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A chloroplast (/ ˈ k l ɔːr ə ˌ p l æ s t,-p l ɑː s t /) [1] [2] is a type of organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. Chloroplasts have a high concentration of chlorophyll pigments which capture the energy from sunlight and convert it to chemical energy and release oxygen.
Like mitochondria, chloroplasts have a double-membrane envelope, called the chloroplast envelope, but unlike mitochondria, chloroplasts also have internal membrane structures called thylakoids. Furthermore, one or two additional membranes may enclose chloroplasts in organisms that underwent secondary endosymbiosis , such as the euglenids and ...
The structure and function of cytochrome b 6 f (in chloroplasts) is very similar to cytochrome bc 1 (Complex III in mitochondria). Both are transmembrane structures that remove electrons from a mobile, lipid-soluble electron carrier (plastoquinone in chloroplasts; ubiquinone in mitochondria) and transfer them to a mobile, water-soluble electron ...
Plastids function to store different components including starches, fats, and proteins. [9] All plastids are derived from proplastids, which are present in the meristematic regions of the plant. Proplastids and young chloroplasts typically divide by binary fission, but more mature chloroplasts also have this capacity.
Eukaryotic cells contain organelles including mitochondria, which provide energy for cell functions; chloroplasts, which create sugars by photosynthesis, in plants; and ribosomes, which synthesise proteins. Cells were discovered by Robert Hooke in 1665, who named them after their resemblance to cells inhabited by Christian monks in a monastery.
Chloroplasts also need to balance the ratios of photosystem I and II for the electron transfer chain. The redox state of the electron carrier plastoquinone in the thylakoid membrane directly affects the transcription of chloroplast genes encoding proteins of the reaction centers of the photosystems, thus counteracting imbalances in the electron ...
Two families of reaction centers in photosystems can be distinguished: type I reaction centers (such as photosystem I in chloroplasts and in green-sulfur bacteria) and type II reaction centers (such as photosystem II in chloroplasts and in non-sulfur purple bacteria). The two photosystems originated from a common ancestor, but have since ...
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.