It’s C. The start point of the cycle. I took this on my test
Chemoreceptors is the answer
A protein kinase that is specific to the amino acids serine and threonine is known as a mitogen-activated protein kinase (MAPK or MAP kinase; also known as a serine/threonine-specific protein kinase).
<h3>Mitogen-activated protein kinase :</h3>
A small number of cell surface receptors can ultimately generate a large intracellular response due to activation of kinase cascades.
In order to trigger an appropriate physiological response, such as cellular proliferation, differentiation, development, inflammatory reactions, and death in mammalian cells, MAPK pathways relay, amplify, and integrate information from a variety of stimuli.
Tyrosine phosphorylation, specifically numerous tyrosines on each RTK in the dimer, is how cross-linking triggers the tyrosine kinase activity in these RTKs. The term "cross-phosphorylation" refers to this action.
The activation of a MAPKKKK or MAPKKK by stimulation of plasma membrane receptors is the initial stage of signal transduction. The MAPKKK then phosphorylates two serine or threonine residues in the S/T-X5-S/T (X is any amino acid) motif of its activation loop, activating a downstream MAPKK.
Learn more about MAPK here:
brainly.com/question/23449262
SPJ4
