Lipids

• Ester bond


  A type of bond formed by a condensation reaction which joins each of the fatty acid tails to the glycerol molecule in a triglyceride
• Saturated fatty acid


  A type of fatty acid molecule containing only single bonds between the carbon atoms
• Triglyceride


  A type of lipid formed from a molecule of glycerol joined by ester bonds to three fatty acid molecules
• High-density lipoproteins (HDL)


  A dense molecule made of proteins and lipids that is used to remove cholesterol from tissues and transport it to the liver for excretion
• Unsaturated fatty acid


  A type of fatty acid molecule containing at least one double bond in the carbon chain
• Low-density lipoproteins (LDL)


  A lower density molecule made of proteins and lipids that is used to transport cholesterol around the body to different tissues which can cause cholesterol buildup in blood vessels
• Intermolecular forces

  Weaker in unsaturated lipids, leading to a lower melting point
• Lipids


  • Saturated lipids (found in animal fats, no carbon-carbon double bonds)
  • Unsaturated lipids (found in plants, contain carbon-carbon double bonds and melt at lower temperatures than saturated fats)
• Plant oils

  • Often unsaturated
• Unsaturated lipids

  • Weaker intermolecular forces due to double bonds creating a 'kink' in the hydrocarbon chain
  • Solid at liquid temperature for saturated fats and liquid at room temperature for unsaturated lipids
• High density lipoprotein transports cholesterol from body tissues to the liver for breakdown, reducing cholesterol levels and the risk of atherosclerosis
• Triglycerides

  1. One molecule of glycerol and three fatty acids joined by ester bonds formed in condensation reactions

  2. Used as energy reserves in plant and animal cells
• High and Low Density Lipoproteins

  • High density lipoprotein ('good' cholesterol)
  • Low density lipoprotein ('bad' cholesterol)
• Lipids


  • Waterproof due to the hydrophobic fatty tail
  • Very compact and provide better gram-for-gram energy release than carbohydrates or proteins
  • Non-polar and insoluble in water, good for storage and don't interfere with water-based reactions in the cytoplasm
  • Conduct heat slowly providing thermal insulation
• Unsaturated lipids


  • Contain carbon-carbon double bonds
  • Melt at lower temperatures than saturated fats
• Animal fats

  • Normally saturated
• Phospholipids


  1. One of the fatty acids of a triglyceride is substituted by a phosphate-containing group

  2. Phosphate heads are hydrophilic and tails are hydrophobic, forming a bilayer in the cell membrane
• Cholesterol is a soluble lipid made in the body and transported by proteins in soluble complexes called lipoproteins consisting of proteins and lipids
• Low density lipoprotein transports cholesterol from the liver to the blood, causing cholesterol levels to increase and is linked to atherosclerosis
• HDL

  Proportion of protein is higher, whereas the proportion of cholesterol & fat is lower
• Link between cholesterol and cardiovascular diseases

  Causal because cholesterol is involved in plaque formation
• LDL (‘bad’ cholesterol)


  Formed from saturated fats, protein, and cholesterol; transports cholesterol from the liver to the blood, causing an increase in cholesterol levels, linked to atherosclerosis
• Correlation between high levels of saturated fats and high blood cholesterol

  Saturated fats are components of low-density lipoproteins