GRE Subject Test: Biology : Understanding Lipids
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Example Questions
Example Question #1 : Understanding Lipids
Which of the following requires a carrier protein in order to be transported through the bloodstream?
Glycine
Sucrose
Steroid
ATP
Steroid
Blood is an aqueous solution and will easily dissolve polar, hydrophilic molecules. Nonpolar molecules, however, do not easily exist in this solution and require a bound polar group, such as a carrier protein, to exist in equilibrium.
Proteins, carbohydrates, and nucleic acids all contain polar groups, allowing them to dissolve in the blood. Lipids, however, are nonpolar and require transport proteins. Steroids are a class of lipids and will require protein assistance for transport in the blood.
Sucrose is a carbohydrate, glycine is a polar amino acid, and ATP is a polar nucleic acid derivative.
Example Question #23 : Cell Biology
Which of the following molecules is amphipathic?
Phospholipid
Glutamate
Triglyceride
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 #3 : Other Macromolecules
Which of the following lipid classifications has the primary purpose of storing energy for the body?
Glycerolipids
Sterols
Glycolipids
Glycerophospholipids
Glycerolipids
Lipids have a variety of functions in the human body, one of which is the storage of energy for later use. This function is accomplished by triglycerides (also called triacylglycerols), which belong to the class of glycerolipids.
Example Question #1 : Other Macromolecules
Fatty acids can vary in length. Which of the following fatty acids chains cannot not be synthesized in the human body?
A fourteen-carbon fatty acid chain
A twenty-four-carbon fatty acid chain
A nineteen-carbon fatty acid chain
A twelve-carbon fatty acid chain
An eighteen-carbon fatty acid chain
A nineteen-carbon fatty acid chain
Fatty acids synthesized in the human body always have an even number of carbon atoms usually between 12 and 28. Odd-numbered fatty acid chains will occasionally be found in plants and marine animals.
Example Question #2 : Other Macromolecules
A phospholipid contains which of the following components?
I. Fatty acids
II. Phosphate
III. Sulfate
IV. Glycerol
II and IV
I, III, and IV
I, II, and IV
I and IV
I and II
I, II, and IV
A phospholipid is made up of two fatty acids and a phosphate group with an R-group attached to a glycerol backbone. The phosphate group allows for one end of the molecule to be polar while the fatty acids allow for the other part to be nonpolar. Phospholipids are a major component of the bilayered cellular membrane
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