G protein‑coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) are two basic receptor types by which cells transduce signals.
A) Classify each statement as describing GPCRs, RTKs, both types of receptors, or neither of these two types.
1. phosphorylation of receptor can terminate signal or desensitize receptor.
2. autophosphorylation of receptor can initiate signal.
3. structure contains seven transmembrane helices.
4. an example is the insulin receptor.
5. an example is the epinephrine receptor.
6. activate heterotrimeric G proteins directly.

GPCRs,RTKs

Explanation:

G Protein Coupled Receptors(GPCRs) are more common and found in almost all eukaryotes whereas Receptor Tyrosine Kinases(RTKs) are second largest family of receptors that relay signal from cell surface to the interior

G protein coupled receptors(GPCRs) interacts with the ligand activated GPCR and phosphorylates its intracellular domain.This process of phosphorylation can terminate signal or desensitize of receptor can initiate signal in case of Receptor Tyrosine Kinases(RTKs);Autophosphorylation is a feature of RTKs in which receptor dimerization activates intrinsic tyrosine kinase activity by which they phosphorylate its own tyrosine residue on cytosolic phaseSeven transmembrane helices can be seen in case of G protein-coupled receptors(GPCRs);transmembrane protein of it consists of single polypeptide and spans the membrane 7 timesInsulin receptor is a part of Insulin Signalling which comes under RTKs;Insulin receptor always exist in case of dimeric formEpinephrine receptor is an example of GPCRs;Epinephrine is an endocrine hormones produced in stress conditionTransmembrane protein of GPCR activates G protein,activated G protein binds with effector enzyme and activate it;effector enzyme further can produce or destroy secondary messenger