All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Question #6 : Cellular Processes
Which of the following is a common second messenger used in signal transduction pathways?
G subunits of G proteins
Receptor tyrosine kinases
Second messengers are the molecules in a signal transduction pathway that will activate an intracellular response. Epinephrine is a hormone that will bind a receptor on the exoplasmic face of the cell, making is a first messenger. G subunits interact with adaptor proteins that will then stimulate the production of second messengers. Receptor tyrosine kinases are examples of receptor proteins that will bind first messengers. cAMP, however, is a widely used second messenger that is involved in the activation of many pathways and signal amplification in the cytosol.
Example Question #2 : Signals, Communication, And Junctions
Which of the following signaling molecules does not elicit a second messenger response inside cells?
A second messenger response is created in cells that use signal transduction, meaning that the signaling molecules attach to a receptor on the outside of the cell. Steroid hormones are largely nonpolar, and can enter the cell in order to affect cellular processes at the level of transcription. As a result, they do not need to rely on second messenger pathways in order to elicit a response.