Lipids Flashcards
What elements make up lipids ?
C, H, O
Are lipids soluble in water and organic solvents ?
Insoluble in water
Soluble in organic solvent
Are lipids polar or non-polar ?
Non-polar and hydrophobic
What are the three groups of lipids ?
Simple lipids
Complex lipids
Steroids and sterols
How are simple lipids formed ?
By joining fatty acids to an alcohol by ester linkages
Eg. Triglyceride, waxes
What are complex lipids made up of ?
A lipid and a non-lipid component
Eg. Phospholipids, glycolipids
What are steroids and sterols characterised by ?
Carbon skeleton consisting of four fused rings (steroid nucleus)
Eg. Cholesterol
What is a glycerol ?
An alcohol with three -OH groups
Are glycerols soluble water ?
Yes - the OH groups can interact with water
What are fatty acids ?
Long chained carboxylic acids contain an even number of carbon atoms
- consist of a long hydrocarbon chain (fatty acid tail) and a carboxylic acid group
Which parts of te fatty acid are hydrophobic, which are hydrophilic ?
Long hydrocarbon chain is hydrophobic
Carboxylic acid is hydrophilic
What does the melting point of difference fatty acids depend on
The degree of saturation and the length of the hydrocarbon chain
What are saturated fatty acids ?
No C=C
Each carbon has maximum number of H atoms attached
What are unsaturated fatty acids ?
C=C present creating a ‘kink’ in hydrocarbon tail
As number of C=C increase, does MP increase or decrease ?
Decrease
Why does MP decrease as number of C=C increase ?
Greater number of C=C means greater number of kinks
There is thus weaker intermolecular interaction between fatty acid molecules, lesser energy is required to weaken the hydrophobic interactions
As length of hydrocarbon tail increase, does MP increase or decrease ?
Increase
Why does MP increase when length of hydrocarbon tail increase ?
The longer the tail, the larger the surface area available for hydrophobic interactions between the hydrocarbon chains thus larger amounts of energy needed to weaken the interactions
What makes up a triglyceride ?
1 glycerol + 3 fatty acids
What is the bond joining the fatty acids to the glycerol in triglyceride ?
Ester bond
How is triglyceride formed ?
Condensation reaction where a molecule of water is removed to form -COO- (ester bond)
What are the five functions of triglyceride ?
- Storage form of energy
- Source of metabolic water
- Good thermal insulator (blubber)
- Provides buoyancy to aquatic mammals
- Protective layer for delicate internal organs
What properties of triglyceride allows it to be a good storage material ?
Large and uncharged hence insoluble in water
- can be stored in large amounts without affecting WP of cell and can be prevented from diffusing out of cells
Why is triglyceride a good store of energy ?
For the same weight, triglycerides yields twice the quantity of energy compared to carbs
- lipids are more reduced than carbs, more oxidation steps are needed to fully oxidise lipids thus more ATP formed
What is metabolic water ?
Water produced from oxidation of food, very important to desert animals
Why are triglycerides a good source of metabolic water ?
Triglycerides yield 2x more H atoms than carbs thus better source of water
- H atoms give water upon oxidation
Why is triglyceride a good thermal insulator ?
Prevents excessive heat loss, important in aquatic animals
Why does triglyceride provide buoyancy to aquatic animals ?
It is less dense than water
what are phospholipids made out of ?
1 glycerol + 2 fatty acids + a phosphate group (negatively charged)
How is phospholipids formed ?
Through 2 condensation reactions
- one where fatty acid is joined to glycerol, forming ester bond and producing 1 mole of water
- one where phosphate group is joined to glycerol, forming phosphoester bond and producing water
What is a phospholipid ?
A complex lipid
A major component of cell membrane
Are phospholipids hydrophobic or hydrophilic ?
They are amphipathic (both hydrophobic and hydrophilic regions present)
- hydrocarbon tails are hydrophobic
- phosphate heads are hydrophilic
What are the 4 functions of phospholipid ?
Form a bilayer due to their amphipathic nature
Allows for compartmentalisation (separation) of cell contents from aqueous external cell environment
Allows for formation of organelles within cell where specialised biochemical reactions occur
Variations of phospholipids affect fluidity and thus permeability of membrane
What is the structure of the phospholipid bilayer ?
Polar, hydrophilic heads point outwards and make contact with water molecules
Non-polar, hydrophobic hydrocarbon tails point inwards, forming hydrophobic core
How is a variety of phospholipids formed ?
Addition of small molecules to the phosphate group
Degree of saturation
Length of fatty acids
