Lipids Flashcards
What characteristics do all lipids share?
They all contain hydrogen, carbon and oxygen. The proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates. Insoluble in water, soluble I alcohol, acetone, and in organic solvents.
What are the to main groups of lipids?
triglycerides (fats and oils) and phospholipids.
How do phospholipids contribute to membranes?
They add flexibility and the transfer of lipid-soluble substances across them.
What is the role of lipids as a source of energy?
When oxidised, lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water.
What is the role of lipids in waterproofing?
Lipids are insoluble in water and therefore useful as a waterproofing. Both plants and insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in the skin.
What is the role of lipids in insulation?
Fats are slow conductors of heat and when stored beneath the body surface help to retain body heat. They also act as electrical insulators in the myelin sheath around nerve cells.
What is the role of lipids in protection of the body?
Fat is often stored around delicate organs, such as the kidney.
Where do triglycerides get their name?
They have three (tri) fatty acids combined with glycerol (glyceride). Each fatty acid forms an ester bond with glycerol in a condensation reaction, therefore hydrolysis of a triglyceride produces glycerol and three fatty acids.
Why do fats and oils differ in properties?
They come from different variations of fatty acids.
What do all fatty acids have in common?
They all have a carboxyl group (-COOH) with a hydrocarbon chain attached, if this chain has no carbon-carbon double bonds it is said to be saturated.
If there is a single double bond what do we call the molecule?
mono-unsaturated, if there are multiple bonds present we call it polyunsaturated.
Why are triglycerides an excellent source of energy?
They have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms.
Triglycerides have low mass to energy ratio, why is this useful?
It makes them good storage molecules because much energy can be stored in a small volume. This is beneficial to animals as it reduces the mass they have to carry around as they move.
Why does the storage of triglycerides not affect osmosis in the cells or the water potential of them?
As they as large, non-polar molecules, triglycerides are insoluble.
Define ‘water potential’.
The pressure created by water molecules . It is the measure of the extent to which the solution gives out water. The greater the number of water molecules present, the higher (less negative) the water potential.
