Practice question

Plants lack animal Na+/K+ gradient but generate proton motive force via plasma membrane P-type H+-ATPase and vacuolar V-type H+-ATPase and pyrophosphatase, driving uptake and compartmentalization of metabolites. Detoxification of xenobiotics, herbicides, and endogenous secondary metabolites employs ATP-binding cassette transporters localized predominantly in vacuolar membrane tonoplast and plasma membrane. Vacuolar ABCC members often called MRP-like transport glutathione S-conjugates, phytochelatin heavy metal complexes, and glucuronide conjugates into vacuole for sequestration, reducing cytosolic toxicity. Plasma membrane ABCG members extrude antimicrobial terpenoids and cuticular lipids. In Arabidopsis, AtABCC1 and AtABCC2 are classic vacuolar transporters conferring tolerance to arsenic and cadmium phytochelatin complexes. Tonoplast localization enables long-term storage away from sensitive metabolic processes, paralleling hepatic canalicular ABC exporters. Exclusive peroxisomal or endoplasmic reticulum residence is not typical for xenobiotic detoxification ABC pumps; tonoplast and plasma membrane are major detox sites contributing to environmental adaptation. Such detailed mechanistic insight is frequently examined in competitive tests including NEET, CUET, CSIR-NET and GATE where transporter classification, energetics and disease linkage are integrated into problem-solving questions.