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The cell wall acts to protect the cell mechanically and chemically from its environment, and is an additional layer of protection to the cell membrane. Different types of cell have cell walls made up of different materials; plant cell walls are primarily made up of cellulose, fungi cell walls are made up of chitin and bacteria cell walls are ...
The centrosome is the main MTOC (microtubule organizing center) of the cell during mitosis. Each centrosome is made up of two cylinders called centrioles, oriented at right angles to each other. The centriole is formed from 9 main microtubules, each having two partial microtubules attached to it.
The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system to form an image of the environment, sight. Rods primarily mediate scotopic vision (dim conditions) whereas cones primarily mediate photopic vision (bright conditions), but the processes in each that supports phototransduction is ...
The name organelle comes from the idea that these structures are parts of cells, as organs are to the body, hence organelle, the suffix -elle being a diminutive. Organelles are either separately enclosed within their own lipid bilayers (also called membrane-bounded organelles) or are spatially distinct functional units without a surrounding ...
Compound eyes are made up of multiple small visual units, and are common on insects and crustaceans. Non-compound eyes have a single lens and focus light onto the retina to form a single image. This type of eye is common in mammals, including humans. The simplest eyes are pit eyes.
While the majority of cellular components are located within the cell itself, some may exist in extracellular areas of an organism. [5] Cellular components may also be called biological matter or biological material. Most biological matter has the characteristics of soft matter, being governed by relatively small energies. All known life is ...
Cellular compartments in cell biology comprise all of the closed parts within the cytosol of a eukaryotic cell, usually surrounded by a single or double lipid layer membrane. These compartments are often, but not always, defined as membrane-bound organelles. The formation of cellular compartments is called compartmentalization.
The thymus is made up of immature T cells called thymocytes, as well as lining cells called epithelial cells which help the thymocytes develop. T cells that successfully develop react appropriately with MHC immune receptors of the body (called positive selection) and not against proteins of the body (called negative selection). The thymus is ...