Biological Sciences
Mitochondria and Chloroplasts
Mitochondria and chloroplasts are organelles found in eukaryotic cells. Mitochondria are responsible for producing energy in the form of ATP through cellular respiration, while chloroplasts are involved in photosynthesis, converting light energy into chemical energy in the form of glucose. Both organelles have their own DNA and are believed to have originated from endosymbiotic relationships with ancient prokaryotic cells.
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10 Key excerpts on "Mitochondria and Chloroplasts"
eBook - PDF- Rodney P. Anderson, Linda Young, Kim R. Finer(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
Think Critically Why do these two organelles have inner and outer membranes? Outer chloroplast envelope Fret Stroma Inner chloroplast envelope Granum Thylakoid a. Mitochondria are the site of aerobic respiration; the production of ATP from the breakdown of glucose. The inset photo shows a TEM of a mitochondrion. b. Chloroplasts exist in plants and algae only. They are the site of photosynthesis; the production of ATP and glucose from water and carbon dioxide using light energy. In mitochondria the inner membrane contains folds called cristae (singular crista), and the area inside the inner membrane is called the matrix. The folds of the cristae greatly increase the surface area of the inner membrane. Movement of protons from the matrix across the inner membrane and back again into the matrix generates adenosine triphosphate (ATP). This proton movement is an important step in the process of cellular respiration, a series of reactions that extracts stored energy from the chemical bonds of glucose producing ATP. Chloroplasts harvest solar energy and transform it into chemical energy via photosynthesis. Chloroplasts are typically larger than mitochondria and have both an inner and outer membrane. In chloroplasts the inner membrane surrounds a large space called the stroma, which is anal- ogous to the mitochondrial matrix. Inside the stroma are flat stacks of membranes called thylakoids. A stack of thylakoids forms a granum (plural grana), and the granal stacks hold chlorophyll, which is the light-collecting pig- ment of photosynthesis. Plant cells use the ATP generated in the initial reactions of photosynthesis to harvest carbon from CO 2 and produce needed organic compounds, includ- ing glucose, for a variety of cellular processes. Both cellular respiration and photosynthesis are discussed in detail in Chapter 11. The Cytoskeleton Three different fibrous protein structures make up the cytoskeleton, a protein-based network that functions in cell support and movement.
eBook - ePub- Britannica Educational Publishing, Kara Rogers(Authors)
- 2010(Publication Date)
- Britannica Educational Publishing(Publisher)
Mitochondria and Chloroplasts are the powerhouses of the cell. Mitochondria appear in both plant and animal cells as elongated cylindrical bodies, roughly one micrometre in length and closely packed in regions actively using metabolic energy. Mitochondria oxidize the products of cytoplasmic metabolism to generate ATP, the energy currency of the cell. Chloroplasts are the photosynthetic organelles in plants and some algae. They trap light energy and convert it partly into ATP but mainly into certain chemically reduced molecules that, together with ATP, are used in the first steps of carbohydrate production. Mitochondria and Chloroplasts share a certain structural resemblance, and both have a somewhat independent existence within the cell, synthesizing some proteins from instructions supplied by their own DNA.Mitochondrial and Chloroplastic Structure
Both organelles are bounded by an external membrane that serves as a barrier by blocking the passage of cytoplasmic proteins into the organelle. An inner membrane provides an additional barrier that is impermeable even to small ions such as protons. The membranes of both organelles have a lipid bilayer construction. Located between the inner and outer membranes is the intermembrane space.In mitochondria the inner membrane is elaborately folded into structures called cristae that dramatically increase the surface area of the membrane. In contrast, the inner membrane of chloroplasts is relatively smooth. However, within this membrane is yet another series of folded membranes that form a set of flattened, disklike sacs called thylakoids. The space enclosed by the inner membrane is called the matrix in mitochondria and the stroma in chloroplasts. Both spaces are filled with a fluid containing a rich mixture of metabolic products, enzymes, and ions. Enclosed by the thylakoid membrane of the chloroplast is the thylakoid space. The extraordinary chemical capabilities of the two organelles lie in the cristae and the thylakoids. Both membranes are studded with enzymatic proteins either traversing the bilayer or dissolved within the bilayer. These proteins contribute to the production of energy by transporting material across the membranes and by serving as electron carriers in important oxidation-reduction reactions.The internal membrane of a mitochondrion is elaborately folded into structures known as cristae. Cristae increase the surface area of the inner membrane, which houses the components of the electron-transport chain. Proteins known as F
eBook - PDF- Rathoure, Ashok Kumar(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
