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This organelle is necessary because freshwater has a lower concentration of solutes (such as salt) than the amoeba's own internal fluids . Because the surrounding water is hypotonic with respect to the contents of the cell, water is transferred across the amoeba's cell membrane by osmosis. Without a contractile vacuole, the cell would fill with ...
Food enveloped by the Amoeba is stored in digestive organelles called food vacuoles. Amoeba, like other unicellular eukaryotic organisms, reproduces asexually by mitosis and cytokinesis. Sexual phenomena have not been directly observed in Amoeba, although sexual exchange of genetic material is known to occur in other Amoebozoan groups. [15]
Amoeba proteus is a large species of amoeba closely related to another genus of giant amoebae, Chaos. As such, the species is sometimes given the alternative scientific name Chaos diffluens. [1] [2] Amoeba proteus in locomotion. This protozoan uses extensions called pseudopodia to move and to eat smaller unicellular organisms.
Shown is a micrograph of an amoeba; the darker pink nucleus is central to the eukaryotic cell, with the majority of the rest of the cell's body belonging to the endoplasm. Though not visible, the ectoplasm resides directly internal to the plasma membrane. Endoplasm generally refers to the inner (often granulated), dense part of a cell's cytoplasm.
Inside the amoeba, there are proteins that can be activated to convert the gel into the more liquid sol state. Cytoplasm consist largely of actin and actin is regulated by actin-binding protein . Actin binding proteins are in turn regulated by calcium ions; hence, calcium ions are very important in the sol-gel conversion process.
They are simpler and smaller than eukaryotic cells, and lack a nucleus, and other membrane-bound organelles. The DNA of a prokaryotic cell consists of a single circular chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid. Most prokaryotes are the smallest of all organisms, ranging ...
The nucleus is an organelle that houses the DNA that makes up a cell's genome. DNA (Deoxyribonucleic acid) itself is arranged in complex chromosomes. [58] Mitochondria are organelles vital in metabolism as they are the site of the citric acid cycle and oxidative phosphorylation. They evolved from symbiotic bacteria and retain a remnant genome. [59]
It senses extracellular signalling molecules, chemoattractants (e.g. cAMP for Dictyostelium cells), [7] to extend pseudopodia at the membrane area facing the source of these molecules. The chemoattractants bind to G protein-coupled receptors, which activate GTPases of the Rho family (e.g. Cdc42, Rac) via G proteins.