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lipids Flashcards

1
Q

what is the elemental composition of lipids

A

oxygen, hydrogen, carbon

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2
Q

what is the structure of saturated fatty acids

A

-each carbon atom is fully saturated with its full quota of hydrogen atoms

-no double bonds occur between the carbon atoms

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3
Q

what is the consistency and melting point of saturated fatty acids

A

-solid at room temperature (18C)

-high melting point

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4
Q

what are the sources of saturated fatty acids and give examples

A

-generally found in animal sources
-e.g. butyric acid in butter and stearic acid in meat

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5
Q

what is the structure of monounsaturated fatty acids

A

-each carbon is not fully saturated with a full quota of hydrogen atoms

-there is one double bond between the carbon atoms

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6
Q

what is the consistency and melting point of monounsaturated fatty acids

A

-soft or liquid at room temperature (18C)

-low melting point

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7
Q

what are the sources of monounsaturated fatty acids and give examples

A

-generally found in plant and marine sources

-e.g. oleic acid in olive oil

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8
Q

what is the structure of polyunsaturated fatty acids

A

-each carbon atom is not fully saturated with a full quota of hydrogen atoms

-there is more than one double bond between the carbon atoms

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9
Q

what is the consistency and melting point of polyunsaturated fatty acids

A

-soft or liquid at room temperature (18C)

-lowest melting point of all the fatty acids

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10
Q

what are the sources of polyunsaturated fatty acids and give examples

A

-generally found in plant and marine sources

-e.g. linoleic acid in nuts and linolenic acid in seeds

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11
Q

what are essential fatty acids

A

essential fatty acids are acids that cannot be manufactured by the body and therefore must be obtained from food

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12
Q

what are the sources of essential fatty acids

A

-nuts

-seeds

-olive oil

-oily fish

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13
Q

what are the biological functions of essential fatty acids

A

-aid cell membrane formation, which is essential for growth

-reduce the risk of coronary heart disease by raising high-density lipoprotein which helps remove cholesterol from the blood and by lowering low-density lipoprotein which deposits cholesterol in the blood

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14
Q

describe the structure of an omega-3 fatty acids

A

omega-3 fatty acids have a double bond between the third and fourth carbon atoms along their hydrogen chain

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15
Q

what are the sources of omega-3 fatty acids

A

-oily fish

-seeds

-nuts

-fish oils

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16
Q

what are the biological functions of omega-3 fatty acids

A

-reduce the risk of coronary heart disease, heart attacks and strokes by raising HDL and lowering LDL

-decrease the viscosity of blood, preventing clots or blockages in the coronary arteries

-aid foetal brain development during pregnancy as well as helping to improve memory and cognitive functioning throughout life

17
Q

what is the chemical structure of cis fatty aids

A

the hydrogen atoms on either side of the double bond are both above or both below the carbon chain

18
Q

what are the sources of cis fatty acids

A

naturally occurring in foods such as olive oil and oily fish

19
Q

what is the significance of cis fatty acids in the diet

A

generally good for health as they raise HDL while lowering LDL decreasing the risk of coronary heart disease

20
Q

what is the structure of trans fatty acids

A

the hydrogen atoms on either side of the double bond are on opposite sides of the carbon chain

21
Q

what are the sources of trans fatty acids

A

-the heating or frying of oils at high temperatures
-pastries and crisps

22
Q

what is the significance of trans fatty acids in the diet

A

generally bad for health as they lower HDL while raising LDL increasing the risk of coronary heart disease

23
Q

what are the properties of lipids

A

-solubility
-absorption of flavours
-emulsions
-hydrogenation
-rancidity
-plasticity

24
Q

explain solubility as a property of lipid

A

lipids are insoluble in water. they are soluble in solvents such as ether and benzene

25
Q

explain absorption of flavours as a property of lipid

A

lipids absorb flavours easily, e.g. chilli oil

26
Q

explain heating lipids as a property of lipid

A

melting point: solid fats melt when heated to 30-40C

smoke point: if lipids are heated to 200C or 250C they begin to decompose causing the glycerol to separate from the fatty acids. glycerol is then broken down into acrolein and produces a blue smoke or haze and a harsh smell

-flash point: extreme overheating of lipids to 310C and 325C causes vapour to be released that can spontaneously catch on fire

27
Q

explain emulsion as a property of lipid

A

an emulsion is a colloidal solution, formed when two immiscible liquids are forced to mix together. emulsion can be described as water in oil emulsions or oil in water emulsion

28
Q

what is water in oil emulsion

A

e.g. butter, margarine. tiny droplets of water are dispersed throughout oil or fat

29
Q

what is oil in water emulsion

A

e.g. milk, mayonnaise. tiny droplets of oil are dispersed throughout the water

30
Q

what is temporary emulsion

A

formed when the two immiscible liquids, e.g. vinegar and oil are in vinaigrette, are shaken vigorously. if left to stand they will seperate

31
Q

what is permanent emulsion

A

formed when an emulsifier is added to two immiscible liquids, preventing them from separating, e.g. vinegar and oil in mayonnaise

32
Q

what is emuslifiers

A

are molecules that have a hydrophilic (water-loving) head and a hydrophobic (water-hating) tail. when an emulsifier is added to a mixture of two immiscible liquids the hydrophilic head attaches itself to the water and the hydrophobic tail attaches itself to the oil. this prevents the liquids from separating, creating a permanent emulsion

33
Q

what is a stabilisers

A

are long-chained molecules that helps to maintain emulsions by separating the oil droplets and preventing them from coalescing

34
Q

explain hydrogenation as a property of lipid

A

is a process whereby hydrogen gas, in the presence of a nickel catalyst is forced through the double bond of an unsaturated oil, converting the unsaturated oil into a saturated solid fat, e.g. used in the production of margarine

35
Q

explain rancidity as a property of lipid

A

is the spoilage or decomposition. this results in an unpleasant odour and taste. there are two types of rancidity: oxidative and hydrolytic rancidity

36
Q

what is oxidative rancidity

A

occurs when oxygen in the air combines with the carbons in a double bond of the unsaturated fatty acid

37
Q

what is hydrolytic rancidity

A

occurs when enzymes or bacteria break down lipids into glycerol and fatty acids

38
Q

explain plasticity as a property of lipid

A

describes how soft, flexible and shapable a fat is at a given temperature. it is determined by the degree of saturation, the more saturated fatty acids present, the more solid the lipid

39
Q

what is the biological functions of lipids

A

-lipids supply the body with heat and energy, helping to keep the body temperature at 37C and providing energy for all activities

-lipids form a protective layer that surrounds delicate organs, e.g. the kidneys

-lipids supply the body with the fat-soluble vitamins A,D,E and K which are necessary for overall health

-excess lipid intake is stored as adipose tissue under the skin. this insulates the body and acts as an energy reserve

home economics (35 decks)

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