Lipids Flashcards
State the four different types of lipids
Triglycerides, phospholipids, steroids, waxes
Describe how triglycerides can be formed and hydrolysed
Triglycerides are made up of a glycerol molecule and three fatty acid tails. An ester linkage is formed between the OH group of glycerol and carboxyl group of a fatty acid chain via condensation reaction
Compare saturated and unsaturated fatty acids
Unsaturated fatty acids have a C=C bond that creates a kink. (Cis. Trans config has no kinks)
Explain why some triglycerides exist as fats while others exist as oil at room temperature
Fats are made of saturated fatty acids which do not have kinks and pack together closely
Oils made of unsaturated fatty acids which have kinks and prevent close packing, down mpt
Explain why triglycerides are useful as energy storage molecules
Triglycerides have a high proportion of carbon and hydrogen to oxygen for an equivalent mass
Of carbohydrates. Twice as much energy (ATP) released per gram during oxidation, compact
energy store.
Hydrophobic and insoluble, will not affect water potential when stored in large amts.
Releases metabolic water upon oxidation, which is vital for survival for desert animals
Relate the structure of triglycerides to their properties and functions
Protect internal organs by providing cushioning effect
Improves buoyancy since fat is less dense than water
Thermal insulation by subcutaneous fat
State the components of phospholipids
One glycerol molecule, one phosphate head and two fatty acids
Describe how phospholipids are formed
OH groups form ester linkages with carboxyl groups of fatty acid tails by condensation.
Other OH group forms phospho-ester linkage with OH of phosphate group by condensation.
Explain phospholipids’ arrangement in aqueous medium
Amphipathic phospholipids, when in aqueous medium, arrange themselves into micelles or bilayers, where the hydrophilic heads are exposed to exterior aqueous medium while the hydrophobic tails point inwards and form a hydrophobic core.
Explain how phospholipids serve their function in biological membranes and liposomes
Phospholipids are a major component of membranes of cells and organelles. In the form of a
Phospholipid bilayer, they act as a boundary between the intracellular and extracellular env. The
Hydrophobic core prevents polar and charged particles from passing through due to hydration
Shells. It is thus partially permeable. Phospholipids are able to move laterally in the bilayer
Which ensures fluidity of the membrane and creates transient pores. Also liposomes.
Describe the structure and properties of steroids, using cholesterol as an example.
Four fused ring structure. Insoluble in water, soluble in organic solvents. Cholesterol has a
Hydrophilic OH group and hydrophobic ring structure. So slightly amphipathic.
Explain how cholesterol is important to membranes.
Cholesterol regulates membrane fluidity.
At low temperatures, cholesterol prevents close-packing of phospholipids which prevents them
From freezing.
At high temperatures, cholesterol restricts phospholipid movement to prevent the membrane
From being overly fluid.
State the name of the test for lipids. Describe the steps for the test for the presence of lipids.
Ethanol Emulsion Test
Add 2cm3 ethanol to 2cm3 test solution and shake well. Allow it to stand for 2min.
Decant into another test tube of 2cm3 water and Observe for white emulsion. If solution remains clear, then lipids are absent.
