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The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles [1] and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell and contained within the nuclear membrane is termed the nucleoplasm .
In many animal cells, centrioles and spindles keep nuclei centered within a cell for mitotic, meiotic, and other processes. Without such a centering mechanism, disease and death can result. While mouse oocytes do have centrioles, they play no role in nucleus positioning, yet, the nucleus of the oocyte maintains a central position.
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 ...
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
Some animals like the fruit fly do not have any cytoplasmic intermediate filaments. In those animals that express cytoplasmic intermediate filaments, these are tissue specific. [ 5 ] Keratin intermediate filaments in epithelial cells provide protection for different mechanical stresses the skin may endure.
[4] [5] Such a soluble cell extract is not identical to the soluble part of the cell cytoplasm and is usually called a cytoplasmic fraction. [6] The term cytosol is now used to refer to the liquid phase of the cytoplasm in an intact cell. [6] This excludes any part of the cytoplasm that is contained within organelles. [7]
Flagella may have hairs (mastigonemes), as in many stramenopiles. Their interior is continuous with the cell's cytoplasm. [42] [43] Centrioles are often present, even in cells and groups that do not have flagella, but conifers and flowering plants have neither. They generally occur in groups that give rise to various microtubular roots.
When juvenile zebrafish are growing, skin cells must quickly cover the rapidly increasing surface area of the zebrafish. These skin cells divide without duplicating their DNA (the S phase of mitosis) causing up to 50% of the cells to have a reduced genome size. These cells are later replaced by cells with a standard amount of DNA.