Similarities between chloroplast and mitochondria: mitochondria and chloroplast both are membrane-bound cell organelles.
CHLOROPLAST:-
Chloroplasts were first described by Nehemiah Grew and Antony Van Leeuwenhoek in the 17th century. Dutrochet in 1837 observed that chlorophyll is essential for 02 evolution of plants. Meyer first described the structure of chloroplast in 1883. Chloroplasts belong to the group of plastids, a term coined by Schimper in 1883.
Chloroplasts are characterized by the presence of green chlorophyll pigments. There are several types of plastids, which are classified as per the presence or absence of pigments, viz., proplastid, amyloplast, leucoplast, elioplast, chloro-amyloplast, chromoplast, chloroplast, pheoplast, rhodoplast, etc.
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| Chloroplast structure |
Structure: Chloroplast is in many ways similar to mitochondria, both of these are involved in the generation of metabolic energy, contain their own genome, and perform various critical functions. plant chloroplasts are large organelles (5-10 um long) Bounded by a double mem- brane-chloroplast envelope. Besides these two, chloroplast has a third inner membrane system- thylakoid membrane; this forms a network of flattened discs called thylakoids. Thylakoids are arranged in stacks called grana. These three membranes divide chloroplasts into three different compartments.
(1) Intermembrane space between two membranes of chloroplasts envelope.
(2) Stroma which lies inside the envelope but outside the grana.
(3) Thylakoid lumen.
Chloroplast is rich in proteins, lipids, carbohydrates, nucleic acids, minerals, and pigments. They also contain phospholipids such as phosphatidyl glycerol, phosphatidic acid, inositol, and ethanol amine. DNA & RNA are also associated with chloroplasts. As chloroplasts synthesize stretch, they store carbohydrates. Haeme and Chlorophyll are the major pigments in chloroplasts, but chlorophyll-A is more prominent. Several elements in free or bound form like copper, iron, magnesium, and manganese are present in this organelle.
Chloroplast DNA (ct DNA) is present in the stroma and is capable of coding about 150 proteins which are necessary for photosynthesis and the synthesis of carbohydrates and lipids. As chloroplast DNA alone is not capable of synthesizing all proteins, it is partly controlled by nuclear DNA. There is a close correlation between ct DNA diversity and speciation in higher plants.
FUNCTIONS OF CHLOROPLASTS
1. Photosynthesis: During photosynthesis energy from sunlight is utilized to drive the synthesis of glucose from CO2 and H2O. Photosynthesis takes place in two distinct stages a) The light reaction and b) the dark reaction. in the light reaction. energy from sunlight drives the synthesis of ATP and NADPH coupled to the formation of 02 from H2O. In the dark reaction which does not require sunlight. The ATP and NADPH produced by light reactions drive glucose synthesis. The light reactions occur in the thylakoid and the dark reactions in the stroma.
ATP SYNTHESIS
ATP synthesis in chloroplast also occurs with the help of the enzyme ATP synthase as in mitochondria. The energy here is stored in the proton gradient across the thylakoid membrane, unlike the inner mitochondrial membrane.
Microtubules: Derobertis and Franchi in 1953 identified microtubules in nerer cells which were called microtubules or nerve tubules. Sabatini, Bansch, and Barnette in 1963 have explained the actual structure of microtubules. Ledbetter and Porter have found microtubules in plant cells. Microtubules are found in cilia, flagella, basal granules, Centrioles, Kinetochore, polar caps in plants, Spindle fibers; axoneme in protozoa, cortex of meristematic cells in plants and elongated cells like lens cells and sperms.
FUNCTIONS OF CHLOROPLAST
Microtubules help in the movement of Cilia, and Flagella, Cyclosis or Cytoplasmic streaming, maintaining the cell structure movement of chromosomes during cell division, the division of the cell during cytokinesis. Microtubules are involve in shaping the cell during cell differentiation. Further, they help protozoans to procure their food, and transport of particulate matter, including the determination of intrinsic polarity in certain cells.
Microfilaments: Microfilaments consist of Actin Filaments which are smaller in structure than microtubules and very active. They were first observed in muscle cells in 1947.
Actin Filaments consist of monomers. They are proteinaceous in nature and each actin monomer is known as G-Actin (Globular Actin) which polymerizes to form F- actin (Filamentous actin). Each G-actin is made up of 375 amino acids. Association and Dissociation are dependent upon Cation concentration. The polymerization of monomers is also helped by Actin binding proteins. The actin monomers attached to ATP residues mainly attack at the positive end. While the actin monomers with ADP residues are no residue remaining at the -ve end, There is a rotation of 160 in between one molecule and another when an actin filament is formed which results in the formation of a double-stranded helix-like appearance.
Mitochondria
Mitochondria:-
Mitochondria were first described by Altmann in 1980 as Bioblasts. The term Mitochondrion was coined in 1897 by Benda. They are commonly referred to as powerhouses of the cell and specialize in the synthesis of adenosine triphosphate (ATP), the useful chemical form of energy.
They are present in all aerobic eukaryotic cells except in RBC. They are uniformly distributed in the cytoplasm. In some cases, they are located near the nucleus. In general, mitochondria are located near such structures where energy requirements are heavier.
Mitochondria contain their genetic system, which separate and distinct from the nuclear genome of the is cell, mitochondrial genomes are usually circular.
Functions: Oxidative phosphorylation. The majority of the usable energy obtained from the breakdown of carbohydrates or fats is derived by oxidative phosphorylation which occurs within the mitochondria. The breakdown of glucose by glycolysis and citric acid cycle views a total of four molecules of ATP and ten molecules of NADH and two molecules of FADH2. Other than the functions mentioned above, mitochondria also perform the following functions.
(1) Degradation of fats, carbohydrates, and proteins.
(2) Thermogenesis (heat Production).
(3) Biosynthetic activity (Starting the synthesis of Haem
(4) Storage of Catons
Cell organelles Golgi body and nucleus - Click here
