Practice question

In animal cells Golgi modifies proteins, but plant cells possess additional requirement to produce noncellulosic cell wall polysaccharides that constitute matrix embedding cellulose microfibrils. Golgi stacks, often four hundred per cell moving along actin tracks, synthesize pectins homogalacturonan methylesterified in cis medial then de-esterified and calcium crosslinked in trans and at wall, rhamnogalacturonan I II highly branched, and hemicelluloses xyloglucan backbone synthesized by CSLC glucan synthases, xylan, arabinan, galactan sidechains added by glycosyltransferases GT47, GT8 families. Nucleotide sugars UDP-galacturonic acid imported by transporters from cytosol where converted from glucose. Trans Golgi network vesicles fuse with phragmoplast cell plate during cytokinesis depositing wall material, also delivering cellulose synthase complexes to plasma membrane via secretory vesicles. ATP production confined to mitochondria chloroplasts, protein degradation vacuole, DNA replication nucleus. Mutants deficient in Golgi enzymes show dwarfism, altered extensibility, confirming central participation in wall biogenesis supporting turgor pressure and growth. Integration with cell cycle kinases, calcium signaling and mechanical cues ensures coordinated remodeling during growth, migration and differentiation.