they contain carbon, hydrogen and oxygen, they are insoluble in water, they are soluble in organic solvents such as alcohols and acetone
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what are the main group of lipids called
triglycerides and phospholipids
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What are one of the roles of lipids
Cell membrane
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how do phospholipids contribute to a cell
it contributes to the flexibility of the cell membranes and the transfer of lipid soluble substances across them
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describe 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
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Describe the role of lipids in waterproofing
Lipids are insoluble in water and therefore useful as waterproofing, both plants and insects have waxy lipid cuticles that conserve water while mammals produce an oily secretion from the sebaceous gland in the skin
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Describe the role of lipids as insulators
fats are slow conductors of heat and when stored beneth the body surface help to retain body heat. They also act as electrical insulators in the myelin sheath around nerve cells
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Describe the role of lipids as protectors
fat is often stored around delicate organs such as the kidney
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why are triglycerides called 'tri'
because they have three fatty acids combined with glycerol, each fatty acid forms an ester bond with glycerol in a condensation reaction
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what would the hydrolysis of triglyceride produce
glycerol and 3 fatty acids
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what is a saturated fatty acid
a fatty acid with no carbon-carbon double bond, the carbons are combined to the maximum amount of hydrogen molecules making them saturated with hydrogen molecules
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what is mono-unsaturated
if a fatty acid has one carbon-carbon double bond
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what is polyunsaturated
if a fatty acid has more than one carbon-carbon double bond
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Why are triglycerides a great source of energy
they have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms and are therefore an excellent source of energy
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Why are triglycerides good storage molecules
they have a low mass to energy ratio so alot of energy can be stored in a small volume
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Why is this beneficial to animals
because it reduces the mass they have to carry around
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why doesnt their storage affect osmosis in cells or their water potential of them
because they are large, non-polar and insoluble in water
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Why are triglycerides important sources of water to organisms in dry deserts
because they have a high ratio of hydrogen to oxygen atoms triglycerides release water when oxidised
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how are phospholipids different from triglyceride molecules
one of the fatty acid molecules are replaced with a phosphate group, fatty acids repel watter whereas the phosphate molecule attracts water
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How would you describe the head of a phospholipid
I would describe it as hydrophilic which interacts with water but not with fat
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How would you describe the tail of a phospholipid
I would describe it as hydrophobic which mixes readily with the fat but not with the water as it is oreintated away from it
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What are molecules called that have two ends and behave in this way
polar
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Considering phospholipids are polar how will they behave in an aqueous enviornment
the phospholipid molecule will form a bilayer within the cell surface membrane which forms a hydrophobic barrier
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How does the phospholipid molecule help the cell surface membrane
The hydrophilic phosphate head helps to hold at the surface of the cell-surface membrane
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