Also called G protein-coupled receptor, seven-transmembrane domain receptor, 7 TM receptor, constitute a large protein family of receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses.
They pass through the cell membrane 7 times.

G-protein-Linked receptors are a huge family that have hundreds of members identified.
Ion-channel-linked receptors (e.g. GABAB, NMDA, etc.)
are only a part of them.

Table 1.
Three major families of Trimeric G Proteins
Also called G protein-coupled receptor, seven-transmembrane domain receptor, 7 TM receptor, constitute a large protein family of receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses. They pass through the cell membrane 7 times. 
G-protein-Linked receptors are a huge family that have hundreds of members identified. Ion-channel-linked receptors (e.g. GABAB, NMDA, etc.) are only a part of them.
Table 1. Three major families of Trimeric G Proteins
Ligand-gated ion channel