Unit 1 - Lipids Flashcards
What are the 2 groups of lipids?
Triglycerides and phospholipids.
How are triglycerides formed?
By the condensation of 1 molecule of glycerol and 3 fatty acid molecules.
Why are triglycerides not a polymer?
Because it is not made of the same repeating monomers.
Structure of a glycerol molecule?
Structure of a fatty acid chain?
What bond forms when a glycerol bonds with a triglyceride molecule?
An ester bond. So in the formation of a triglyceride molecule 3 ester bonds are produced.
What makes lipids insoluble in water?
The fatty acid tails are hydrophobic which means they repel water. This means they can form insoluble droplets. The fatty acid tails face inwards shielding them from water with their glycerol heads.
What does the letter ‘R’ represent?
The variable hydrocarbon chain. Shortens it as it is very long.
What are saturated fatty acids?
They have single bonds between carbon atoms in the hydrocarbon chain.
What are unsaturated fatty acids?
They have double bonds between the carbon atoms in the hydrocarbon chain.
Structure of a triglyceride molecule?
Definition of monounsaturated?
One double bond
Definition of polyunsaturated?
More than one double bond.
Structure of a phospholipid?
A glycerol molecule bonded to 2 fatty acid molecules and 1 phosphate group.
How are phospholipids formed?
Condensation reactions.
Why are phosphate heads hydrophilic?
Because the negative ion (phosphate group) is attracted to the slightly positive water molecules.
Phospholipids form a what in water?
Bilayer.
How many ester bonds form in a phospholipids molecule?
Only 2 as there are only 2 fatty acid molecules that bind to the glycerol. An ester bond DOES NOT form between the glycerol molecule and the phosphate head.
Formation of the phospholipid bilayer?
The hydrophobic fatty acid tails are arranged in the middle away from the water and the hydrophilic phosphate heads are arranged on the outside in contact with the water.
What is a bilayer used in
Cell surface membranes.
Uses of triglycerides?
Commonly found in food and are used for energy storage.
Uses of phospholipids?
They help to form the cell membranes of cells.
How is the structure of triglycerides related to its function?
Long hydrocarbon fatty acid chains-contains lots of stored chemical energy-used as an energy storage molecule.
Hydrophobic fatty acid tails-insoluble in water (form insoluble droplets, with fatty acid tails in and glycerol heads out)-does not affect the water potential of cells/will not dissolve (and release whatever energy they were storing) when in contact with water.
How is the structure of phospholipids related to its function?
Hydrophobic fatty acid tails and hydrophilic phosphate heads-will form a phospholipid bilayer with hydrophobic fatty acid tails pointing in away from the water and hydrophilic phosphate heads pointing towards the water-forms cell membranes. The hydrophobic fatty acid centre means that water soluble molecules cannot easily pass across the membrane.
What’s the biological test for lipids?
It’s called the emulsion test. You add 2cm3 ethanol and shake (this dissolves the lipids). Then add water drop wise and shake. If lipids is present, a white emulsion will be visible ( this is fat droplets).
