3.5 : Lipids Flashcards
What are lipids?
Commonly known as fats and oil. Molecules that contain carbon, hydrogen and oxygen.
Why are lipids insoluble?
They are non polar molecules, which means that there are no positive or negative regions within the molecules and are therefore insoluble.
What category do lipids fall under ?
Macromolecules
Describe the structure of triglyceride. What categories do it’s components fall under?
One glycerol molecules attached to three fatty acids.
Glycerol = alcohol
Fatty acids = carboxylic acid
How are the glycerol and fatty acids bonded?
Through condensation reactions which remove the OH groups of the glycerol and fatty acids. This forms an ester bond. The whole process is called esterification.
How do you break down triglycerides?
Through hydrolysis reactions, which returns the OH groups.
How does saturation affect the state of fatty acids at room temperature?
The presence of one double or more causes it to kink and bend. This means it can’t be packed closely together, and is therefore liquid at room temperature. They are then called oils rather than fats.
What are phospholipids?
Modified triglycerides that contain a phosphate group.
Describe the structure of phospholipids
It has a non polar tail ( fatty acid ) which is repelled by water and is therefore hydrophobic. It has a charged head ( phosphate group ) which will interact with and is attracted to water, and is therefore hydrophilic.
Why are phospholipids called surface active agents or surfactants ?
They form a layer on the surface of water, with the charged phosphate head in the water and hydrophobic fatty acids tails sticking out of it.
What is a phospholipid bilayer? Why is it important to cell membranes?
All their hydrophobic tails point toward the centre of the sheet, protected from the water by the hydrophilic heads.
Important because they are able to separate an aqueous environment in which cells usually exist from the aqueous cytosol within cells.
What are sterols / steroid alcohols ?
Another type of lipid found in cells. Complex alcohol molecules.
They have dual hydrophilic / hydrophobic characteristics. The hydroxyl group is polar and therefor hydrophilic and the rest of the molecule is hydrophobic.
What is the function of cholesterol ?
- role in the formation of cell membranes
- this adds stability to cell membranes and regulates fluidity by keeping them fluid at low temps and stopping them becoming too fluid at high temps
What is manufactured using cholesterol?
Vitamin D
Steroid hormones
Bile
What are the roles of lipids ?
- membrane formation and creation of hydrophobic barriers
- hormone production
- electrical insulation necessary for impulse transmission
- waterproofing eg birds feathers, plant leaves
