Cell sap is the liquid contained within a plant cell vacuole. The chemical composition of this liquid differs significantly from the materials contained outside the vacuole in the surrounding cytosol. This difference aids in the transfer of materials across the vacuole's membrane, called the tonoplast.Continue Reading
The vacuole and the cell sap inside it perform a variety of vital functions, such as storing nutrients and mineral salts, sequestering and isolating toxic metabolites, enabling waste disposal and providing structural support. Because of their relatively large size in plant cells, the vacuoles can take up as much as 30 to 80 percent of the cell's volume. The ability of the liquid-filled vacuole to maintain turgor pressure against the cell's outer wall is what enables it to help support structures such as flowers and leaves. When plants do not obtain sufficient water, the turgor pressure exerted by the vacuoles drops and the plant wilts.
Cell sap may contain pigments that account for a flower's recognizable colors. The cell sap may also contain enzymes that will react with other enzymes in the outside cytosol if the vacuole's membrane is broken. The new chemicals produced by the reaction between enzymes can be toxic to certain animals and represent a protective device that encourages herbivores to move on to another food source. The release of the enzyme syn-propanethial-S-oxide from cut onions is one example. In garlic plants, the combination of the enzymes alliin and alliinase will react to form allicin when a vacuole is broken.Learn more about Cells
Cell theory was developed in the early 19th century by three German scientists, Theodor Schwann, Matthias Jacob Schleiden and Rudolf Virchow. While all three scientists contributed to the generally accepted classical cell theory, each hypothesized different sections of it and had parts of their theory refuted and replaced.Full Answer >
Cell division is limited by a process called cellular senescence, during which cells in culture divide more slowly before stopping entirely. The cells do not necessarily die during senescence, but they no longer replicate.Full Answer >
Cell division is part of the cell cycle, and it is caused either by binary fission or as part of a multiple-phase cycle. Binary fission is the method by which prokaryotic cells divide. Eukaryotic cells use the three-phase cycle commonly referred to as mitosis.Full Answer >
Cell membranes are generally composed of proteins and fatty-acid-based lipids, according to the Encyclopedia Britannica. Membranes actively involved in metabolism have a higher proportion of protein. Mitochondria, the cell’s fastest metabolizing organelles, have a membrane that consists of 75 percent protein. The Schwann cell’s membrane only has 20 percent protein.Full Answer >