Supported by. Pat Tillman walked away from a lucrative career in the National Football League to join the military and fight in Afghanistan, where he was ultimately killed by friendly fire in an incident that was initially covered up.
A membrane-enclosed sac that is part of the endomembrane system of a eukaryotic cell, having diverse functions. central vacuole. A membrane-enclosed sac occupying most of the interior of a mature plant cell, having diverse roles in reproduction, growth, and development. peroxisome. sac made of membrane in the cytoplasm of a eukaryotic cell. endoplasmic reticulum (ER). An extensive membranous network in a eukaryotic cell, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.
Many plant cells have a large, single central vacuole that typically takes up most of the room in the cell (80 percent or more). Vacuoles in animal cells, however, tend to be much smaller, and are more commonly used to temporarily store materials or to transport substances. The central vacuole in plant cells (see Figure 1) is enclosed by a membrane termed the tonoplast, an important and highly integrated component of the plant internal membrane network (endomembrane) system.