LIPIDS

• What are lipids?


  Large complex molecules called macromolecules that are non polar, as electrons in outer orbitals that form bonds are more evenly distributed; making them insoluble in water.
• What is a triglyceride?

  A type of fat molecule, consisting of one glycerol backbone (the central framework) and three fatty acids. The length and saturation of these fatty acids influence whether the triglyceride is solid or liquid at room temperature.
• What is glycerol or glycerine?

  A type of sugar alcohol, consisting of three carbon atoms, each attached to hydroxyl group (OH). This makes it a trihydroxy alcohol, a type of alcohol containg three hydroxyl groups.
• What bonds are present between the fatty acids and glycerol?

  Ester bonds, formed through esterification, a condensation reaction.
• How are triglycerides broken down?

  Through hydrolysis, requiring three water molecules, due to three ester bonds being present.
• What is a fatty acid?

  A long chain of carbon and hydrogen atoms with a carboxyl group (-COOH) at one end.
• What is the role of triglycerides?

  1. Thermal insulation to reduce heat loss, as stored in fat tissues.
  2. Protection of vital organs, as stored in fat tissues.
  3. Energy storage, triglycerides the most concentrated form of energy storage, and when energy is needed they are broken down via lipolysis, to release glycerol and three fatty acids; which can be used to generate ATP.
  4. Metabolic role, they are involved in energy production during periods of fasting or increased energy demand.
• What are the first five roles of lipids?

  1. Thermal and electrical insulation, maintaining body temperature, and allowing impulse transmission.
  2. Protection, adipose tissue, which stores triglycerides, cushion organs from mechanical shock.
  3. Signalling molecule production, such as steroid hormones derived from cholesterol, and eicosanoids derived from fatty acids.
  4. Cell signalling, eg. glycolipids on cell surface help in cell interaction and immune response.
  5. Storage of vitamins, some vitamins (eg. A, D, E and K) are soluble in fats, so are transported by them in blood plasma by lipoproteins.
• What are the other five roles of lipids?

  1. Membrane formation, phospholipids and cholesterol provide structure and fluidity.
  2. Hydrophobic barrier formation, phospholipids form a bilayer that allows for selective permeability.
  3. Energy store and transport, efficient for long term storage and transport of lipid-soluble material, via lipoproteins.
  4. Water proofing for feathers ect, due to hydrophobic barrier.
  5. Buoyancy for aquatic species, due to storage in fat tissues.
• What does saturated mean?

  Fatty acid chains with no double bonds between carbon atoms in its hydrocarbon chain, as all carbon atoms have formed the maximum number of bonds with hydrogen atoms. Saturated fatty acids chains could lead to coronary heart disease.
• What does unsaturated mean?

  Fatty acids with one or more double carbon bonds in their hydrocarbon chain, if there is one double bond it is monosaturated, and if there is more than one it is polysaturated. The double bonds cause the chain to kink and bend, preventing the molecules form packing together tightly, and making them liquid at room temperature; oils instead of fats.
• How do we test for lipids?

  Sudan III test or emulsion test.
• What is an emulsion test?

  This involves mixing the sample with ethanol, before mixing the solution with water and shaking well. If a white emulsion forms as a layer, this is a positive results, and shows the presence of lipids.
• What is a Sudan ||| test?

  Involves adding equal parts water to your sample, before adding drops of Sudan ||| and shaking well. A red stained layer may form on the surface, indicating the presence of lipids.
• What are sterols (steroid alcohols)?

  A type of lipid, complex alcohol molecules consisting of a four carbon ring structure with a hydroxyl group at one end. The hydroxyl group is polar and hydrophilic, while the rest of the molecule is hydrophobic, eg. cholesterol made in the liver and intestines.
• How do sterols help membrane formation?

  Sterols are positioned between phospholipids with hydroxyl groups on the outer border of the membrane, the periphery. This helps with stability and fluidity regulation by making the membrane fluid at low temperatures, and preventing too much fluidity at high temperatures.
• What are phospholipids?

  Phospholipids are a type of lipid molecule that make up the basic structure of cell membranes, consisting of phosphorus, carbon, oxygen, and hydrogen; with one fatty acid chain in triglycerides replaced with a phosphate group to form a phospholipid. Phosphate groups have extra electrons, making them negatively charged and soluble in water.
• What is the structure of phospholipids?

  They have a dual hydro nature they have a non polar tail (fatty acid tail) and charged head (phosphate head). The non polar, hydrophobic tails are repelled by water, facing toward the sheet centre, and the hydrophilic heads are attracted, protecting the tails in a two sheet formation. This membrane separates an aqueous environment from aqueous cytosol in cells.
• What are surfactants or surface active agents?

  Compounds with both hydrophobic and hydrophilic segmants.