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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.
The endomembrane system is composed of the different membranes (endomembranes) that are suspended in the cytoplasm within a eukaryotic cell. These membranes divide the cell into functional and structural compartments, or organelles. In eukaryotes the organelles of the endomembrane system include: the nuclear membrane, the endoplasmic reticulum ...
The TOC complex, or translocon on the outer chloroplast membrane, is a collection of proteins that imports preproteins across the outer chloroplast envelope. Five subunits of the TOC complex have been identified—two GTP-binding proteins Toc34 and Toc159, the protein import tunnel Toc75, plus the proteins Toc64 [43] and Toc12. [46]
Nuclear envelope. The nuclear envelope, also known as the nuclear membrane, [1][a] is made up of two lipid bilayer membranes that in eukaryotic cells surround the nucleus, which encloses the genetic material. The nuclear envelope consists of two lipid bilayer membranes: an inner nuclear membrane and an outer nuclear membrane. [4]
The inner chloroplast membrane borders the stroma and regulates passage of materials in and out of the chloroplast. After passing through the TOC complex in the outer chloroplast membrane, polypeptides must pass through the TIC complex (translocon on the inner chloroplast membrane) which is located in the inner chloroplast membrane. [91]
Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as grana (singular: granum).
The membrane of the rough endoplasmic reticulum is in the form of large double-membrane sheets that are located near, and continuous with, the outer layer of the nuclear envelope. [12] The double membrane sheets are stacked and connected through several right- or left-handed helical ramps, the "Terasaki ramps", giving rise to a structure ...
The barber pole chloroplast motion resulting from cytoplasmic streaming has one flow upward and another downward. [8] The downward motion of the chloroplasts moves a bit faster than the upward flow producing a ratio of speeds of 1.1. [8] [15] This ratio is known as the polar ratio and depends on the force of gravity. [15]