-C chain is non-polar & hydrophobic causing triglycerides to be insoluble in water Fatty Acids 11

  12. Fatty acids can be classified as: i. Saturated fatty acid - no double bond in H-C chain - eg: stearic acid ii. Unsaturated fatty acid - 1 or more double bonds between carbons - a double bond produces a kink - eg: oleic acid

  13. A double bond; causing a kink

  14. Glycerols H • A type of alcohol • Aglycerolcontains 3 C & 3 hydroxyl (OH-) groups H C OH H C OH H C OH H 1 Glycerol

  15. Each fatty acid joins to glycerol by an ester bond Involves condensation Specifically for fats, the process is also known as esterification Triglyceride can be broken down by hydrolysis FORMATION & BREAKDOWN OF TRIGLYCERIDES

  16. FORMATION & BREAKDOWN OF TRIGLYCERIDE Ester bond condensation

  17. 3 FATTY ACIDS ESTER BOND + 3 H20 1 GLYCEROL 17

  18. Components of a triglyceride H O R 1 H C OH HO C O H C OH R 2 HO C O H C OH R 3 HO C H 3 fatty acids 1 Glycerol

  19. A triglyceride molecule H O R 1 H C O C O R 2 H C O C O R 3 H C O C H ester linkage

  20. Ester linkage A triglyceride

  21. The 3 fatty acids of 1 triglyceride may all be thesame orthey may bedifferent

  22. Triglycerides can be classified as: i. Saturated triglycerides (fats) - has 3 saturated fatty acids - in solid form at room temperature - eg: butter & most animal fats TRIGLYCERIDES

  23. ii. Unsaturated triglycerides (oils) - has 1 or more unsaturated fatty acids - in liquid form at room temperature (the kinks prevent the molecules from packing together closely to solidify) - eg: corn oil (plant fat) & cod liver oil (fish fat) TRIGLYCERIDES

  24. Major components of cell membranes Combination of: - 2 fatty acids - glycerol - phosphate group PHOSPHOLIPIDS

  25. PHOSPHOLIPIDS POLAR HEAD glycerol fatty acids NONPOLAR TAILS phosphate group Structure of phospholipid 26

  26. Phosphate group is –ve in charge A charged/polar additional molecule is usually attached to the phosphate group Causes the phospholipid to have a hydrophilic (polar) head The H-C chains of fatty acids form the hydrophobic (nonpolar) tails

  27. Many types of phospholipids (based on the fatty acids & additional molecule) Eg: lecithin (phosphatidylcholine) which has a choline group attached to the phosphate group PHOSPHOLIPIDS

  28. Phosphatidylcholine (a type of phospholipid)

  29. Lipids characterized by a carbon skeleton consisting of 4 fused rings Functional groups attached to the rings determine the types of steroids Eg: cholesterol & testosterone STEROIDS

  30. Cholesterol: - component of cell membranes - precursor for other steroids - may contribute to health problems (eg: atherosclerosis) cholesterol

  31. Testosterone: - male sex hormone (for sperm formation & male secondary sex characteristics)

  32. Fats as source of energy - 1 g of fat has twice as much energy as 1 g of a polysaccharide - due to the many C-H bonds in fat Fats & oils as energy storage Fats insulate the body against heat & electric Fats cushion vital organs Fats provide buoyancy Fats transport fat-soluble vitamins (A,D,E,K) IMPORTANCE OF LIPIDS

  33. 7. Phospholipids & cholesterols as components of cell membranes Cholesterols as precursor for other steroids 9. Steroids as sex hormones IMPORTANCE OF LIPIDS

  34. SESSION 2001 / 2002 Question Explain the triglyceride structure. [6 marks]

  35. References : Campbell, 8th edition Solomon, 9th edition

  36. Next Subtopic…. 1.2 CARBOHYDRATES 1.1 WATER 1.3 LIPIDS MOLECULES OF LIFE 1.5 NUCLEIC ACIDS 1.4 PROTEINS 1.4 Proteins 37

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