Lipids

• What are the most common types of lipids?

  Triglycerides
• What elements do lipids contain?

  Carbon, hydrogen, and oxygen atoms
• Why are triglycerides insoluble in water?

  Because they are non-polar
• What solvents can triglycerides dissolve in?


  Ethanol, chloroform, and ether
• How are triglycerides formed?

  By a condensation reaction between glycerol and fatty acids
• What is released during the formation of triglycerides?

  Three molecules of water
• What type of bond is formed in triglycerides?

  An ester bond
• How can an ester bond be broken?

  By hydrolysis
• How many ester bonds does a triglyceride have?

  Three ester bonds
• What characterizes unsaturated fatty acids?

  They have double bonds between neighboring carbon atoms
• What effect do double bonds have on fatty acids and lipids?

  They make them melt more easily
• What is a monounsaturated fatty acid?

  A fatty acid with only one double bond
• What is a polyunsaturated fatty acid?

  A fatty acid with two or more double bonds
• Why do unsaturated fatty acids have a kink in their structure?

  Because of the presence of a double bond
• What characterizes saturated fatty acids?

  They have no double bonds between neighboring carbon atoms
• What is the state of saturated fatty acids at room temperature?

  They are solid
• What is the link between saturated fatty acids and heart disease?

  High consumption of saturated fatty acids is linked to heart disease
• What are the main causes of heart disease?

  Atherosclerosis and hypertension
• What happens when a diet is high in saturated fats?

  Low-density lipoproteins (LDL) build up
• What is atheroma?

  Fatty material deposited in the coronary arteries
• What can result from restricted blood flow due to atheroma?

  Angina or myocardial infarction
• What is the role of high-density lipoproteins (HDL)?

  They carry harmful fats to the liver for disposal
• What is the relationship between HDL and LDL in terms of heart disease risk?

  A higher ratio of HDL:LDL lowers the risk of heart disease
• What is the structure of phospholipids?

  They have a phosphate group and two fatty acid tails
• Why are phospholipids important in water?

  They form micelles with hydrophobic tails inward
• What forms when enough phospholipid molecules are present in water?

  A bilayer is formed
• What do the hydrophilic heads and hydrophobic tails of phospholipids do in a bilayer?

  Hydrophilic heads point outward, tails point inward
• What are the key differences between triglycerides and phospholipids?

  • Triglycerides: 3 fatty acid tails, no phosphate group, non-polar
  • Phospholipids: 2 fatty acid tails, phosphate group, polar head (hydrophilic)
• What indicates the presence of lipids in a sample during the test?

  The formation of a cloudy white emulsion
• How can you test for the presence of fats and oils?

  By mixing with absolute ethanol and adding water
• What are the functions of triglycerides in organisms?

  • Energy reserve (more energy than carbohydrates)
  • Thermal insulator (reduces heat loss)
  • Protection (around delicate organs)
  • Metabolic water source (produces water when oxidized)
  • Waterproofing (reduces water loss)
  • Low density and buoyancy (helps float)
  • Nerve transmission (forms myelin sheath)
• What are the functions of phospholipids?

  • Form the bilayer of cell membranes
  • Allow transport of non-polar molecules by simple diffusion
• What are the functions of steroids and cholesterol?

  • Steroids include sex hormones (testosterone and oestrogen)
  • Have a ring structure rather than a long chain structure