Lipids Flashcards
What is the chemical structure of lipids
Lipids are composted of triglycerides.
triglyceride contains:1 glycerol molecule & 3 fatty acid molecules.
- Glycerol molecule
- Glycerol is a trihydric alcohol.
- It contains: 3 hydroxyl OH groups - Fatty acid molecule
- A fatty acid is an organic compound that contains a carboxyl group [COOH] attached to an R group - Chemical structure of a triglyceride molecule
- Each hydroxyl group (OH) of the glycerol molecule combines with the hydrogens (H) from the faHy acid resulLng in:
o Loss of three water molecules
What are essentials amino acids 3 sources and two functions
Essential amino acids cannot be manufactured by the body and must be obtained by food
Linoleic acid is most important because linolenic acid and arachidoine acid can be manufactured from it in the body
Sources: nuts seeds and olive oil
Functions: build cell membranes essential for growth
Reduces the risk of CHD by raising HDL which removes cholesterol from the blood and lowered lDL
What are omega 3 fatty acids 3 sources and three functions
Have a double bond between the third and fourth carbon atom along with a hyrdrocarbon chain
Sources:oily fish , fish oils , seeds
Functions: reduces risk of CHD heart attach and stroke by faising HDL and lowering LDL
Prevents clots/blockages in coronary arteries
AIDS foetal Brain development during pregnancy
Improves memory and cognitive functioning
Saturated fatty acids and examples
Each carbon atom is saturated with hydrogen
•There are no double bonds present between the carbon atoms
•They are generally solid at room temperature
•They are generally from animal sources
•Examples: Butyric Acid in butter and Stearic Acid in meat
Mono saturated fatty acids and examples
Each carbon atom is not saturated with hydrogen
•There is one double bond present
•These fatty acids are soft or liquid at room temperature
•They originate from plant sources
•Example: oleic acid found in olive oil
Polyunsaturated fatty acid and examples
Each carbon atom is not saturated with hydrogen
•There is more than one double bond present
•These fatty acids are soft or liquid at room temperature
•They originate from plant/marine sources
•Examples include linoleic acid in corn oil and linolenic acid in vegetable oil
What are cis fatty acids
Food sources
Health effects
Cis fatty acids occur when the hydrogen atoms are at the same side of the double bond
Sources - olive oil and fish
Health effects - generally good for health as they raise HDLand lower LDL decreasing chance of CHD
What are trans fatty acids
Food sources
Health effects
Trans fatty acids occur when hydrogen atoms are on the opposite side of the double bond
Sources: foods that contains hydrogenated fats such as pastries and crisps
Health effects- bad for health as they lower HDL and raise LDL increasing risk of CHD
What are the 7 properties of lipids
Solubility Absorbs flavour Heating lipids Emulsions Hydrogenation Rancidity Plasticity
What is oxidative rancidity and hydrolytic rancidity
Oxidative
•This form of rancidity occurs when oxygen is forced through the double bond of an unsaturated fatty acid. It is the most common form of rancidity
Hydrolytic
Occurs when enzymes or bacteria break down lipids into glycerol and fatty acids
Results in unpleasant odour and taste
What is the role of emulsifiers
Molecules that have a hydrophilic head and a hydrophobic tail
When an emulsifier is added to a mixture of two immiscible lipids the hydrophilic head attaches itself to the water and the hydrophobic tail attaches itself to the oil
This prevents the lipids from separating
Heating point
Melting point
•Solid fats melt when heated
•FATS: 30-40˚C
Smoke point
•Lipids begin to decompose to gylcerol & 3 fatty acids
•A blue haze emerges
•An acrid-smelling compound known as acrolein is present
•FATS: 200˚C
•OILS: 250˚C
Flash point •The decomposition of the lipids continues •Lipids spontaneously burst into flames •FATS: 310˚C •OILS: 325˚
What are emulsions
A colloidal solutions formed when two immiscible lipids are forced to mix together they can be water in oil emulsions or oil in water emulsions
Water in oil emulsion: eg butter. Tiny droplets of water is dispersed through oil
Oil in water emulsions: eg milk. Tiny droplets of oil is dispersed through water
Can be temporary or permanent
A temporary emulsion occurs when oil and vinegar are forced together, e.g. French dressing – this is caused by shaking & will seperate on standing
3.A permanent emulsion occurs when oil & water are forced together in the presence of an emulsifier, eg. Mayonnaise
Culinary application of emulsifiers
Lecithin found in egg yolks used to produce mayonnaise
What is hydrogenation
Hydrogenation occurs when hydrogen is forced through the double bond of unsaturated fatty acids in the presence of a nickel catalyst
Used in the production of margarine
