All living things are composed of cells, but cells are complex organisms themselves. Every cell, whether it's part of a greater organism or a simple amoeba on its own, requires certain biological processes to function. One of the most important of these processes is cytoplasmic streaming – also referred to as cyclosis, or cytoplasmic movement. Though the process as a whole isn't fully understood, cytoplasmic streaming is what allows nutrients and proteins to move about inside a cell. In certain single-celled organisms, it also gives the cell the ability to move.
TL;DR (Too Long; Didn't Read)
TL;DR (Too Long; Didn't Read)
Cytoplasmic streaming, commonly referred to as cyclosis, is the process by which the fluid cytoplasm inside a given cell is moved around in currents, carrying nutrients, proteins, and organelles through the cell – and allowing certain simple single-celled organisms to move. The mechanism as a whole isn't completely understood, but the going theory is that cyclosis is powered by a network of 'motor protein' fibers positioned just inside the cell's membrane.
Movement Inside Cells
All cells – whether they be animal cells, plant cells, fungal cells, or single-celled organisms like amoeba or protozoa – contain a number of components crucial to that cell's continued function: Organelles process nutrients, ensure healthy cell division and keep the cell "programmed" to complete its intended function inside a body or other environment. But these components aren't fixed to specific points inside the cell, like a human's organs are. They float around inside the cell along what appears to be a circular current, and when nutrients are taken into a cell, or something is processed or produced within a cell to be sent elsewhere, those nutrients are carried to the appropriate place. All of this is done through cytoplasmic streaming. However, despite its importance, scientists don't fully understand how it occurs. This is frustrating, given that cyclosis is what allows simpler single-celled organisms to move when they don't possess cilia or flagella.
The current running theory is that cyclosis occurs as a direct result of what are called "motor proteins." These fibers, made up of myosin and actin, are positioned just inside the cell membrane. By using ATP produced inside the cell as fuel, these protein fibers, either through self-organization or some predetermined process, move cytoplasm and the organelles or nutrients suspended in it through the cell. It has also been suggested in the past that the process of cell division could create a current within the cytoplasm, perhaps in conjunction with motor proteins – but this idea has fallen out of favor.
- Encyclopaedia Britannica: Cytoplasmic Streaming
- Valencia College Botany: The Cell
- University of Arizona Biology: Cytoskeleton Tutorial
- Woodhouse, F. G. and Goldstein, R. E.; Cytoplasmic Streaming in Plant Cells Emerges Naturally by Microfilament Self-Organization; PNAS; 2013
- Goldstein, R. E. and van de Meent, J-W; A Physical Perspective on Cytoplasmic Streaming; Interface Focus; 2015
- Shimmen, T. and Yokota, E.; Cytoplasmic Streaming in Plants; Current Opinion in Cell Biology; 2004