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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. [3] Photosynthesis occurs in two stages.
The thylakoid membranes of higher plants are composed primarily of phospholipids [5] and galactolipids that are asymmetrically arranged along and across the membranes. [6] Thylakoid membranes are richer in galactolipids rather than phospholipids; also they predominantly consist of hexagonal phase II forming monogalacotosyl diglyceride lipid.
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]
In general outline, photosynthesis is the opposite of cellular respiration: while photosynthesis is a process of reduction of carbon dioxide to carbohydrates, cellular respiration is the oxidation of carbohydrates or other nutrients to carbon dioxide. Nutrients used in cellular respiration include carbohydrates, amino acids and fatty acids.
2 + 6 NADPH + 9 ATP + 5 H 2 O → glyceraldehyde-3-phosphate (G3P) + 6 NADP + + 9 ADP + 8 P i (P i = inorganic phosphate) Hexose (six-carbon) sugars are not products of the Calvin cycle. Although many texts list a product of photosynthesis as C 6 H 12 O 6, this is mainly for convenience to match the equation of aerobic respiration, where six ...
A proton gradient is created across the thylakoid membrane (6) as protons (3) are transported from the chloroplast stroma (4) to the thylakoid lumen (5). Through chemiosmosis, ATP (9) is produced where ATP synthase (1) binds an inorganic phosphate group (8) to an ADP molecule (7).
The optimal stroma pH for the Calvin cycle is 8.1, with the reaction nearly stopping when the pH falls below 7.3. [172] CO 2 in water can form carbonic acid, which can disturb the pH of isolated chloroplasts, interfering with photosynthesis, even though CO 2 is used in photosynthesis.
5 cluster (including two chloride ions), one non heme Fe 2+ and two putative Ca 2+ ions per monomer. [4] There are several crystal structures of photosystem II. [5] The PDB accession codes for this protein are 3WU2, 3BZ1, 3BZ2 (3BZ1 and 3BZ2 are monomeric structures of the Photosystem II dimer), [4] 2AXT, 1S5L, 1W5C, 1ILX, 1FE1, 1IZL.