cell wall

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Related to primary wall: Primary cell wall

wall

 [wawl]
a structure bounding or limiting a space or a definitive mass of material; called also paries.
cell wall a rigid structure that lies just outside of and is joined to the plasma membrane of plant cells and most prokaryotic cells, which protects the cell and maintains its shape.
chest wall the structures bordering the thorax that move during breathing, including the rib cage, diaphragm, and abdomen.

cell wall

1. the outer layer or membrane of some animal and plant cells; in the latter, it is mainly cellulose.
2. in bacteria, the rigid structure, usually containing a peptidoglycan layer, that provides osmotic protection and defines bacterial shape and staining properties.

cell wall

n.
The rigid outermost cell layer found in plants and certain algae, bacteria, and fungi but absent from animal cells.

cell wall

the structure that covers and protects the plasma membrane in some kinds of cells, such as certain bacteria and all fungi and plant cells. The cell walls of plant cells are composed of cellulose.

cell wall

(sel wawl)
The outer layer or membrane of some animal and plant cells; in the latter, it is mainly cellulose.

cell wall

a thick, rigid coat formed outside the CELL MEMBRANE of plants, fungi and most bacteria. The cell wall is responsible for the shape of the organism and for protecting internal parts of the cell from damage. The plant cell wall is composed mainly of CELLULOSE secreted by the protoplasm of the cell. Structurally it consists of cellulose fibres embedded in a matrix of pectin and other polysaccharides, rather like fibreglass. Each fibre is built up from cellulose molecules which form strands called micelles. These are grouped into microfibrils, several hundred of which form a fibre. Older cells may also produce a secondary wall inside the primary wall which is thicker and contains LIGNIN for extra strength. Such cells often die after producing the secondary wall, e.g. XYLEM vessel cells.

The cell wall of BACTERIA is made of PEPTIDOGLYCAN, either alone or combined with other substances, and is used to differentiate the major types of bacteria: Gram-positive and Gram-negative (see GRAM'S STAIN). In Gram-positive bacteria, the wall generally consists of many layers of peptidoglycan, giving a very rigid structure. TEICHOIC ACIDS are also present. In Gram-negative bacteria there is a thin layer of peptidoglycan and an outer membrane. The peptidoglycan is attached to LIPOPROTEINS in the outer membrane. This membrane acts as a barrier to some ANTIBIOTICS, ENZYMES and so on; however, certain substances, such as nutrients, pass through. Part of the permeability of the membrane is due to PORINS. The ARCHAEA either lack cell walls or have unusual walls without peptidoglycan. In FUNGI a key component of most cell walls is CHITIN. The cell walls of YEASTS contain glucan and mannan. There may be additional layers, such as a CAPSULE, outside the cell wall.

cell wall

bimolecular lipid membrane that envelops the cell; contains receptors and pores through which small molecules can diffuse and larger molecules can be transported in and out of the cell

cell wall

(sel wawl)
1. Outer layer or membrane of some animal and plant cells.
2. In bacteria, the rigid structure that provides osmotic protection and defines bacterial shape and staining properties.

wall

a structure bounding or limiting a space or a definitive mass of material.

abdominal wall
see abdominal wall.
cell wall
a rigid structure that lies just outside of and is joined to the plasma membrane of plant cells and most prokaryotic cells, which protects the cell and maintains its shape.
wall chart
see calendar charts, shed sheet.
intestinal wall
composed of serosa, muscular tunic, the submucosa containing intestinal submucosal glands, and the mucosa of lining cells, goblet and enterochromaffin cells.
References in periodicals archive ?
The paucity of cellulosic fibrils in primary walls of lycopodiaceous tracheids contrasts with appearances found in ferns (Carlquist and Schneider, 2007), cycads (Schneider et al.
This may result in "scrape away" effects, in which various amounts of primary wall material are removed, depending on how deeply the blade edge cuts into any given pit membrane.
In the root perforation plate of Canna, no primary wall material is present in most of the perforations (Fig.
Narrow tracheary elements of Typha (Typhaceae) roots should be called tracheids because they retain a primary wall meshwork in the end wall pits (Fig.
8c) does not show such remnants: a result of the chemical removal of primary wall material by the acidic and oxidative qualities of the macerative fluid.
This suggests a relationship between tracheary element diameter and degree of end wall primary wall retention.
In most primary walls of monocot metaxylem, networks of primary wall cellulosic fibrils can be seen in preparations in which amorphous wall portions are sectioned away (e.
It the primary wall is not sectioned, thick strands running perpendicularly to the helical bars of secondary wall material are visible (Fig.
In the case of raw (untreated) material these groups are covered by non-cellulose compounds present in the primary wall of the natural fiber [ILLUSTRATION FOR FIGURE 7 OMITTED].
These sections have the advantage of withstanding the sectioning process better than thinner sections, and our observations with SEM confirmed that delicate primary walls sectioned well and were not damaged.
3, 7), pores may only partially perforate the pair of adherent primary walls between tracheids.
Although secondary wall architecture was not damaged by prolonged maceration, we believe that the integrity of primary walls was lost to various degrees by prolonged oxidative treatment.
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