GRE Subject Test: Biology : Understanding Receptors
Study concepts, example questions & explanations for GRE Subject Test: Biology
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Example Questions
Example Question #13 : Proteins
When presented with its ligand, glutamate, a metabotropic glutamate receptor (mGluR) can do any of the following except __________.
modulate transcription factor activation
change conformation to go from inactive to active
trigger an increase in intracellular calcium ion concentration
activate the pathway that results in PKC activation
open to permit passage of sodium ions through the channel pore
open to permit passage of sodium ions through the channel pore
The key here is knowing that metabotropic receptors are NOT ion channels. They exert their effects through downstream signaling cascades. Ions cannot travel through a metabotropic receptor.
All other answers are potential outcomes of activating an mGluR.
Example Question #1 : Understanding Receptors
Once a G-protein coupled receptor (GPCR) has bound to its ligand, which of the following steps allows the 
Exchanging the G-protein's bound GDP for a GTP
Exchanging the G-protein's bound ADP for an ATP
Degradation of the GPCR's C-terminal tail that is bound to the 
None of these
Exchanging the G-protein's association with a magnesium ion for a calcium ion
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?
Recruitment of natural killer cells
Recognition of pathogen-associated molecular patterns (PAMPs)
Recognition and dimerization of integrins
Recruitment of macrophages
Recognition of coagulation factors (platelet clotting factors)
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?
Close range cell signaling
Intracellular signaling
Same cell signaling
Cell signaling across a synapse
Long 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.
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