Lipids

• What are the main elements that lipids contain?

  Carbon, hydrogen, and oxygen
• How does the proportion of oxygen in lipids compare to carbohydrates?

  The proportion of oxygen to carbon and hydrogen is smaller in lipids than in carbohydrates
• Why are lipids considered insoluble in water?

  Because they are non-polar molecules
• In which type of solvents are lipids soluble?

  Organic solvents such as alcohols and acetone
• What are the main groups of lipids?

  • Triglycerides (fats and oils)
  • Phospholipids
  • Waxes
  • Steroids
  • Cholesterol
• What is one of the primary uses of lipids in the body?

  As an energy source for respiration
• How do lipids provide thermal insulation?

  Through structures like blubber in polar animals
• What role do lipids play in nerve cells?

  They provide electrical insulation around the axon of neurons
• What is the structure of a triglyceride molecule?

  It consists of a glycerol molecule and three fatty acid chains
• How are fatty acids joined to the glycerol molecule in triglycerides?

  By ester bonds formed through condensation reactions
• How many water molecules are eliminated when a triglyceride is formed?

  Three water molecules
• What are the characteristics of saturated fatty acids?

  They have no carbon-carbon double bonds
• What is the structure of glycerol?

  It is a 3-carbon molecule with 3 –OH groups
• Why are triglycerides considered hydrophobic?

  Because they are non-polar molecules
• How do unsaturated fatty acid chains differ from saturated fatty acids?

  Unsaturated fatty acids contain double bonds and have a “kinked” shape
• What is the significance of the bent shape of unsaturated fatty acids in membranes?

  It allows looser packing, making the membrane more fluid
• What are the components of a phospholipid molecule?

  A glycerol molecule, a phosphate group, and two fatty acid chains

  
• How are the fatty acids joined to the glycerol molecule in phospholipids?

  By ester bonds formed through condensation reactions
• What is the nature of the phosphate group in phospholipids?

  The phosphate group is polar and hydrophilic
• What is the nature of the fatty acid tails in phospholipids?

  The fatty acid tails are non-polar and hydrophobic
• What leads to the formation of bilayers in membranes?

  The non-mixing of hydrophobic tails with water
• What is the structure of cholesterol?

  It is formed of four carbon-based rings

  
• What are the two main functions of cholesterol?

  It forms the basis of steroid hormones and regulates membrane fluidity
• How does cholesterol regulate fluidity in membranes?

  By sitting between phospholipid molecules
• What are the problems associated with high cholesterol levels?

  They can lead to atherosclerosis
• How are phospholipids suited to their role in membranes?

  They are part hydrophobic and part hydrophilic, forming bilayers and controlling substance entry and exit
• How is cholesterol suited for its functions in membranes?

  It is a small, narrow molecule that slots easily between phospholipid fatty acid tails
• What are the roles of lipids in biological systems?

  • Energy source and store
  • Thermal insulation
  • Electrical insulation
  • Components of biological membranes
  • Hormonal functions
  • Waterproofing
  • Protection of vital organs