Lipids Flashcards
What is the main structure of fatty acids?
- A long hydrocarbon chain which is hydrophobic.
- A carboxylic acid group which is ionised in solution and extremely hydrophilic
What are fatty acids readily able to react with?
Second molecule
A hydroxyl or an amino group on a second molecule to form esters and amides.
How does the top part of fatty acids act?
- It acts as a carboxylic acid the same as in amino acids.
- It can react with other amines to make an amide or with alcohols to make an ester.
How stable are fatty acids?
Chemically reactive
They are most stable in a zig-zag line and aren’t very chemically reactive due to their stability.
What is the negative charge on the oxygen good for?
- It creates a strong electrostatic charge.
- It’s a really good hydrogen bond acceptor due its polarity.
How are phospholipids and fatty acids tied together?
Covalent bonds
What does the tail of fatty acids prefer?
Aggregate
The tail prefers fatty things and likes to be away from water.
It’s non-polar and repels water and seeks to aggregate with other hydrophobic units.
What does the head do?
The head likes water and is most stable in water.
It’s polar and forms hydrogen bonds with water.
What problem do amphiphiles have?
Favourable
- They have two conflicting forces from the hydrophobic tail and the hydrophilic head.
- They overcome this by aggregating in energetically favourable arrangements in which the head sits in a polar environment and the tails come together to create an apolar environment.
What is the best arrangement for tails?
Optimises
The best arrangements of tails involve close packing which optimises van der Waals interactions but few strongly directing interactions (electrostatics, H-bonding)
What is the common general structure that biological membranes have?
Impermeable
- The lipid molecules are arranged as a continuous double layer about 5 nm thick.
- This lipid bilayer provides the basic fluid structure of the membrane and serves as a relatively impermeable barrier to the passage of most water-soluble molecules – less polar molecules can pass
What molecules can easily pass through a biological membrane?
Hydrophobic molecules due to van der waals forces.
Why are individual phospholipids able to rotate and what rotation is very rare?
- The van der Waal forces are very similar for each interaction.
- Complete flipping of the lipids rarely occurs as it is energetically unfavourable as it would require the head group to pass through the non-polar layer.
Why is fluidity of the membrane important?
Distribution
- It allows molecules to enter and leave the cell easily.
- Allows the membrane to fuse
- Allows for even distribution if the cell is splitting the outside molecules can organise to make sure they’re split evenly into 2 new cells.
What factors effect fluidty?
Length
- The length of the hydrocarbon tails. Shorted reduced interactions of the hydrocarbons make it more fluid.
- Saturation - each double bond in an unsaturated tail created a small kink.