These captured plastids are known as kleptoplastids. Chloroplast Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of A TP and reduce NADP to NADPH through a complex set of processes called photosynthesis. The word chloroplast is derived from the Greek words chloros which means green and plast which means form or entity. Chloroplasts are members of a class of organelles known as plastids. This ebook is exclusively for this university only. Cannot be resold/distributed. Figure 2.18: Chloroplast Evolutionary Origin of Chloroplasts : Chloroplasts are one of the many different types of organelles in the cell. They are generally considered to have originated as endosymbiotic cyanobacteria i.e . blue-green algae. This was first suggested by Mereschkowsky in 1905 after an observation by Schimper This ebook is exclusively for this university only. Cannot be resold/distributed. in 1883 that chloroplasts closely resemble cyanobacteria. All chloroplasts are thought to derive directly or indirectly from a single endosymbiotic event in the Archaeplastida, except for Paulinella chromatophora , which has recently acquired a photosynthetic cyanobacterial endosymbiont which is not closely related to chloroplasts of other eukaryotes. In that they derive from an endosymbiotic event, chloroplasts are similar to mitochondria but chloroplasts are found only in plants and protista. The chloroplast is surrounded by a double-layered composite membrane with an intermembrane space; further, it has reticulations or many infoldings, filling the inner spaces. The chloroplast has its own DNA which codes for redox proteins involved in electron transport in photosynthesis. In green plants, chloroplasts are surrounded by two lipid-bilayer membranes. The inner membrane is now believed to correspond to the outer membrane of the ancestral cyanobacterium.
eBook - PDFThe Plant Cell
A Comprehensive Treatise
- N. E. Tolbert(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
Especially among the algae with large chloroplasts, plastids could be seen to divide and the division products were apportioned to the daughter cells. Observations of this sort led early microscopists to suggest that organelles such as the chloroplasts might have some degree of autonomy and resemble cells within cells. It was but a step from here to suggest that such organelles might have arisen from the endosymbiotic invasion of one cell by another; for example, the plastid might have originated from the establishment of a blue-green algal (cyanobacterial) cell within a eukaryotic cell lacking plastids (see Margulies, 1970, for review). Similar conclusions about the mitochondrion had to await the development of the electron micro-scope since this organelle is close to the limit of resolution of the light micro-scope. We now know that mitochondria actively divide and fragment and, in the spectacular movies of tobacco leaf cells taken by Wildman (Wildman et al., 1962), can also be seen to associate with and disassociate themselves from the plastids in the light microscope. In synchronous cells of algae, plastids and mitochondria can be seen to associate into larger rings and then disassociate at various phases of the cell cycle (Lefort-Tran, 1975). Thus, these organelles are in a dynamic state, dividing, fusing, and moving about. The amount of mitochondrial material can be changed in response to envi-ronmental needs; for example, in Euglena cells where photosynthesis has been eliminated by dark growth and the cells are dependent on respiration, a hypertrophy of mitochondria is observed (Lefort, 1964). Further evidence came from genetic studies. Mendel's work was done in the nineteenth century at the same time that the early cytological studies of organelles were undertaken.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- College Publishing House(Publisher)
Where chloroplasts are inherited only from the female, transgenes in these plastids cannot be disseminated by pollen. This makes plastid transformation a valuable tool for the creation and cultivation of genetically modified plants that are biologically contained, thus posing significantly lower environmental risks. This biological containment strategy is therefore suitable for establishing the coexistence of conventional and organic agriculture. While the reliability of this mechanism has not yet been studied for all relevant crop species, recent results in tobacco plants are promising, showing a failed containment rate of transplastomic plants at 3 in 1,000,000. Mitochondrion Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy. ________________________ WORLD TECHNOLOGIES ________________________ Schematic of typical animal cell, showing subcellular components. Organelles: (1) nucleolus (2) nuclear membrane (3) Ribosomes (4) Vesicle (5) Rough endoplasmic reticulum (ER) (6) Golgi body (7) Cytoskeleton (8) Smooth ER (9) Mitochondria (13) Centrioles within centrosome In cell biology, a mitochondrion (plural mitochondria ) is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 10 micrometers (μm) in diameter. Mitochondria are sometimes described as cellular power plants because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. In addition to supplying cellular energy, mitochondria are involved in a range of other processes, such as signaling, cellular differentiation, cell death, as well as the control of the cell cycle and cell growth. Mitochondria have been implicated in several human diseases, including mitochondrial disorders and cardiac dysfunction, and may play a role in the aging process. The word mitochondrion comes from the Greek μίτος or mitos , thread + χονδρίον or chondrion , granule.
