Unlike steroid hormones, signaling molecules that are large and/or hydrophilic cannot pass through the cell's plasma membrane and therefore must bind extracellularly to receptor molecules in the plasma membrane. Two types of signal receptors embedded in the cell's plasma membrane are G protein-coupled receptors and receptor tyrosine kinases. Classify each phrase by whether it applies to G protein-coupled receptors only, receptor tyrosine kinases only, both receptors, or neither receptor.
G-protein: interact directly with G proteins
Receptor tryosine kinases: catalyzes the transfer of a phosphate group t o the receptor, binding of the signaling molecule forms a dimer
Both: binding site for signaling molecule is located on the extracellular side of cell, receptor is locate in plasma membrane
Neither: binding of the signaling molecule allows ions to flow through a channel in the receptor

Both G protein-coupled receptors and receptor tyrosine kinases are transmembrane receptors that have a binding domain located on the extracellular side of the plasma membrane. The binding of a signaling molecule to these receptors is the first step in a signaling pathway. However, what happens after a signaling molecule binds is different for each receptor.
An activated G protein-coupled receptor activates a G protein inside the cell, which involves the release of GDP and the binding of GTP. The activated G protein then activates an associated enzyme, leading to a cellular response.
Receptor tyrosine kinases form dimers after binding signaling molecules. The tyrosines are then phosphorylated, fully activating the receptor. Each phosphorylated tyrosine can bind a relay protein, each of which can trigger a transduction pathway. In this way, a single signaling-molecule binding event can trigger multiple signal transduction pathways and thus multiple cellular responses.