4. Lipids Flashcards
Give an example of a lipid?
Triglyceride.
What is the structure of a triglyceride?
One molecule of glycerol with 3 fatty acids attached to it.
What is the structure of a fatty acid molecule?
Long tails made of hydrocarbons.
The tails are hydrophobic (repel water) makes them insoluble in water.
All have the same basic structure but hydrocarbon tail varies.
What is the basic structure of a fatty acid? diagram
Carbon atoms links fatty acid to glycerol.
Variable R group hydrocarbon tail.
How is a triglyceride formed?
When a fatty acid joins to glycerol molecule.
Ester bond is formed, a molecule of water is releases - its a condensation reaction.
Process happens twice more to from triglycerides.
Name the 2 kinds of fatty acid?
Saturated.
Unsaturated.
Difference is in their hydrocarbon tails - r group.
What are saturated fatty acids?
Don’t have any double bonds between their carbon atoms.
Fatty acid is saturated with hydrogen - maximum saturation.
Form straight chains
What are unsaturated fatty acids?
Have atleast one double bond between carbon atoms, causing chain to kink.
More double bonds the more it’s bent
What are the lipids found in cell membranes called?
Phospholipids.
What are phospholipids?
Similar to triglycerides except one of the fatty acid molecules is replaced by phosphate group.
What is a phosphate group?
Its hydrophilic (attracts water). The fatty acid tails are hydrophobic (repel water). This is important in the cell.
What are triglycerides mainly used for?
Energy storage.
Why are triglycerides good for energy storage?
Long hydrocarbon tails of the fatty acids contain lots of chemical energy - lots of energy released when broken down.
They’re insoluble so don’t affect water potential of the cell and cause water to enter cells by osmosis.
How much energy do lipids contain?
Twice as much energy per gram as carbohydrates.
What do the triglycerides clump into?
A insoluble droplets in cells because the fatty acid tails are hydrophobic - tails face inwards, shielding them from the water with their glycerol heads.
What do phospholipids make up?
The bilayer of cell membranes.
Cell membranes controls what enters and leaves the cell.
Structure of phospholipids?
Heads are hydrophilic and tails ate hydrophobic so they form double later with heads facing out towards water.
Centre of bilayer is hydrophobic so water-soluble substances can’t pass through it easily.
What is the emulsion test for lipids?
To find fat in a food use the emulsion test.
Shake the test substance with ethanol for 1 minute so it dissolves, then pour solution into water.
Lipid will show up as milky emulsion.
More lipid=more noticeable milky colour is.
What are phospholipids made up of ?
1 glycerol
2 fatty acids
1 inorganic phosphate
What TYPE of properties do phospholipids have ?
Amphiphillic
What are the phospholipids droplets which exclude water, called ?
Micelle
And
Bilayers
What elements do lipids contain ?
Carbon
Hydrogen
Oxygen
Example of triglycerides
Fats - solid at room temp
Oils - liquid at room temp
How many ester bonds form in triglycerides
3
After water is removed
Hydrolysis of triglycerides
Add 3 molecules of water to break ester bond
This produces 3 fatty acid molecules and 1 glycerol molecule
What does saturation refer to ?
Hydrogen
More “full of hydrogen” the hydrocarbon chain is the more saturated fatty acid is
Not fully saturated then doubly bonds form between carbon atoms
What will a triglycerides with all saturated fatty acids forms ?
Fat
Solid
Mono saturated fatty acid
1 carbon double bond
What will triglycerides be with all unsaturated fatty acids?
Oil
Can’t compact as tight together
