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Non-cellular life, also known as acellular life, is life that exists without a cellular structure for at least part of its life cycle. [1] Historically, most definitions of life postulated that an organism must be composed of one or more cells, [2] but, for some, this is no longer considered necessary, and modern criteria allow for forms of life based on other structural arrangements.
Protoplast (from Ancient Greek πρωτόπλαστος (prōtóplastos) 'first-formed'), is a biological term coined by Hanstein in 1880 to refer to the entire cell, excluding the cell wall. [ 1 ] [ 2 ] Protoplasts can be generated by stripping the cell wall from plant , [ 3 ] bacterial , [ 4 ] [ 5 ] or fungal cells [ 5 ] [ 6 ] by mechanical ...
The secondary cell wall, a thick layer formed inside the primary cell wall after the cell is fully grown. It is not found in all cell types. It is not found in all cell types. Some cells, such as the conducting cells in xylem , possess a secondary wall containing lignin , which strengthens and waterproofs the wall.
The cells of plants, algae, fungi and most chromalveolates, but not animals, are surrounded by a cell wall. This is a layer outside the cell membrane, providing the cell with structural support, protection, and a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell. [45] The major polysaccharides making up ...
In animals, the plasma membrane is the outer boundary of the cell, while in plants and prokaryotes it is usually covered by a cell wall. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of phospholipids , which are amphiphilic (partly hydrophobic and partly hydrophilic ).
Light micrograph of a moss's leaf cells at 400X magnification. The following outline is provided as an overview of and topical guide to cell biology: . Cell biology – A branch of biology that includes study of cells regarding their physiological properties, structure, and function; the organelles they contain; interactions with their environment; and their life cycle, division, and death.
Protoplasm (/ ˈ p r oʊ t ə ˌ p l æ z əm /; [1] [2] pl. protoplasms) [3] is the part of a cell that is surrounded by a plasma membrane.It is a mixture of small molecules such as ions, monosaccharides, amino acids, and macromolecules such as proteins, polysaccharides, lipids, etc.
This crystallization process is no longer accepted with modern cell theory. In 1839, Theodor Schwann states that along with plants, animals are composed of cells or the product of cells in their structures. [11] This was a major advance in the field of biology since little was known about animal structure up to this point compared to plants ...