Module 2: Biological Molecules - Lipids. Flashcards
What are Lipids?
Lipids are macromolecules.
Are biological molecules which are only soluble in organic solvents such as alcohol
What chemical elements do Lipids contain?
Carbon.
Hydrogen.
Oxygen.
What are the three types of Lipids?
Triglycerides.
Phospholipids.
Cholesterol.
What are Triglycerides?
They contain a molecules of glycerol bonded to three fatty acids molecules.
They’re synthesised by the formation of an ester bond between each fatty acid and the glycerol molecule.
They are NON polar molecules. (Hydrophobic).
They are insoluble - They do not dissolve in water.
What is Esterification?
It is the process in which triglycerides are synthesised.
Explain the Ester bonds within a triglycerides
One Triglyceride molecule has 3 ester bonds. Each ester bond is formed by a condensation reaction - in which a water molecule is released.
Triglycerides breakdown when the ester bonds are broken. Each ester bond is broken in a hydrolysis reaction - in which a water molecule is used up.
Describe Fatty acid molecules.
Fatty acid molecules have long ‘tails’ made of hydrocarbons.
The tails are hydrophobic.
These tails make lipids insoluble in water
All fatty acids have the same structure, however the hydrocarbon tail varies.
What are the 2 kinds of Fatty acids?
Saturated.
Unsaturated.
What is the difference between Saturated Fatty acids and Unsaturated Fatty acids?
Saturated fatty acids =
Do not have any double bonds (single carbon - carbon bonds) atoms in their hydrocarbon tails.
Unsaturated fatty acids =
Have at least one double bond between carbon atom, which causes the chain to kink.
What are Phospholipids?
Phospholipids contain a molecule of glycerol bonded to 2 fatty acids and 1 phosphate group.
The phosphate group is hydrophilic (attracts water molecules) and the tails are hydrophobic
Describe Phospholipids.
(function and structure)
They are found in the Cell membrane of all eukaryotes + prokaryotes.
Phospholipids make up the phospholipid bilayer. They have a hydrophilic head and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side.
The centre of the bilayer is hydrophobic. This means that water soluble substances can not pass through it - the membrane acts as a barrier to those substances.
What is Cholesterol?
It is another type of Lipid.
It has a hydrocarbon ring structure attached to a hydrocarbon tail. The ring structure has a polar hydroxyl (OH) group attached to it.
Describe Cholesterol.
(function and structure)
Cholesterol helps to regulates the fluidity of the cell membrane by interacting with the phospholipid bilayer.
Cholesterol has a small size and flattened shape - this allows Cholesterol to fit in between the phospholipid molecules in the membrane.
At higher temperatures, they bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together. This helps to make the membranes less fluid and more rigid
However at lower temperatures, Cholesterol prevents the phospholipids from packing too close together, and so membrane fluidity increases.
Describe Triglycerides.
(function and structure)
They are insoluble therefore they do not cause water to enter cells via osmosis which would lead to swelling.
The tails are hydrophobic, therefore they face inwards, shielding themselves from the water with their glycerol heads.
