Cytosol
Cytosol is the aqueous component of the cytoplasm in cells, primarily composed of water and a complex mixture of chemicals that play crucial roles in cell metabolism. It comprises more than 40% of the volume of plant cells and has a gelatinous consistency due to the high concentration of dissolved substances. Organized around a cytoskeleton framework of fibrous molecules and protein filaments, the cytosol facilitates essential cellular functions, including energy transformations necessary for growth, repair, and reproduction.
In cytosol, vital processes such as glycolysis, the initial step of cellular respiration, occur, aiding in the production and distribution of energy within the cell. It also serves as a medium for the synthesis, sorting, and transport of proteins, with ribosomes in the cytosol being responsible for protein production. Messenger RNA (mRNA) is transported through the cytosol to ribosomes, directing protein synthesis. Additionally, cytosol plays a critical role in nutrient acquisition, waste removal, and the movement of ions to support organelle function, underscoring its importance in maintaining cellular health and activity.
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Subject Terms
Cytosol
Categories: Anatomy; cellular biology
The cytosol is organized around a framework of fibrous molecules and protein filaments that constitute the cytoskeleton. Although the cytosol consists mostly of water, it contains many chemicals that control cell metabolism, including signal transmission and reception, cellular respiration, and protein transcription factors. The cytosol makes up more than 40 percent of the plant cell volume and contains thousands of different kinds of molecules that are involved in cellular biosynthesis. Because cytosol has so much material dissolved in it, it has a gelatinous consistency.
Function
The cytosol provides locations in the cell where chemical activities and energy transformations responsible for growth, repair, and reproduction can occur. Through diffusion and active transport, cytosol collects many essential nutrients from its surroundings, including carbon, hydrogen, oxygen, potassium, nitrogen, phosphorus, and a variety of micronutrients. The constant motion of the cytosol provides a mechanism for moving and supplying these vital nutrients by ionic transport to the organelles so that they can perform their specific jobs.
Cytosol also assists with the removal of unwanted waste products from the cell. Glycolysis, the initial step in cellular respiration, occurs in the cytosol. In cellular energy transactions, the cytosol helps distribute useful energy and dissipate the associated heat.
Cytosol plays a key role in the vital processes of protein production, sorting, and transportation. All plant proteins are synthesized by ribosomes in the cytosol. Cytosol provides the medium that assists in the transporting of messenger ribonucleic acid (mRNA) to ribosomes, where they synthesize proteins. The first portion of the amino acid sequence of a protein contains a signal sequence that is checked by proteins in the cytosol. Signal sequences are like street addresses that tell where the growing protein is to be transported. Some signal sequences direct a ribosome to the endoplasmic reticulum (ER), where the protein sequence is completed, is stored in the ER’s lumen (the space inside the ER), and is eventually transported in a vesicle to another organelle or is exported through the cytosol out of the cell. Proteins lacking a signal sequence are completed by the ribosome and released into the cytosol.
Bibliography
Gunning, Brian E. S., and Martin W. Steer. Plant Cell Biology: Structure and Function. Boston: Jones and Bartlett, 1996. Comprehensive overview of plant cells. Includes illustrations, index.
Salisbury, Frank B., and Cleon W. Ross. Plant Physiology. 4th ed. Pacific Grove, Calif.: Brooks/Cole, 1999. A fundamental textbook that covers plant cell biology as well as molecular biology and genetics. Includes illustrations, bibliographical references, and index.
Stern, Kingsley Rowland. Introductory Plant Biology. 8th ed. Boston: McGraw-Hill, 1999. Introductory botany text discusses all the basic concepts of plants. Includes color photos, glossary, bibliographical references, and index.