GRE Subject Test: Biochemistry, Cell, and Molecular Biology › Help with Lipids
Which type of lipid acts as a buffer for membrane fluidity?
Sterols
Phospholipids
Glycolipids
Terpenes
Membrane fluidity can be buffered by cholesterol in both warm and cold environments. At high temperatures cholesterol raises the melting point, while at lower temperatures cholesterol prevents the formation of crystalline structures between phospholipids.
Phospholipids are comprised of __________.
a glycerol head containing a phosphate group and two fatty acids
a glycerol head containing a phosphate group and three fatty acids
a glycerol head and two sphingolipids
a sugar, phosphate group, and nitrogenous base
a chain of saturated fats
The correct answer is a glycerol head containing a phosphate group and two fatty acids. Phospho refers to the phosphate group and lipid refers to the glycerol backbone attached to two fatty acid chains.
What qualifies a molecule to be considered an omega-3 fatty acid?
The presence of a double bond on the third-to-last carbon in the fatty acid
The presence of a double bond on the third carbon in the fatty acid
The presence of three double bonds in the fatty acid
The attachment of three of the same fatty acid to a glycerol
Omega-3 fatty acids are named after the double bond that starts on the third-to-last carbon in the fatty acid. The carboxylic acid carbon is considered the first carbon, while the last methyl group carbon is considered the "omega" carbon. As a result, the double bond will be three carbons away from the end.