Lipids - sterols, role of lipids Flashcards
What are sterols?
Also known as steroid alcohols
Another type of lipid found in cells.
They are not fats or oils and have little in common with them structurally
What are the properties of sterols?
They are complex alcohol molecules based on a four carbon ring structure, with a hydroxyl group at one end.
Like phospoholipids, they have a dual hydrophillic/hydrophobic characteristics.
The hydroxyl group is polar and therefore hydrophillic and the rest of the molecule is hydrophobic.
What is an example of a sterol?
Cholestrerol.
It has an important role in the formation of cell membranes, becoming positioned between the phospholipids with the hydroxyl group at the periphery of the membrane
This adds stability to the membrane and regulates fluidity at different temperatures.
What cholseterol also produce?
Vitamin D, steroid hormones, and bile.
How does the non-polar nature of lipids make them useful?
Membrane formation and the creation of hydrophobic barriers.
Hormone production.
Electrical insultion - necessary for impulse transmission.
Waterproofing, for example in birds feather and on plant leaves.
What are the other uses of lipids in terms of storage?
Stored around vital organs and under the skins for energy.
Thermal insulation to reduce heat loss
Cushioning to protect vital organs such as the heart and kidneys
Buoyancy for aquation animals e.g. whales.
How are lipids identified?
Emulsion test
Sample is mixed with ethanol
Resulting solution is mixed with water and shaken.
If a white emulsion forms as a layer on top of the solution this indicates the presence of a lipid.
If the solution remains clear the text is negative.