eBook - PDF- E. Broda(Author)
- 2014(Publication Date)
- Pergamon(Publisher)
The capacity for respiration, universally shown by contemporary blue-greens [14d, has also disappeared [18g. ORIGIN OF Mitochondria and Chloroplasts 127 Acquisition of cyanelles has never been reported for cells of higher plants. They may be excessively differentiated. Alternatively, it may not have been possible to distinguish cyan-elles from chloroplasts in this case. It appears that chloroplasts can live for weeks as sym-biotic organelles in cells of the digestive tract of slugs (Kawaguti and Yamasu, 1965; Taylor, 1970; Trench, 1971).These animals have special mechanisms for the placement of the chloroplasts. It is also possible to introduce chloroplasts (from spinach or violets) artificially into mammalian cells in culture, where they remain viable during some cell divisions at least (Nass, 1969b). In hens' eggs even a division of chloroplasts has been observed (Giles and Sarafis, 1974). Not only prokaryotic but also eukaryotic algae, e.g. species of Chlorella, occur as endo-symbionts of many invertebrates (for protozoa, see, for example, Ball, 1969; Karakashian, 1970; Taylor, 1973). Under conditions of normal food supply they also divide more or less in step with the host cell (Karakashian, 1970; see Smith, 1973a). (Their chloroplasts would then have to be considered as (degenerated) symbionts of a second order!) In fact, the symbiosis of (green) algae with protozoa appears so welcome to the latter that the absorption of the algae may be genetically regulated by the host. Thus Chlorella can multiply inside Paramecium bursaria (Margulis, 1970, on the basis of Karakashian [1963] and Karakashian and Siegel [1965]): . . . . only until the normal, genetically regulated number of algae per Paramecium is attained. The multiplication then stops. Should the protozoon encounter free-living Chlorellae, they are promptly digested. Its own algal partners, however, are totally immune.
eBook - ePub- Martin J. Hodson, John A. Bryant(Authors)
- 2012(Publication Date)
- Wiley-Blackwell(Publisher)
Thus, fatty acid oxidation, which in animals takes place in the mitochondria, takes place in plants within the peroxisomes/glyoxysomes (section 2.10). Mitochondria participate with chloroplasts and peroxisomes in photorespiration (Chapter 7, section 7.5). Intriguingly, the final step in ascorbate biosynthesis takes place in the mitochondrial inter-membrane space, mediated by an enzyme located in the inner membrane (see section 2.14.7). Mitochondria also export metabolites from the TCA (Krebs) cycle for use in other metabolic pathways. In addition, they possess all the biochemical machinery associated with DNA replication, gene expression and protein synthesis. As with chloroplasts, mitochondrial genomes are much smaller than those of their endosymbiotic ancestors; extensive transfer of genes from the mitochondrion to the nucleus has occurred during evolution. Current estimates suggests that angiosperm mitochondrial DNA contains genes for about 35 proteins, plus ribosomal and transfer RNAs. A fully functional mitochondrion needs several hundred proteins, implying that, as with chloroplasts, products of nuclear-located genes must be transferred into the organelle (Chapter 3, section 3.3.3). 2.7 The Nucleus Although the evolutionary origin of the nucleus remains a mystery, as was noted in Chapter 1 (section 1.3), its presence is one of the hallmarks of eukaryotic cells. Indeed, it may have evolved, along with other essentially eukaryotic features, before the first engulfment event. It is undoubtedly a complex organelle and its envelope alone has been the subject of scientific conferences and books. As shown diagrammatically in Figure 2.15, the nuclear envelope (NE) may be thought of as consisting of three membranous components. The first of these is the outer envelope, which is connected to the ER and, especially, to the rough ER (section 2.9.1). Indeed, like the rough ER, there may be ribosomes on the surface of the outer NE
eBook - ePub- Geoffrey H. Bourne(Author)
- 2014(Publication Date)
- Academic Press(Publisher)
FOUR Mitochondria Publisher Summary The mitochondrion is the only structure in the nucleated animal cell that satisfies both the biochemical structural criteria for an evolutionary relationship with bacteria. Mitochondria have most of the requirements for an independent existence, although they are not able to synthesize some essential compounds, but many symbiotic and parasitic organisms have lost functions they obviously possessed prior to evolving their dependent form of life. In the cells of animals and plants, the distribution of mitochondria varies with the function of the cell. In cell division, mitochondria tend to break up into small granules during the prophase and become passively distributed more or less evenly between