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A cell wall is a structural layer that surrounds some cell types, found immediately outside the cell membrane.It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, and functions as a selective barrier. [1]
Each of the envelope membranes is a lipid bilayer that is between 6 and 8 nm thick. The lipid composition of the outer membrane has been found to be 48% phospholipids, 46% galactolipids and 7% sulfolipids, while the inner membrane has been found to contain 16% phospholipids, 79% galactolipids and 5% sulfolipids in spinach chloroplasts.
These chloroplasts are called muroplasts (from Latin "mura", meaning "wall"). Other chloroplasts were assumed to have lost the cyanobacterial wall, leaving an intermembrane space between the two chloroplast envelope membranes, [23] but has since been found also in moss, lycophytes and ferns. [127]
Parenchyma cells have a variety of functions: In leaves, they form two layers of mesophyll cells immediately beneath the epidermis of the leaf, that are responsible for photosynthesis and the exchange of gases. [2] These layers are called the palisade parenchyma and spongy mesophyll. Palisade parenchyma cells can be either cuboidal or elongated.
Chloroplasts: found in green algae (plants) and other organisms that derived their genomes from green algae. Muroplasts: also known as cyanoplasts or cyanelles, the plastids of glaucophyte algae are similar to plant chloroplasts, excepting they have a peptidoglycan cell wall that is similar to that of bacteria.
Cell nucleus: A cell's information center, the cell nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes , and is the place where almost all DNA replication and RNA synthesis ( transcription ) occur.
Cells come in a variety of different shapes. The cell wall may be smooth or ornamented with spines, granules, scrobiculations (pits), or pores. Cells are generally flattened. [6] Cells usually have one or two chloroplasts filling the cell; each chloroplast contains pyrenoids, typically one or two. [3]
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.