lipids definition
- composed of carbon, hydrogen, oxygen
- less number of oxygen compared to hydrogen
- much higher proportion of hydrogen and carbon in relation to oxygen of the same mass
- highly insoluble in water
- soluble in organic
lipids (3 types)
- simple lipids
- compound lipids
- steroids and sterols
triglyceride molecule (composition)
two compounds
- 3 fatty acids and one glycerol
- all macromolecules , not polymers
simple lipids
- formed when an alchohol (glycerol) molecule is joined with fatty acids via ester linkage
- glycerol C3H8O3
fatty acid: a hydrocarbon chain + carboxyl group
why low solubility in water
- effect of non-polar hydrocarbon chain is enough to overcome polarity of carboxyl group
- hydrocarbon chain is hydrophobic -> lipids are insoluble in water
triglyceride
- condensation of 3 fatty acid chains and glyceride (alcohol) through ester linkage
- hydroxyl group present in glycerol molecule react with carboxyl group of fatty acid molecule
- water molecule is removed and ester bond is formed between glyecerol and fatty acid molecule
esterification
ester bond formed between glycerol and fatty acid molecule when water molecule is removed
- ester linkage is formed between hydroxyl group of glycerol and carboxyl group of A fatty acid
- each glycerol molecule has three hydroxyl groups -> 3 water molecule is removed with an addition of 3 fatty acid molecules
- fatty acid present on triglyceride molecule can be the same positions (simple triglycerides), or can contain two or more different fatty acids
triglycerides properties
- give rise to fatty acids and glycerol through hydrolysis (breaking of triglycerides)
- non-polar and hydrophobic – no uneven distribution of charge within molecule + presence of long hydrophobic carbon chains in the fatty acids
+ carboxyl group was polar, but through esterification becomes non polar-> hydrophobic - insoluble in water: non polar, cannot form hydrogen bonds with water molecules
- soluble in organic solvents
- less dense than water
function of triglycerides: (6)
energy storage
metabolic water
thermal insulation
buyancy
mechanical protection
essential nutrients
function one: energy store
- stores alot of energy
- lipids have higher proportion of hydrogen and carbon per gram compared with carbohydrates
- important in long term energy store -> hibernating animals
function two: metabolic water
- metabolic water produced from oxidation of energy substrates
- important for survival desert animals who store fats for this purpose
function three: thermal insulation
- lipids reduce loss of body heat by acting as a thermal insulator below the skin of vertebrates
- good thermal insulator as they conduct heat slowly, reducing the loss of body heat from deeper regions of the body to the outside
- important to aquatic mammals and mammals living in cold climates
function four: buoyancy
- triglycerides are less dense than water
- animals that live in cold climates for example, walruses and whales have a thick layer of blubber, contributing to buoyancy
function 5: mechanical protection
- fat forms a natural buffer (packing material), that absorbs shock and helps cushion fragile internal organs (visceral fat)
function 6: essential nutrients
- fat supplies essential fatty acids (linoleic acid) for proper growth and development
- aids in the absorption of fat-soluble vitamin (A, D, E, K) from intestinal tract. excess fat-soluble vitamin are store in fat tissues so they need not be ingested daily
- vitamins are organic compounds that are required in trace amounts for normal metabolism but are not synthesised by organism that requires them
- vitamins b and c are water soluble but other fat-soluble
compound lipids
consists of lipid component and non lipid component
- amphipathic (hydrophillic and hydrophobic)
phospholipids:
1 phosphate group
+ i glycerol molecule
+ 2 fatty acid chains
polar head: phosphate
non-polar tail: hydrocarbon chains
function of phospholipid
- formation of micelles or bilayers
- compartmentalisation of organelles
- phospholipids create boundaries between the cell and its external environment.
glycolipids
carbohydrates covalently bonded to lipids to form glycolipids
- cell-cell recognition and cell-cell adhesion
steroids and steorls
