Cytoplasmic streaming is also known cyclosis. It is a process by which things within the cell's cytoplasm, such as nutrients, waste, and organelles, can be transported to other areas of the cell. Cytoplasmic streaming can be triggered by a variety of cellular signals, including hormones and increased energetic demands. Cytoplasmic streaming is just one way in which a cell is able to survive in a dynamic and rapidly changing environment.
One process that can cause cytoplasmic streaming is cell division. When a cell divides, it needs to also move around its organelles to ensure that the newly created cells have the organelles necessary to survive. These organelles are ones such as ribosomes, which are needed to make proteins, mitochondria, which are needed for energy production, and golgi apparatus, which is necessary for protein excretion.
Cytoplasmic streaming is also used by plant cells to move chloroplasts. Chloroplasts are what allow plants to absorb sunlight and use the light energy to make sugars and other sources of energy. Plant cells use cytoplasmic streaming to rotate chloroplasts through areas of the cell that are receiving the most sunlight, thus making sure that the chloroplasts are being used as efficiently as possible.
Some unicellular organisms, such as amoebas, use cytoplasmic streaming as a way of movement. By moving organelles around within the cytoplasm, these animals are able to change their shape, which allows them to move toward nutrients or away from toxins.
Cytoplasmic streaming occurs via the use of the cell's cytoskeleton. The cytoskeleton is a network of fibers and tubes that connect the cell, giving it support and structure. Cytoplasmic streaming involves the contraction of a type of fiber called microfilaments. Microfilaments are made up of a protein called actin and when the cell needs to move an organelle, it attaches a microfilament to it and then pulls on the microfilament to cause the organelle to move within the cytoplasm.
A variety of proteins, called motor proteins, are responsible for causing microfilament contraction. These include the family of proteins known as myosins, as will as other proteins such as kinesin and dynamin. These proteins use energy, stored in the form of a molecule called ATP, to bend and pull the microfilaments, which allows for organelle movement.
