Lipids

• What are lipids?

  Lipids are a large, varied group of compounds that have very important roles in all organisms.
• What is the oxygen-to-carbon-and-hydrogen ratio in lipids compared to carbohydrates?

  • Lipids contain much smaller proportions of oxygen to carbon and hydrogen
  • Compared with carbohydrates
• Are lipids soluble in water?

  Lipids are insoluble in water.
• In which type of solvent are lipids soluble?

  Lipids are soluble in organic solvents, such as ethanol.
• How does the energy content of lipids compare to carbohydrates?

  Lipids contain more energy per gram compared with carbohydrates.
• Why are lipids more difficult to break down than carbohydrates?

  Lipids are more difficult to break down because they require hydrolysis, a process that is more complex than the breakdown of carbohydrates.
• What are the main groups of lipids?

  1. Triglycerides (fats and oils)
  2. Phospholipids
• What are the two components of a triglyceride?

  1. A glycerol molecule $(C_3H_8O_3)$

  ii. Three fatty acid chains
• What does 'R' represent in the general formula for fatty acids, $RCOOH?$


  $R$ refers to the carbon part of the fatty acid chain.
• What functional group is present at one end of fatty acid chains?

  Carboxylic acid group $(COOH)$
• What bonds are formed during the formation of a triglyceride?

  Ester bonds are formed by condensation reactions, with the release of three water molecules.
• Why are triglycerides not considered polymers?

  Triglycerides are not polymers as they are not made up from repeating monomers.
• What elements make up lipids?

  Lipids are made up of carbon, hydrogen, and oxygen.
• What causes the difference between fats and oils?

  The difference between fats and oils is due to variations in the fatty acids.
• What part of the fatty acid chain remains the same for all different fatty acids?

  $COOH,$ which is the carboxylic acid group.
• What are the two types of fatty acid chains?

  1. Saturated fatty acids
  2. Unsaturated fatty acids
• What characteristic defines saturated fatty acids?

  They have no double bonds between any of the carbon atoms along the chain and all carbon atoms are joined with hydrogen atoms.
• How are carbon atoms in saturated fatty acids joined to hydrogen atoms?

  All carbon atoms are joined with hydrogen atoms.
• How many double bonds are present in saturated fatty acids?

  Saturated fatty acids have no double bonds.
• What is a characteristic of saturated fatty acids' melting point compared to unsaturated fatty acids?

  Saturated fatty acids have higher melting points than unsaturated fatty acids.
• What state are saturated fatty acids at room temperature?

  Saturated fatty acids are solid at room temperature.
• Where are saturated fatty acids found?

  Saturated fatty acids are found in animal fats.
• What defines unsaturated fatty acids?

  They have some double bonds between carbon atoms along the chain.
• What is a monounsaturated fatty acid?

  A fatty acid with one double bond between carbon atoms.
• What is a polyunsaturated fatty acid?

  A fatty acid with more than one double bond between carbon atoms.
• Compared to saturated fatty acids, what is true about unsaturated fatty acids' melting point?

  Unsaturated fatty acids have lower melting points than saturated fatty acids.
• What state are unsaturated fatty acids at room temperature?

  Unsaturated fatty acids are liquid at room temperature.
• Where are unsaturated fatty acids found?

  Unsaturated fatty acids are found in plant oils.
• What is the second main group of lipids mentioned?

  Phospholipids.
• How does a phospholipid differ from a triglyceride?

  • One fatty acid chain is replaced by a phosphate group.
  • Phospholipids have two parts:
  • Hydrophilic head (phosphate-containing)
  • Hydrophobic tail (fatty acid tail)
• What part of a phospholipid is attracted to water?

  The hydrophilic head region.
• What part of a phospholipid repels water?

  The hydrophobic tail region.
• What important membrane structure do phospholipids form?

  They form the bilayer arrangement of the plasma membrane.
• What arrangement do phospholipids form in water?

  A double layer (bilayer).
• What types of substances can pass across the membrane facilitated by phospholipids?

  Lipid-soluble substances.
• What are the main functions of lipids?

  • Energy storage
  • Thermal insulation
  • Waterproofing
  • Buoyancy
  • Cell membrane structure
• How do lipids contribute to energy storage in living organisms?

  Lipids are excellent energy stores because they are insoluble and do not move easily out of cells. They are commonly found in animals and plant seeds.
• How do lipids provide thermal insulation?

  Fats are slow conductors of heat, helping retain body heat in animals.
• How do lipids contribute to waterproofing in organisms?

  The hydrophobic fatty acids repel water, preventing water loss. Examples include the waxy cuticle on plants and insects.
• What property of lipids contributes to buoyancy in aquatic animals?

  Lipids are less dense than water.