lipids

• triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acids
• glycerol is an alcohol with three hydroxyl groups
• a condensations reaction between glycerol and a fatty acid (R-COOH) forms an ester bond
• The R-Group of a fatty acid may be saturated or unsaturated
• in phospholipids one of the fatty acids of a triglyceride is substituted by a phosphate containing group
• triglycerides:

  • plant oils and animal fats
  • non polar
  • hydrophobic
  • don’t dissolve in water
  • one glycerol with three fatty acuds
• lipids: carbon hydrogen ocygen
• lipids aren’t polymers because the three fatty acids aren’t repeated monomer units
• lipids are joined by ESTER bonds
• structure of triglycerides

  • glycerol molecule always the same
  • different properties come from variations in fatty acids
  • all fatty acids have a carboxyl group (-COOH) with a hydrocarbon chain attached (R-group)
• Saturated: every carbon atom joined by a single bond in the hydrocarbon tail of fatty acid
• Unsaturated:

  • if one or more carbon in the hydrocarbon tail of the fatty acid is a double bond
• unsaturated is oil at room temperature
• triglycerides with unsaturated fatty acid tails are not able to be tightly packed and this is Oils , liquid at room temp
• triglycerides with fully saturated fatty acid tails can pack tightly against one another because the single bonds result in straight molecules, this generates fats and waxes that are solid at room temp (butter)
• relating the structure of triglycerides to function:

  • mainly used as energy store molecules found as droplets
  • have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms and are therefore an excellent source of chemical energy when broken down
• relating triglycerides structure to their function:

  • have a low mass to energy ratio making them good storage molecules as lots of energy can be stored in a small volume and the mass of an organism isn’t increased so doesn’t hinder movement
• relating triglycerides structure to their function:

  • are large non-polar molecules and therefore insoluble in water so storing them does not have an osmotic effect on cells
• relating triglycerides structure to their function:

  • have a high ratio of O atoms to H atoms and are a metabolic source of water so water can release when they are oxidised providing an important source of water especially to organisms in dry climates
• triglycerides formed by condensation reaction, the byproduct is 3 waters
• Phospholipids made up of two sections or poles

  known as polar molecules
• Phospholipids have

  • hydrophobic tail so, the fatty acid molecules repel water, the tail orientates itself away from water but readily mixes with fat
  • hydrophilic head, phosphate molecules attract water, but not fat
• phospholipids combine with carbohydrates to form glycolipids involved in cell recognition
• Phospholipids in cell membranes

  • water soluble molecules cant pass through easily because of the phospholipids barrier
• test for lipids:

  • add ethanol to the sample
  • shake one minute
  • add water
  • a white emulsion forms
• What is the scientific name for molecules found in fats and oils?

  Lipids
• What are the functions of lipids?

  • Major source of energy in the diet
  • Energy storage (e.g., adipose tissue)
  • Insulation to reduce heat loss
  • Protection of internal organs
  • Waterproofing (e.g., oils on feathers)
  • Structural component of membranes
• What are two examples of where lipids can be found?

  Oils such as olive oil and solid fats such as butter
• What role do lipids play in waterproofing?

  They coat feathers of aquatic birds to prevent water absorption
• What are the two main categories of lipids?

  Triglycerides and phospholipids
• What is the general structure of a triglyceride?

  One molecule of glycerol bonded to three fatty acid molecules
• What are the two key parts of a fatty acid molecule?

  A carboxylic group and a long chain of carbon atoms
• What characterizes a saturated fatty acid?

  It contains only single covalent bonds between carbon atoms
• What distinguishes a monounsaturated fatty acid from a polyunsaturated fatty acid?

  A monounsaturated fatty acid has one double bond, while a polyunsaturated has two or more
• What is the process of forming triglycerides called?

  • Formation involves one glycerol and three fatty acids
  • The reaction creates an ester bond
  • This process is called esterification
  • A molecule of water is produced (condensation reaction)
• What type of reaction occurs when triglycerides are formed?

  Condensation reaction
• What happens to triglycerides in the digestive system?

  They are broken down by lipase enzymes
• What is required for the hydrolysis of triglycerides?

  Three water molecules
• Why are triglycerides considered hydrophobic?

  They are non-polar molecules and do not dissolve in water
• What is the significance of the large number of carbon and hydrogen atoms in triglycerides?

  They allow for a great deal of energy to be released