B M 2 : Lipids Flashcards
what are triglycerides made of
- one molecule of glycerol
- 3 fatty acids attached to it
fatty acids tails made of?
- fatty acids have long tails made of hydrocarbons
- tails are hydrophobic
- tails make lipids insoluble in water
all fatty acids have same basic structure, what is it?
O=C-R
/
HO
C= carbon atom links fatty acid to glycerol R= variable R group hydrocarbon tail
whats one thing that varies in the different fatty acids?
hydrocarbon tail
what reaction forms triglycerides?
Condensation reactions
what bond forms between a fatty acid joining to a glycerol molecule?
Ester bond
what is released when an ester bond is formed?
A water molecule (as it’s a condensation reaction)
how many times does a glycerol molecule join to a fatty acid to produce a triglyceride?
3 times
what are the two types of fatty acid?
Saturated or unsaturated
what causes the difference between saturated and unsaturated?
The hydrocarbon tails (R group)
structure of saturated fatty acids?
- Don’t have any double bonds between their carbon atoms
- fatty acid is saturated with hydrogen
structure of unsaturated fatty acids?
- have at least one double bond between carbon atoms
- causes chain to kink
what are the lipids found in cell membranes?
phospholipids
whats the difference between phospholipids an triglycerides?
- similar except one fatty acid molecule is replaced with a phosphate group
which parts of phospholipids are hydrophobic and hydrophilic
hydrophobic = fatty acid tails hydrophilic = phosphate group
what does the structure of lipids relate to?
Their functions
what are triglycerides mainly used as?
energy storage molecules
1 reason why triglycerides are good as energy storage molecules?
- long hydrocarbon tails of fatty acids contain lots of chemical energy when they’re broken down
- because of this lipids contain twice as much energy per gram as carbhydrates
another reason why triglycerides are good as energy storage molecules?
- insoluble, so don’t affect water potential of the cell and cause water to enter the cell by osmosis
- triglycerides clump together as insoluble droplets in cells because fatty acid tails are hydrophobic = tails face inwards. shielding themselves from water with their glycerol heads
what do phospholipids make up?
the bilayer of cell membranes
1 reason why phospholipids are good as a bilayer?
- heads hydrophilic and tails hydrophobic, so form a double layer with their heads facing out towards the water on either side
another reason why phospholipids are good as a bilayer?
center of bilayer is hydrophobic, so water-soluble substances can’t easily pass through it - membrane acts as a barrier to those substances
what test can test for lipids?
Emulsion test
how to perform the emulsion test
1) shake substance with ethanol so it dissolves, the pour solution into water
2) any lipid will show up as a milky solution
3) the more lipid there is the more noticeable the milky colour will be
