GRE Subject Test: Chemistry : Lipids
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Example Questions
Example Question #1 : Lipids
Which of the following molecules is amphipathic?
Phospholipid
Triglyceride
Glutamate
Maltose
Phospholipid
Amphipathic molecules contain both polar and nonpolar regions, making them an extremely diverse class with an array of functions. For example, bile is an amphipathic molecule whose nonpolar region interacts with fats and whose polar region interacts with the aqueous environment of the small intestine.
Most lipids are entirely nonpolar and hydrophobic. Phospholipids, however, are formed from a glycerol molecule bound to two hydrophobic fatty acid tails and a hydrophilic phosphate head. This structure allows phospholipids amphipathic properties. Most notably, phospholipids are able to interact with the aqueous environments in the cell cytosol and extracellular environment, while maintaining the hydrophobic region of the cell membrane that acts as a semipermeable barrier.
Triglycerides are considered nonpolar. Glutamate is an acidic amino acid with highly polar properties. Maltose is a six-carbon sugar (carbohydrate) and is highly polar.
Example Question #1 : Properties Of Lipids
Which of the following will you most likely find in a steroid molecule?
Cyclohexane ring
Pentose sugar
Nitrogenous base
Phosphate group
Cyclohexane ring
Steroids are a type of lipid that are characterized by their four-ring molecular structure. The four rings consist of three six-membered rings and one five-membered ring. Recall that six-membered rings are called cyclohexanes and five-membered rings are called cyclopentanes; therefore, you will most likely find a cyclohexane in a steroid.
Phosphate groups, pentose sugars, and nitrogenous bases are found in nucleotides, which are monomers that make up nucleic acids. Steroids are a type of lipid; therefore, you will most likely not find these substances in a steroid.
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