Lipids Flashcards
Describe structure and properties of amino acids Describe formation and breakage of peptide bond Explain primary, secondary, tertiary and quaternary structure Explain effects of temperature and pH Describe structure and properties of haemoglobin and collagen
Glycerol
3 carbon alcohol, each bearing hydroxyl group (OH)
Fatty acid
Long non-polar, hydrophobic hydrocarbon chains
Carboxyl group (COOH) at one end
Saturated or unsaturated
Cannot form hydrogen bonds with water
Triglyceride molecule
3 fatty acid molecules + 1 glycerol molecule
Ester linkage (between OH and COOH group)
Condensation reaction
Properties of triglycerides
Non-polar -> do not form H-bonds with water molecules
Hydrophobic
Insoluble -> does not affect water potential of cells
Cis-double bond (unsaturated fatty acid chains) -> kinks -> pack less closely
Functions of triglycerides
Compact energy storage
Higher proportion of carbon and hydrogen atoms and lower proportion of oxygen -> higher proportion of C-H bonds -> more reduced -> release more energy during oxidation
Produces metabolic water
Other functions of triglycerides
Protect internal organs
Thermal insulation
Improve buoyancy
Storage of fat soluble vitamins like A, D and K
Phospholipids
2 fatty acid molecules + 1 glycerol molecule + 1 phosphate group (negative electrical charge)
Phosphoester linkage
Properties of phospholipids
Amphipathic -> both hydrophilic (negatively-charged phosphate head) and hydrophobic (non-polar hydrophobic hydrocarbon tails) regions
Functions of phospholipids
Membranes -> phospholipid bilayer -> boundary
Hydrophobic core only permeable to small hydrophobic solutes and low permeability to polar and charged molecules/ions -> barrier -> partially permeable
Can move laterally -> fluid
Form vesicles
Properties of steroids
Slightly amphipathic -> hydrophobic hydroxyl group and hydrophobic ring structure
OH group aligns with phosphate heads of phospholipids (H-bonds)
Remaining portion tucked into hydrophobic core (Van der Waals forces)
Functions of steroids
Cholesterol regulates membrane fluidity -> stabilises membrane
At high temperatures -> restrict phospholipid movement through its interactions -> prevented from being overly fluid
At low temperatures -> prevents close packing of phospholipids -> prevents solidification/from being overly firm
Fat test
Ethanol emulsion test 2cm3 of ethanol 2 drops of test sample Mix well and allow it to stand for 2 min Decant ethanol into another test tube containing 2cm3 water White emulsion if lipids present
