lipids Flashcards
what are fats at room temp
lipids that are solid at room temp
what are oils at room temp
lipids that are liquid at room temp
what are lipids made up of
triglyceride, when one glycerol molecule joins with three fatty acids and three water molecules are eliminated
what is the formula for a fatty acid
CH3(CH2)nCOOH
What differentiates a fatty acid
number of carbon atoms
what are the classifications of fatty acids
saturated, monounsaturated and polyunsaturated
what is saturation in terms of a fatty acid
the amount of hydrogen molecules are present in a fatty acid
what is the structure of a saturated fatty acid
each carbon atom has it full quota of hydrogen, no double bonds between carbon atoms
what are the consistency and melting point of the three fatty acid types
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
what are sources and examples of saturated fatty acids
animal sources, butyric acid in butter, stearic acid in meat
what is the structure of monounsaturated fatty acids
each carbon is not fully saturated with hydrogens and there is one double bond between carbon
what are sources and examples of monounsaturated fatty acids
plant and marine sources, oleic acid in olive oil
what are sources and examples of polyunsaturated fatty acids
plant and marine sources, alpha linolenic acid in seed oil snd linolenic acid in seeds
what is the structure of polyunsaturated fatty acids
each carbon is not fully saturated with full quota of hydrogen and there is more than one double bond between carbons
what are essential fatty aids
cannot be manufactured in the body so must be obtained by food, eg alpha linolenic acid, a type of omega 3
what are the functions of essential fatty acids
aids cell membranes formations, reduces risk of CHD by raising HDL which help remove cholesterol and lower LDLs
what are omega 3 fatty acids
polyunsaturated fatty acids that have a double bond between the third and fourth carbon on the hydrocarbon chain.
what are the two main types of omega 3 fatty acids
EPAs and DHAs
what are sources of omega 3 fatty acids
oily fish and nuts
what are the functions of omega 3 fatty acids
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
what are cis fatty acids
two hydrogen bonds on the same side of the double bond, they are generally good for health by increasing HDL
what are trans fatty acids
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
what are alternatives to saturated fats like butter or lard
fats containing trans fatty acids
what is the function of cholesterol
made in the liver for cell function and hormones, excess however from saturated fatty foods builds up in the arteries
what is artherosclerosis
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
what is a lipoprotein
occurs when cholesterol binds with proteins and either makes high density pr low density lipoproteins
what do HDLs do
mop up loose cholesterol from arteries and carries it back to the liver where it is broken down
what do LDLs do
deposits on the walls of arteries
what are the properties of lipids
solubility, absorption of flavours, heating lipids, emulsions, emulsifiers, hydrogenation, rancidity, plasticity
what is solubility of lipids
insoluble in water but soluble in solvents like benzene
what are the three points of heating lipids
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 .
what is absorption of flavours of lipids
lipids absorb flavours easily, culinary app: infused oils or garlic butter
what is an emulsion of lipids
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
what are the four types of emulsions of lipids
water in oil or oil in water, temporary or permanent
what are examples of water in oil and oil in water emulsions
water in oil eg butter, oil in water eg milk or mayonnaise
what is a temporary emulsion
if left to stand, they will separate eg oil vinegar vinaigrette
what is a permanent emulsion
formed when an emulsifier is added to two immiscible liquids preventing them from seperating eg oil + vinegar + lecithin in egg yolk to make mayonnaise
what are the components of emulsifiers
a hydrophilic head and hydrophobic tail
what are stabilisers of lipids
long chained molecules that help maintain emulsions by separating oil droplets culinary app: gums are used to stabilise yogurt
what is hydrogenation
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
what is rancidity of lipids
the spoilage or decomposition of lipids, creates an unpleasant odour and taste, there is oxidative and hydrolytic rancidity
how do you prevent rancidity of lipids
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
what is plasticity of lipids
describes how soft and malleable a fat is, it is determined by the degree of saturation
what are the biological functions of lipids
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.
what is the total fat intake for adults and saturated fat intake per day
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
how many kcal in one gram of a lipid
9kcal
what are disorders link with lipids
obesity, coronary heart disease, high cholesterol and strokes
how are lipids digested
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
how are lipids absorbed
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