All GRE Subject Test: Biology Resources
Example Questions
Example Question #21 : Macromolecules
Once a G-protein coupled receptor (GPCR) has bound to its ligand, which of the following steps allows the subunit to dissociate from the receptor and trigger downstream cascades?
Degradation of the GPCR's C-terminal tail that is bound to the unit
None of these
Exchanging the G-protein's association with a magnesium ion for a calcium ion
Exchanging the G-protein's bound ADP for an ATP
Exchanging the G-protein's bound GDP for a GTP
Exchanging the G-protein's bound GDP for a GTP
The G-proteins associated with the intracellular terminal of a GPCR dissociate when the change in conformation of the G-protein allows for a GTP to replace a GDP bound to the G-protein. ATP and ions are not at play here, nor is there degradation of the receptor's intracellular tail. It is the binding of GTP alone that triggers the cascading results of the protein's activation.
Example Question #22 : Macromolecules
Toll-like receptors (TLRs) are known for their role in innate immunity in humans and in many other organisms. How do these receptors induce downstream signaling to induce an innate immune response?
Recognition of pathogen-associated molecular patterns (PAMPs)
Recognition of coagulation factors (platelet clotting factors)
Recruitment of macrophages
Recognition and dimerization of integrins
Recruitment of natural killer cells
Recognition of pathogen-associated molecular patterns (PAMPs)
TLRs are transmembrane receptors that have an extracellular leucine-rich region that recognize PAMPs. Recognition of a pathogen factor causes the intracellular toll-interleukin-1 domain to bind adaptor proteins to induce expression of genes responsible for initiating an innate immune response.
Example Question #23 : Macromolecules
Paracrine signaling refers to which type of cell signaling?
Cell signaling across a synapse
Same cell signaling
Long range cell signaling
Intracellular signaling
Close range cell signaling
Close range cell signaling
Paracrine signaling refers to close range cell to cell signaling. This is different from endocrine signaling in which signaling molecules (hormones) are released into the blood stream in order to communicate with distant cells.
Autocrine signaling is a type of signaling in where the signaling molecule and the receptor for that messenger are found on the same cell. Cell signaling across a synapse is called synaptic signaling.
Example Question #24 : Macromolecules
Which of the following requires a carrier protein in order to be transported through the bloodstream?
Glycine
Sucrose
ATP
Steroid
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 #25 : Macromolecules
Which of the following molecules is amphipathic?
Glutamate
Maltose
Triglyceride
Phospholipid
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 #26 : Macromolecules
Which of the following lipid classifications has the primary purpose of storing energy for the body?
Glycolipids
Glycerolipids
Glycerophospholipids
Sterols
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 #27 : Macromolecules
Fatty acids can vary in length. Which of the following fatty acids chains cannot not be synthesized in the human body?
A twenty-four-carbon fatty acid chain
A nineteen-carbon fatty acid chain
A fourteen-carbon fatty acid chain
An eighteen-carbon fatty acid chain
A twelve-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 #28 : Cell Biology
A phospholipid contains which of the following components?
I. Fatty acids
II. Phosphate
III. Sulfate
IV. Glycerol
I, II, and IV
II and IV
I, III, and IV
I and II
I and IV
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
Example Question #28 : Macromolecules
What factor determines whether humans are capable of digesting a polysaccharide?
The linkage between monomers
The branching pattern of the polysaccharide
The number of carbons in the carbohydrate
The number of monomers in the polysaccharide
The linkage between monomers
Carbohydrate monomers (monosaccharides) can be joined together with either alpha or beta linkages. Humans have the enzymes necessary in order to break down alpha linkages, but not beta linkages. Cellulose is a polysaccharide in which the monomers joined together by beta linkages, so humans cannot digest cellulose. Some bacterial species are capable of cleaving these linkages and have developed symbiotic or mutualistic relationships with animals. These bacterial species inhabit the mammalian digestive tract, cleaving beta linkages and gaining protection from the outside environment.
The size and branching pattern of a carbohydrate do not affect its ability to be digested.
Example Question #2 : Understanding Carbohydrates
Which polysaccharide is the primary form of energy storage in plants?
Peptidoglycan
Glycogen
Cellulose
Starch
Starch
The two most common polysaccharides found in plant cells are starch and cellulose. Starch is the primary source of energy storage, while cellulose is used to construct the plant's cell walls.
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