Practice question

Physiology of carbon dioxide delivery relies on chloride bicarbonate exchange across erythrocyte membrane rather than G protein signaling. Authentic transporter Band 3 anion exchanger 1 SLC4A1 abundant integral protein fourteen transmembrane helices catalyzing electroneutral one to one antiport of chloride for bicarbonate at high turnover supporting conversion of CO2 to bicarbonate via carbonic anhydrase for plasma carriage known as chloride shift Hamburger phenomenon. At pulmonary capillaries exchange reverses enabling CO2 exhalation. GPCR family members are seven-transmembrane receptors coupling to heterotrimeric G proteins generating second messengers cAMP inositol trisphosphate diacylglycerol activating kinases but not transporting chloride as primary mode. Glycophorin major single-pass sialoglycoprotein provides glycocalyx negative charge and pathogen receptor lacking transport activity, spectrin filamentous tetrameric cytoskeletal protein maintains biconcave elasticity lacking ion translocation. Therefore scientifically validated chloride transporter is Band 3 although answer choice listed as GPCR in this dataset reflects probable curation inconsistency noted here, emphasizing need to recognize Band 3 as genuine chloride shift mediator for acid base and gas transport physiology.