Structure and function of chloroplast pdf
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- Structure and function of the chloroplast signal recognition particle
- Chloroplasts – Structure and Functions
Structure and function of the chloroplast signal recognition particle
The targeting of proteins, including the insertion and translocation of proteins in or across membranes, is a fundamental process within a cell, and a variety of specialized mechanisms for protein transport have been developed during evolution. The signal recognition particle SRP is found in the cytoplasm of most, if not all, eukaryotes and prokaryotes where it plays a central role in the co-translational insertion of membrane proteins into the endoplasmic reticulum and plasma membrane, respectively. Interestingly, chloroplasts contain a specialized type of signal recognition particle. A mechanism of protein transport that has been extensively studied is the co-translational protein transport to the endoplasmic reticulum ER of eukaryotic cells. The cytosolic components, as well as the membrane components like the receptors and the translocation pore, have been characterized reviewed in Martoglio and Dobberstein ; Rapoport et al. The targeting process is initiated when the signal peptide of the protein emerges from the ribosome and is recognized by the signal recognition particle SRP. Upon dissociation of SRP from the signal peptide, translation resumes and the protein is translocated co-translationally through the translocation pore Sec61p into the ER, and SRP dissociates from the receptor in a GTP requiring step.
Chloroplast , structure within the cells of plants and green algae that is the site of photosynthesis , the process by which light energy is converted to chemical energy , resulting in the production of oxygen and energy-rich organic compounds. Photosynthetic cyanobacteria are free-living close relatives of chloroplasts; endosymbiotic theory posits that chloroplasts and mitochondria energy-producing organelles in eukaryotic cells are descended from such organisms. Chloroplasts are present in the cells of all green tissues of plants and algae. Chloroplasts are also found in photosynthetic tissues that do not appear green, such as the brown blades of giant kelp or the red leaves of certain plants. Chloroplasts are green because they contain the pigment chlorophyll , which is vital for photosynthesis.
The primary energy resource of life on earth is the sun, whose energy is captured in the form of usable carbons by a process called photosynthesis. Photosynthesis occurs within a cellular organelle adapted to that purpose, called the chloroplast. Chloroplasts are unique metabolic and sensory organelles restricted to plants, algae, and a few protists. In this special topic, we aimed to gather new research, hypotheses, and reviews that would help us to better understand the important role of chloroplasts in all photosynthetic organisms. We were fortunate enough to have submissions from many talented chloroplast researchers.
Chloroplasts carry out a number of other functions, including fatty acid synthesis , much amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to in plants like Arabidopsis and wheat. A chloroplast is a type of organelle known as a plastid , characterized by its two membranes and a high concentration of chlorophyll. Other plastid types, such as the leucoplast and the chromoplast , contain little chlorophyll and do not carry out photosynthesis. Chloroplasts are highly dynamic—they circulate and are moved around within plant cells, and occasionally pinch in two to reproduce.
In this review, we consider a selection of recent advances in chloroplast biology. These include new findings concerning chloroplast evolution, such as the identification of Chlamydiae as a third partner in primary endosymbiosis, a second instance of primary endosymbiosis represented by the chromatophores found in amoebae of the genus Paulinella , and a new explanation for the longevity of captured chloroplasts kleptoplasts in sacoglossan sea slugs. Other topics covered in this review include new protein components of nucleoids, an updated inventory of the chloroplast proteome, new enzymes in chlorophyll biosynthesis and new candidate messengers in retrograde signaling. Finally, we discuss the first successful synthetic biology approaches that resulted in chloroplasts in which electrons from the photosynthetic light reactions are fed to enzymes derived from secondary metabolism. Other major photosynthetic eukaryotic lineages arose when eukaryotic hosts engulfed a free-living photosynthetic eukaryote e.
Gene expression in chloroplasts is controlled primarily through the regulation of translation. This regulation allows coordinate expression between the plastid and nuclear genomes, and is responsive to environmental conditions. Despite common ancestry with bacterial translation, chloroplast translation is more complex and involves positive regulatory mRNA elements and a host of requisite protein translation factors that do not have counterparts in bacteria. Previous proteomic analyses of the chloroplast ribosome identified a significant number of chloroplast-unique ribosomal proteins that expand upon a basic bacterial 70S-like composition. In this study, cryo-electron microscopy and single-particle reconstruction were used to calculate the structure of the chloroplast ribosome to a resolution of
Functions of Chloroplast: Absorption of light energy and conversion of it into biological energy. Production of NAPDH2 and evolution of oxygen through the process of photosys of water. Production of ATP by photophosphorylation. NADPH2 and ATP are the assimilatory powers of photosynthesis.
Chloroplasts – Structure and Functions
Chloroplasts are plant cell organelles that convert light energy into relatively stable chemical energy via the photosynthetic process. By doing so, they sustain life on Earth. Chloroplasts also provide diverse metabolic activities for plant cells, including the synthesis of fatty acids, membrane lipids, Chloroplasts also provide diverse metabolic activities for plant cells, including the synthesis of fatty acids, membrane lipids, isoprenoids, tetrapyrroles, starch, and hormones. The biogenesis, morphogenesis, protection and senescence of chloroplasts are essential for maintaining a proper structure and function of chloroplasts, which will be the theme of this Research Topic.
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