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A granum (plural grana) is a stack of thylakoid discs. Chloroplasts can have from 10 to 100 grana. Grana are connected by stroma thylakoids, also called intergranal thylakoids or lamellae. Grana thylakoids and stroma thylakoids can be distinguished by their different protein composition.
Stroma, in botany, refers to the colorless fluid surrounding the grana within the chloroplast. [ 1 ] Within the stroma are grana (stacks of thylakoid ), the sub-organelles where photosynthesis is started [ 2 ] before the chemical changes are completed in the stroma.
Within the envelope membranes, in the region called the stroma, there is a system of interconnecting flattened membrane compartments, called the thylakoids. The thylakoid membrane is quite similar in lipid composition to the inner envelope membrane, containing 78% galactolipids, 15.5% phospholipids and 6.5% sulfolipids in spinach chloroplasts. [3]
All green parts of a plant contain chloroplasts as the color comes from the chlorophyll. [11] The plant cells which contain chloroplasts are usually parenchyma cells, though chloroplasts can also be found in collenchyma tissue. [185] A plant cell which contains chloroplasts is known as a chlorenchyma cell.
The basic unit of the membrane system is a flattened single vesicle called the thylakoid; thylakoids stack into grana. All the thylakoids of a granum are connected with each other, and the grana are connected by intergranal lamellae. [4] It is placed between the two primary cell walls of two plant cells and made up of intracellular matrix.
Components of a typical chloroplast. 1 Granum 2 Chloroplast envelope. 2.1 Outer membrane 2.2 Intermembrane space 2.3 Inner membrane. 3 Thylakoid. 3.1 Thylakoid space 3.2 Thylakoid membrane. 4 Stromal thylakoid 5 Stroma 6 Nucleoid (DNA ring) 7 Ribosome 8 Plastoglobulus 9 Starch granule
For example, chloroplasts in plants and green algae have lost all phycobilisomes, the light harvesting complexes found in cyanobacteria, red algae and glaucophytes, but instead contain stroma and grana thylakoids. The glaucocystophycean plastid—in contrast to chloroplasts and rhodoplasts—is still surrounded by the remains of the ...
This creates a H + gradient, making H + ions flow back into the stroma of the chloroplast, providing the energy for the (re)generation of ATP. [citation needed] The photosystem II complex replaced its lost electrons from H 2 O, so electrons are not returned to photosystem II as they would in the analogous cyclic pathway. Instead, they are ...