Organelles, Cytoplasmic

Cell organelle-cytoplasm Nuclear membrane-cytoplasm Endoplasmic reticulum-cytoplasm... 

The enzymes of the glyoxylate cycle in plants are contained in glyoxysomes, organelles devoted to this cycle. Yeast and algae carry out the glyoxylate cycle in the cytoplasm. The enzymes common to both the TCA and glyoxylate pathways exist as isozymes, with spatially and functionally distinct enzymes operating independently in the two cycles. 

MTs extend from the centrosome throughout the cytoplasm to the plasma membrane, where they are stabilized by caps. Sliding along the MTs, kinesin and dynein motors transport their cargoes between the center and the periphery of the cell. MTs present in the axons of neur ons are extended not only by addition of heterodimers to the plus ends but also by use of short MTs that initiate in the centrosome. Their axonal transport is mediated by dynein motors that are passively moved along actin filaments. Once formed in the axon, MTs serve as tracks for the fast axonal transport, i.e. the movement of membranous organelles and membrane proteins to the nerve ending. 

The cytoplasm of all eukaryotic cells contains a cytoskeletal framework that serves a multitude of dynamic functions exemplified by the control of cell shape, the internal positioning and movement of organelles, and the capacity of the cell to move and undergo division. 

Thus far, microtubules and actin filaments and their associated proteins have been discussed to advantage as independent cytoskeletal components. In actual fact, all of the components of the cytoskeleton (including intermediate filaments) are precisely integrated with one another (Langford, 1995), as well as with various cytoplasmic organelles, the nuclear membrane, the plasma membrane, and the extracellular matrix. In its totality the cytoskeleton subserves many coordinated and regulated functions in the cell ... 

The cytoskeleton is involved in the movement and positioning of cytoplasmic organelles (Cole and Lippincott-Schwartz, 1995). 

A three-dimensional meshwork of proteinaceous filaments of various sizes fills the space between the organelles of all eukaryotic cell types. This material is known collectively as the cytoskeleton, but despite the static property implied by this name, the cytoskeleton is plastic and dynamic. Not only must the cytoplasm move and modify its shape when a cell changes its position or shape, but the cytoskeleton itself causes these movements. In addition to motility, the cytoskeleton plays a role in metabolism. Several glycolytic enzymes are known to be associated with actin filaments, possibly to concentrate substrate and enzymes locally. Many mRNA species appear to be bound by filaments, especially in egg cells where they may be immobilized in distinct regions thereby becoming concentrated in defined tissues upon subsequent cell divisions. 

Targeting sequences on the protein are recognized in the cytoplasm or on the surface of the organelle. 

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