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Gas vacuoles are membrane-bound, spindle-shaped vesicles, found in some planktonic bacteria and Cyanobacteria, that provides buoyancy to these cells by decreasing their overall cell density. Positive buoyancy is needed to keep the cells in the upper reaches of the water column, so that they can continue to perform photosynthesis.
The aromatic/arginine or "ar/R" selectivity filter is a cluster of amino acids that help bind to water molecules and exclude other molecules that may try to enter the pore. It is the mechanism by which the aquaporin is able to selectively bind water molecules and so to allow them through, and to prevent other molecules from entering.
The function and significance of vacuoles varies greatly according to the type of cell in which they are present, having much greater prominence in the cells of plants, fungi and certain protists than those of animals and bacteria. In general, the functions of the vacuole include: Isolating materials that might be harmful or a threat to the cell
A fimbria (plural fimbriae also known as a pilus, plural pili) is a short, thin, hair-like filament found on the surface of bacteria. Fimbriae are formed of a protein called pilin and are responsible for the attachment of bacteria to specific receptors on human cells (cell adhesion).
In gram-negative bacteria, the inner membrane is the major permeability barrier. [10] The outer membrane is more permeable to hydrophilic substances, due to the presence of porins. [5] Porins have threshold sizes of transportable molecules that depend on the type of bacteria and porin.
The stage in which water flows into the CV is called diastole. The contraction of the contractile vacuole and the expulsion of water out of the cell is called systole. Water always flows first from outside the cell into the cytoplasm, and is only then moved from the cytoplasm into the contractile vacuole for expulsion. Species that possess a ...
DNA and RNA are made from “right-handed” molecules while proteins are made from “left-handed” amino acids. This chirality or handedness of life molecules dictates their chemical reactivity ...
The proportion of cell volume that is cytosol varies: for example while this compartment forms the bulk of cell structure in bacteria, [9] in plant cells the main compartment is the large central vacuole. [10] The cytosol consists mostly of water, dissolved ions, small molecules, and large water-soluble molecules (such as proteins).