Lipids
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Lipids

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Lipids Lipids Presentation Transcript

  • Lipids are: water-insoluble organic substances but readily soluble in organic solutions e.g. ether
  • The term ‘lipid’ defines compounds: • not on the basis of structural similarity BUT • in terms of their solubility
  • Water is so attracted to other water molecules that anything between them is squeezed out of the way. ‘’;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;
  • Lipids do not form polymers. Why? Not made of monomers. Lipids are: structurally functionally DIVERSE
  • Types of Lipid 1. Triglycerides [Fats & Oils] 2. Waxes 3. Phospholipids 4. Steroids 5. Glycolipids 6. Lipoproteins 7. Terpenes
  • Types of Lipid 1. Triglycerides [Fats & Oils] 1. 2. 3. 4. 5. 6. Waxes Phospholipids Steroids Glycolipids Lipoproteins Terpenes
  • 1. Fats & Oils • the commonest lipids in nature • the constituents of fats are:- glycerol (propane 1-2-3 triol) fatty acids (alkanoic acids)
  • i) Fatty acids - general formula: R.COOH - most have an even number of C - most commonly 16-18 - fatty acids may be:  saturated or unsaturated R C16H32O2
  • Saturated fatty acid [Single bonds only] Unsaturated fatty acid [Double bonds]
  • Stearic acid, C17H35COOH – Saturated fatty acid Oleic acid, C17H33COOH – Unsaturated fatty acid
  • The more double bonds present, the more bent the molecule is
  • What is the difference between a fat and an oil?  fats - solid at 20C  oils - liquid at 20C
  • Why are fats solid and oils liquid at room temperature? Molecule has kinks, keeping the fatty acids apart and as a result, oil is liquid at room temperature.
  • A glyceride forms when an –OH in glycerol is replaced by an organic acid glycerol Fatty acid
  • Types of glycerides: Monoglyceride Diglyceride Triglyceride
  • Why are fats and oils classified as triglycerides?
  • Triglycerides: - are non-polar and float on water Non-polar tail Hydrophobic Polar head Hydrophilic
  • Animal fat solidifies at a low temperature
  • Why do plants and poikilotherms tend to have a high proportion of unsaturated fatty acids? To prevent their triglycerides from solidifying.
  • Fatty acids link to glycerol as a water molecule is lost
  • Fats & oils are made of one glycerol and three fatty acids
  • Formation of a triglyceride formed by esterification / condensation
  • Fatty acids may be different in a triglyceride
  • Functions of Triglycerides 1. Store energy in animals + Yield energy
  • Comparison of energy yield from: Triglycerides: 37 kJ g-1 Carbohydrates: 17 kJ g-1 MORE energy from triglycerides: Due to more hydrogen.
  • 2. Animals store extra fat when hibernating: acts as an insulator. Subcutaneous fat
  • 2. Fat around organs:  protect against bumps  keeps them warm Kidney surrounded by fat
  • 3. Brown adipose tissue (brown fat) - releases heat but no ATP - heat maintains core temperature in:  small mammals  in newborn humans, particularly during cold exposure without shivering
  • 4. In aquatic mammals blubber contributes to buoyancy.
  • What is present in the hump? Why? FAT When fat is metabolised, it yields: 1. energy 2. more than 1 g of water for each 1 g of fat by respiration.
  • 5. Water is produced when fats are oxidised - this metabolic water is important in desert animals. 1. Eating 2. Metabolism A kangaroo rat never drinks. Mention TWO ways how it can get water.
  • 6. Nerves are covered with a myelin sheath for insulation of the fibre and for fast conduction of impulses.
  • Test for Triglycerides Paper becomes translucent.
