lipids Flashcards

1
Q

what are fats

A

lipids that are solid at room temp

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2
Q

what are oils

A

lipids that are liquid at room temp

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3
Q

what are lipids made up of

A

triglyceride, when one glycerol molecule joins with three fatty acids and three water molecules are eliminated

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4
Q

what is the formula for a fatty acid

A

CH3(CH2)nCOOH

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5
Q

What differentiates a fatty acid

A

number of carbon atoms

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6
Q

what are the classifications of fatty acids

A

saturated, monounsaturated and polyunsaturated

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7
Q

what is saturation in terms of a fatty acid

A

the amount of hydrogen molecules are present in a fatty acid

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8
Q

what is the structure of a saturated fatty acid

A

each carbon atom has it full quota of hydrogen, no double bonds between carbon atoms

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9
Q

what are the consistency and melting point of the three fatty acid types

A

saturated: solid at room temp and high melting point, monounsaturated: soft or liquid at room temp, low. melting point, polyunsaturated: soft or liquid at room temp, lowest melting point

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10
Q

what are sources and examples of saturated fatty acids

A

animal sources, butyric acid in butter, stearic acid in meat

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11
Q

what is the structure of monounsaturated fatty acids

A

each carbon is not fully saturated with hydrogens and there is one double bond between carbon

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12
Q

what are sources and examples of monounsaturated fatty acids

A

plant and marine sources, oleic acid in olive oil

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13
Q

what are sources and examples of polyunsaturated fatty acids

A

plant and marine sources, alpha linolenic acid in seed oil snd linolenic acid in seeds

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13
Q

what is the structure of polyunsaturated fatty acids

A

each carbon is not fully saturated with full quota of hydrogen and there is more than one double bond between carbons

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13
Q

what are essential fatty aids

A

cannot be manufactured in the body so must be obtained by food, eg alpha linolenic acid, a type of omega 3

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14
Q

what are the functions of essential fatty acids

A

aids cell membranes formations, reduces risk of CHD by raising HDL which help remove cholesterol and lower LDLs

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14
Q

what are omega 3 fatty acids

A

polyunsaturated fatty acids that have a double bond between the third and fourth carbon on the hydrocarbon chain.

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15
Q

what are the two main types of omega 3 fatty acids

A

EPAs and DHAs

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16
Q

what are sources of omega 3 fatty acids

A

oily fish and nuts

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17
Q

what are the functions of omega 3 fatty acids

A

reduced risk of CHD, heart attack, stroke by raising HDL and lowering LDLs, decreases blood viscosity which prevents blood clots, aids foetal brain development as well as improving memory and cognitive function

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18
Q

what are cis fatty acids

A

two hydrogen bonds on the same side of the double bond, they are generally good for health by increasing HDL

19
Q

what are trans fatty acids

A

two hydrogen atoms on opposite sides of the double, formed from cis fatty acids during the heating of oils at high temps and during industrial processes, generally bad for health as they raise LDL

20
Q

what are alternatives to saturated fats like butter or lard

A

fats containing trans fatty acids

21
Q

what is the function of cholesterol

A

made in the liver for cell function and hormones, excess however from saturated fatty foods builds up in the arteries

22
Q

what is artherosclerosis

A

when cholesterol clings to the artery walls and restricts blood flow to organs like the heart and brain and hardens the arteries, risks of heart attacks, angina and strokes

23
Q

what is a lipoprotein

A

occurs when cholesterol binds with proteins and either makes high density pr low density lipoproteins

24
Q

what do HDLs do

A

mop up loose cholesterol from arteries and carries it back to the liver where it is broken down

25
Q

what do LDLs do

A

deposits on the walls of arteries

26
Q

what are the properties of lipids

A

solubility, absorption of flavours, heating lipids, emulsions, emulsifiers, hydrogenation, rancidity, plasticity

27
Q

what is solubility of lipids

A

insoluble in water but soluble in solvents like benzene

28
Q

what are the three points of heating lipids

A

melting point: Solid fats melt when heated at 30-40 degrees, smoke point: If lipids are heated to 200˚C
(fats) or 250˚C (oils), the glycerol begins to separate from the 3 fatty acids and is broken down into acrolein
and produces a blue haze/smoke and an acrid smell. flash point: Extreme overheating of lipids to 310˚C (fats) and 325˚C (oils) causes the vapour to be emitted that can spontaneously burst into flames/ignite .

29
Q

what is absorption of flavours of lipids

A

lipids absorb flavours easily, culinary app: infused oils or garlic butter

30
Q

what is an emulsion of lipids

A

a collodial solution formed when two immiscible liquids are forced to mix together and suspended microscopic insoluble particles are evenly distributed throughout the other substance

31
Q

what are the four types of emulsions of lipids

A

water in oil or oil in water, temporary or permanent

32
Q

what are examples of water in oil and oil in water emulsions

A

water in oil eg butter, oil in water eg milk or mayonnaise

33
Q

what is a temporary emulsion

A

if left to stand, they will separate eg oil vinegar vinaigrette

34
Q

what is a permanent emulsion

A

formed when an emulsifier is added to two immiscible liquids preventing them from seperating eg oil + vinegar + lecithin in egg yolk to make mayonnaise

35
Q

what are the components of emulsifiers

A

a hydrophilic head and hydrophobic tail

36
Q

what are stabilisers of lipids

A

long chained molecules that help maintain emulsions by separating oil droplets culinary app: gums are used to stabilise yogurt

37
Q

what is hydrogenation

A

occurs when hydrogen gas is forced through the double bond of unsaturated fatty acids in the presence of a nickel catalyst, this converts unsaturated oil into a saturated solid fat. culinary app: margarine

38
Q

what is rancidity of lipids

A

the spoilage or decomposition of lipids, creates an unpleasant odour and taste, there is oxidative and hydrolytic rancidity

39
Q
A
40
Q

how do you prevent rancidity of lipids

A

manufacturers add antioxidants naturally eg vitamin A or artificially BHA as they combine with oxygen making it unavailable to attach the carbon at the double bond

41
Q

what is plasticity of lipids

A

describes how soft and malleable a fat is, it is determined by the degree of saturation

42
Q

what are the biological functions of lipids

A

supplies the body with heat and energy for cell activities and helps maintain body temp (37), form a protective layer around delicate organs, supply body with fat soluble vitamins(ADEK), provide body with essential fatty acids and excess stored as adipose tissue as an energy reserve that insulates.

43
Q

what is the total fat intake for adults and saturated fat intake per day

A

no more than 70g per day, 30g of saturated fat for men and 20g for women, fat should be less than 20% of total intake

44
Q

how many kcal in one gram of a lipid

A

9kcal

45
Q

what are disorders link with lipids

A

obesity, coronary heart disease, high cholesterol and strokes

46
Q

how are lipids digested

A

chewed into small pieces in the mouth, melted in the stomach from the heat, liver secretes bile in the duodenum via bile duct which emulsifies large fat molecules into smaller ones, the pancreas secretes pancreatic juice which contains lipase which breaks down lipids into fatty acids and glycerol, the small intestine secretes intestinal juice in the ileum which contains lipase which further breaks down lipids into fatty acids and glycerol

47
Q

how are lipids absorbed

A

they pass through the wall of the villi into the lacteals which are part of the lymphatic system, this transports digested lipids to the thoracic duct where they are deposited through the subclavian vein, this transports the fatty acids and glycerol to the liver