Biological molecules: Lipids Flashcards
What characteristics do all lipids share?
- They all contain carbon and oxygen
- the proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
- they are non polar due to the large % of carbons and hydrogens making them hydrophobic
- they are soluble in organic solvents like alcohols and acetones
What are the main groups of lipids?
Triglycerides (fats and oils) and phospholipids
What are the roles of lipids and explain each one
- phospholipids contribute to the flexibility of cell membranes and the transfer of lipids soluble substances across them
- they’re a source of energy as when oxidised, lipids provide over twice the energy as the same mass of carbohydrate and release valuable water
- they are useful for waterproofing as they are hydrophilic. Plants have a waxy lipid cuticle that conserves water and mammals produce an oily secretion from the sebaceous glands in the skin
- provide insulation as fats are slow conductors of heat and when stored beneath the body surface help to retain body heat and act as an insulator in the myelin sheath around nerve cells
- provide protection as fat is stored around delicate organs like the kidneys and the heart
What’s the difference between fats and oils?
Fats are solid at room temp but oils are liquid
What are triglycerides made up of?
3 fatty acids bonded to glycerol
How is a triglyceride formed?
Through the condensation reaction of three fatty acids and a glycerol
In a triglyceride what is the bond called between each fatty acid and OH group from the glycerol?
An Ester bond
What is the structure of a glycol and fatty acid molecule?
(Check biology camera album)
What does the fact that the glycerol molecule in a triglyceride is the same mean about the difference in properties of fats and oils?
The differences in the properties of different fats and oils come from the variation of fatty acids
How many different fatty acids are there and what do they all have?
70 different fatty acids and they all have a carboxyl (-COOH) group with a hydrocarbon chain attached.
When is a fatty acid saturated?
If the hydrocarbon chain has no carbon - carbon double bonds as all the carbon atoms are linked to he maximum possible number of hydrogen atoms.
When is a fatty acid mono-unsaturated?
If here is one double bond present in the hydrocarbon chain
When is a fatty acid polyunsaturated?
If there is 2 or more double bonds in the hydrocarbon chain
What are the four ways the structure of triglycerides relate to their properties?
- they have a high ratio of energy storing carbon - hydrogen bonds to carbon atoms making them an excellent source of energy
- have a low mass - energy ratio making them good storage molecules as much energy can be stored in a small storage volume so benefits animals as it reduces the mass they have to carry to move around
- they are insoluble in water as they are large non - polar molecules and so doesn’t affect osmosis in cells or the water potential of them
- As they have a high ratio of hydrogen to oxygen atoms, they release water when oxidised and so provide an important source of water especially for organisms living in dry deserts
What are the properties of saturated fatty acids?
- have no double bonds
- form linear hydrocarbon chains
- solid at room temp
- high melting points
- pack closely together