  • Chemical Test for Triglycerides Sudan III
  • Chemical Test for Triglycerides Emulsion Test
  • Types of Lipid 1. Triglycerides [Fats & Oils] 2.Waxes 3. Phospholipids 4. Steroids 5. Glycolipids 6. Lipoproteins 7. Terpenes
  • Waxes: not a food source no enzymes to break them down
  • Structure of Waxes one fatty acid an alcohol of high molecular weight instead of glycerol
  • Feathers do not get wet – WHY? Raindrops on feathers.
  • Waxes are mainly for e.g. cutin makes up the waxy cuticle of leaves fruits produce a waxy coating to keep from drying out
  • sebum in mammalian skin
  • wax in ears traps: dust sand other foreign particles do not go deeper into the ear and cause no damage
  • suberin in Casparian strips,
  • exoskeleton in insects [contains wax]
  • waxes build elaborate structures such as beehives
  • Types of Lipid 1. Triglycerides [Fats & Oils] 2. Waxes 3.Phospholipids 4. Steroids 5. Glycolipids 6. Lipoproteins 7. Terpenes
  • Phospholipids • lipids with a phosphate group
  • Phospholipids are made of one phosphate group and 2 fatty acids Phospholipids are amphipathic – have both polar & nonpolar portions
  • • constituents of membranes
  • Two structures formed by self-assembly of phospholipids in aqueous environments
  • Types of Lipid 1. Triglycerides [Fats & Oils] 2. Waxes 3. Phospholipids 4.Steroids 5. Glycolipids 6. Lipoproteins 7. Terpenes
  • Steroids are structurally different from all other lipids consist of a complex carbon ring structure Cholesterol is a steroid.
  • Cholesterol: • is the steroid present in the largest amount in humans • a key intermediate in the synthesis of related steroids • an important constituent of animal plasma membranes made in the liver
  • Sex hormones are Steroids
  • Types of Lipid 1. Triglycerides [Fats & Oils] 2. Waxes 3. Phospholipids 4. Steroids 5.Glycolipids 6. Lipoproteins 7. Terpenes
  • Glycolipids • carbohydrate + lipid • components of cell membranes
  • Types of Lipid 1. Triglycerides [Fats & Oils] 2. Waxes 3. Phospholipids 4. Steroids 5. Glycolipids 6.Lipoproteins 7. Terpenes
  • Lipoproteins • occur in membranes • are the form in which lipids are transported in the blood e.g. fatty acids are bound to albumin protein triglyceride & cholesterol phospholipid Lipoproteins vary in size and composition
  • Types of Lipid 1. Triglycerides [Fats & Oils] 2. Waxes 3. Phospholipids 4. Steroids 5. Glycolipids 6. Lipoproteins 7.Terpenes
  • Terpenes may be: volatile : attract pollinators less volatile: strongly bitter-tasting to prevent plants being eaten by herbivores
  • Examples of terpenes: rubber carotenoids  light-absorbing pigments in animals & plants
  • β carotene: - traps light in plants and in humans - is broken down into two vitamin A molecules from which we make rhodopsin
  • Carotenoids also act as antioxidants:  trap free radicals and inhibit oxidation Free radicals:  highly unstable molecules  that attack healthy cells  through a damaging chain reaction of oxidation.
  • Antioxidants:  prevent cancer  improve the immune system
  • Question: [MAY, 2007] Suggest explanations for the following statement. Fats are used as storage molecules rather than as an immediate energy source. (2) Fats are ideal for storing energy as they release large quantities of energy. This means that small quantities of stored fat carried by the organism provide sufficient energy without having to carry a heavy load. Fat molecules are large and would take a long time to release energy, making them unsuitable for immediate sources of energy.
  • Question: [SEP, 2007] Use your knowledge of biology to explain the following. (5 marks) Most animals use fats, rather than starch, as energy-storage molecules.
  •    No life as we know it can exist without lipids. Comment on the importance of lipids to life. [1994] Give an account of the important roles played by lipids in living organisms. [SEP, 1998] Give an overview of the importance of lipids for living organisms. [SEP, 2009]