Lipids

Question	Answer
What other names are lipids known by?	Fats and oils
Generally, which elements are lipids made up of?	Carbon, hydrogen and oxygen
What is the state of most lipids at room temperature?	The lipids known as 'fats' are often solid at room temperature and the lipids known as 'oils' are liquid at room temperature
Are lipids polar?	No, lipids are not polar. The electrons in lipids are more evenly distributed than in carbohydrates and other polar molecules. For this reason, lipids are not soluble in water.
What is the general structure of a lipid?	They are not made up of monomers like most sugars are, but instead, are large complex molecules.
What is a triglyceride?	A lipid made from combining a glycerol with three fatty acids. A glycerol is a type of alcohol and fatty acids are carboxylic acids (have a -COOH group)
In triglycerides, how do the glycerol and the fatty acids bond?	Both the glycerol and the fatty acids have OH groups. As there are three fatty acids and three OH groups on the glycerol, three condensation reactions occur to bond the three fatty acids to the glycerol. This releases three water molecules.
What is the bond created by the condensation reaction that joins glycerol to fatty acid?	An ester bond. The ester bond includes the oxygen, first carbon, and the double bond to the oxygen in the fatty acid.
What is a saturated fatty acid chain?	A chain that has no double bonds in it. Saturated means there is no space for extra bonds to occur.
What is a mono-unsaturated fatty acid?	A fatty acid that has one double bond in it. This double bond can be opened up and another bond can occur along the fatty acid chain.
What is a poly-unsaturated fatty acid chain?	A fatty acid chain that has multiple double bonds along it.
What are the differences between saturated and unsaturated fatty acids?	Saturated fatty acids can pack more closely together because unsaturated fatty acids can kink and bend, meaning they don't tessellate as well as saturated ones. Due to not packing together as well, unsaturated fats are often oils (liquid at room temperature) whilst saturated fats are solid.
What is a phospholipid?	A phospholipid is a triglyceride that also has the element phosphorus in it, alongside the carbon, hydrogen and oxygen. Phosphate ions are polar so are soluble. In a phospholipid, one of the fatty acid chains are replaced with a phosphate.
Are phospholipids polar?	Somewhat, yes, they have a hydrophilic head (charged head) and a hydrophobic tail. This is due to the phosphate being polar and their long length.
How do phospholipids interact with water?	The charged heads are attracted to water, so will form a layer on the surface of the water with their hydrophobic tails projected away from the water. This is why they are ideal for cell membranes.
What are Sterols?	Sterols, or steroid alcohols, are not fats or oils and have little in common with them structurally. They are complex alcohol molecules with an OH group at one end. This gives them hydrophilic/hydrophobic properties, like phospholipids.
What is cholesterol?	Cholesterol is a steroid alcohol (sterol). It is produced in the liver and intestines and has an important role in forming cell membranes. Cholesterol is situated in the cell membrane to maintain its fluidity. Cholesterol has a role in manufacturing vitamin D, steroid hormones and bile.
What biological roles do lipids play?	Membrane formation, insulation of electrical impulses in the nervous system (myelin), hormone production and waterproofing (in leaves on trees and birds feathers)
What are the roles of lipids in energy storage?	Thermal insulation to reduce heat loss, cushioning to protect vital organs, buoyancy in aquatic animals.
How can you test for lipids?	An emulsion test. This involves mixing the sample with ethanol. The resulting solution is mixed with water and shaken. If a lipid is present, a white emulsion forms on top of the solution.
Are unsaturated or saturated fats more healthy for us?	Unsaturated

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	Created by Emma Lloyd over 7 years ago