Lipids 3.1.3

  • Created by: madii
  • Created on: 22-09-17 17:31
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  • Lipids
    • like carbohydrates contain carbon, hydrogen and oxygen only but have a higher H:O ratio
    • non-polar and cannot dissolve in water
      • can dissolve in non-polar solvents such as alcohol
    • Triglycerides
      • formed when a glycerol molecule condenses, and combines, with three fatty acid molecules
        • bonds between glyerol and fatty acids known as ester bonds
        • glycerol has formula C3H8O3
          • soluble in water due to polar OH groups
        • different triglycerides formed depending on fatty acids
        • Fatty acid is a long chain hydrocarbon attached to a carboxyl group
          • saturated - no double bonds
            • increase levels of cholesterol in blood and lead to atherosclerosis
              • atherosclerosis is the narrowing of arteries due to build up of fatty deposits
          • unsaturated - double bond, one is mono-unsaturated more is poly-unsaturated
          • as humans we are capable of making some fatty acids but others we can't
            • therefor it is essential we eat these within triglycerides  and they are known as essential fatty acids
              • Triglycerides
                • formed when a glycerol molecule condenses, and combines, with three fatty acid molecules
                  • bonds between glyerol and fatty acids known as ester bonds
                  • glycerol has formula C3H8O3
                    • soluble in water due to polar OH groups
                  • different triglycerides formed depending on fatty acids
                  • Fatty acid is a long chain hydrocarbon attached to a carboxyl group
                    • saturated - no double bonds
                      • increase levels of cholesterol in blood and lead to atherosclerosis
                        • atherosclerosis is the narrowing of arteries due to build up of fatty deposits
                    • unsaturated - double bond, one is mono-unsaturated more is poly-unsaturated
                    • as humans we are capable of making some fatty acids but others we can't
                      • therefor it is essential we eat these within triglycerides  and they are known as essential fatty acids
      • Waxes
        • lipid molecules which have single hydrocarbon chains linked to an alcohol other than glycerol
        • not digested by animals
        • waterproof coverings in living organisms
          • insects chitin skeletons are covered in waxy layer
            • prevent water loss and dehydration
              • leaves have waxy cuticle
          • leaves have waxy cuticle
      • Steroids
        • lipids with highly , complex molecules, form basis of many hormones
        • cholesterol is a well known steroid
          • although it is thought as dangerous it is an essential molecule in living organisms
          • found in cell membranes where it performs an integral structure role
          • made in the liver and is also supplied in diet
      • Phospholipids
        • similar structure to triglyceride molecules
          • however one fatty acid is replaced with a phosphoric acid molecule
            • hydrophilic phosphate molecule contains OH groups which is attracted to polar water molecules
            • rest of molecule is non-polar thus is hydrophobic
              • therefor in water, phospholipids molecules automatically orientate themselves so fatty acid tail avoids water and phosphate heads are directed towards it
                • hydrophilic phosphate molecule contains OH groups which is attracted to polar water molecules
                • this maintains cell membrane structure as there are two layers of phospholipids(bilayer).
                  • orientation causes hydrophobic centre
                    • therefor in water, phospholipids molecules automatically orientate themselves so fatty acid tail avoids water and phosphate heads are directed towards it
                      • this maintains cell membrane structure as there are two layers of phospholipids(bilayer).
                        • orientation causes hydrophobic centre
                          • prevents free diffusion of water and other polar molecules through membrane, acting as a barrier of free movement
                    • prevents free diffusion of water and other polar molecules through membrane, acting as a barrier of free movement
      • Role of lipids
        • High energy stores
          • 1g of lipid can yield twice as much energy than 1g of carbohydrate or protein
            • insoluble and stable, they can be readily respired to release energy, making ideal form of light energy store
              • when respired, lipids release many water molecules (camels hump)
        • Waterproof coverings
          • lipids repel and are impermeable to water
            • insects and leaves are covered in wax cuticles to prevent water loss
            • sea birds preen feathers with oil produced from glands
            • human skin glands produce sebum which prevents excessive drying of skin
        • insulating layers
          • poor conductors of heat and so a layer under the skin allows animals to keep warm in cooler climates
        • shock absorbing layers
          • highly compressible and so a layer under skin prevents organs against damage
          • additional lipid deposits often found around vital organs for an extra layer of protection

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