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In the Golgi apparatus, the proteins are glycosylated as needed and further posttranslational modifications, including cleavage and functionalization, may occur. The proteins are then moved into secretory vesicles which travel along the cytoskeleton to the edge of the cell. More modification can occur in the secretory vesicles (for example insulincarbon; green: oxygen; blue: nitrogen; pink: sulphur. The blue/purple ribbons denote the skeleton [-N-C-C-]n in the protein's amino acid sequence H-[-NH-CHR-CO-]n-OH where R is the part protruding from the skeleton in each amino acid. Insulin ( Latin insu is cleaved from proinsulin in the secretory vesicles).
Eventually, the vesicle fuses with the cell membraneA component of every biological cell, the cell membrane (or plasma membrane is a thin and structured bilayer of phospholipid and protein molecules that encapsulate the cell. It separates a cell's interior from its surroundings and controls what moves in a in a process called exocytosisExocytosis is the process of a biological cell releasing substances into the extracellular fluid (its environment). Exocytosis is the opposite of endocytosis. Vesicles that contain the substances to be released are transported to the plasma membrane and f, dumping its contents into the cell's environment.
Strict biochemical control is maintained over this sequence by usage of a pHAlternate uses: see Ph pH (potential (of) hydrogen) is a measure of the concentration of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. The concept was introduced by S. Sorensen in 1909. The p stands for the German potenz mean gradient: the pH of the cytosol is 7.4, the ER's pH is 7.0, and the cis-golgi has a pH of 6.5. Secretory vesicles have pHs ranging between 5.0 and 6.0; some secretory vesicles evolove into lysosomeLysosomes are organelles in eukaryotic cells that contain digestive enzymes to digest macromolecules. They are built in the Golgi apparatus. 8, the interior of the lysosomes is more acidic than the cytosol (pH 7). The lysosome single membrane stabilizes ts, which have a pH of 4.8.