the two daughter cells. In living tissue culture cells, the mitochondria undergo continuous movement. These movements may be fitful individual movements by the mitochondrion itself or may consist of movement of the whole mitochondrion through the cytoplasm of the cell. IN the latter half of the 19th century, cytologists described a number of structures in cells that were probably mitochondria. Kolliker in 1850 described structures in muscle that were probably sarcosomes (muscle mitochondria). In the early part of the decade 1880–1890, Flemming described in cells some structures of a filamentous nature that were probably mitochondria, their official discovery is, however, usually attributed to Altmann in 1886, and they were put more or less definitely on the cytological map by Benda in 1903. They can be easily displayed with suitable dyes. Altmann’s aniline fuchsine–picric acid technique shows them up very well. Regaud’s iron–hematoxylin method is also very good. The mitochondria can even be seen in the living cell by staining them intravitally with Janus green and, of course, they show up extremely well with the phase-contrast and interference microscopes. There is not much difficulty, then, in establishing their existence and nature
eBook - PDFMitochondria in Higher Plants
Structure, Function, and Biogenesis
- Roland Douce(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Since the mechanism and physiological significance of these movements remain largely unexplained, we now need to establish more precisely how the controls of mitochondrial shape or fusion operate. We believe that the mitochondrial micro-morphology is very delicate and that mitochondria are the organelles that are the most sensitive indicators of outside influence. The observa-tions that 2,4-dinitrophenol and ATP cause pronounced changes in mi-tochondrial forms and movements, as does anaerobiosis, strongly sug-gest that the shape and probably the volume of mitochondria in situ are linked to respiration and phosphorylation (Frederic, 1958). In addition, it is possible that the shape of the mitochondria is partially attributable to local cytoplasmic constraints because isolated mitochondria are spherical. 2. Numbers The number of mitochondria per cell in higher plants is likely to be in the hundreds of even thousands depending on the size and type of cell and the extent of cell differentiation. In stereological analysis of electron micrographs of sycamore cells during their exponential phase of growth, in which mitochondria are spheres or small rods, we have found 250 mitochondria per cell. These mitochondria contain from 6 to 7% of the total protein of the cell and occupy, on the average, 0.7% of the total volume of the cell (including the vacuole space) and some 7% of the total cytoplasmic volume. In very active plant cells, like secretory cells in nectaries (Gunning and Steer, 1975) or anther stalks of grasses (Ledbet-ter and Porter, 1970), the proportion is much higher and can match that of animal cells. The cytoplasm of very active cells, like transfer cells and companion cells (i.e., cells that have the greater sustained demands for energy transduction in connection with the secretory process or the transport of solutes at the cell surface), is richly endowed with mito-chondria (Gunning and Steer, 1975).
eBook - PDF- Ruth Sager(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Acad. Sei. Symp. North-Holland Publ., Amsterdam. Goodwin, T. W., ed. (1967). 'Biochemistry of Chloroplasts, Vols. I and II. Academic Press, New York. Kirk, J. T. O. (1971). Chloroplast structure and biogenesis. Annu. Rev. Biochem. 21, 11. Kirk, J. T. O., and Tilney-Bassett, R. A. E., eds. (1966). The Plastids, pts. I, III, and IV. W. H. Freeman, London. Miller, P. L., ed. (1970). Control of Organelle Development, Soc. Exp. Biol. Symp., Vol. 24. Cambridge Univ. Press, London. References 1. Anderson, J. M., and Boardman, Ν. K. (1966). Fractionation of the photochemical systems of photosynthesis. I. Chlorophyll contents and photochemical activities of particles isolated from spinach chloroplasts. Biochim. Biophys. Acta 112, 403. la. App, Α. Α., and Jagendorf, A. T. (1964). 1 4 C-amino acid incorporation by spinach chloroplast preparation. Plant Physiol. 39, 772. 2. Arntzen, C. J., Dilley, R. Α., and Crane, F. L. (1969). A comparison of chloroplast membrane surface visualized by freeze-etch and negative staining techniques; and ultrastructural characterization of membrane fractions obtained from digiton in-treated spinach chloroplasts. /. Cell Biol. 43, 16. 3. Bennun, Α., and Avron, M. (1964). Light-dependent and light-triggered adenosine triphosphatase in chloroplasts. Biochim. Biophys. Acta 79, 646. 4. Benson, A. A. (1964). Plant membrane lipids. Annu. Rev. Plant Physiol. 15, 1. 5. Benson, Α. Α., Gee, R. W., Ji, T-H., and Bowes, G. W. (1971). Lipid-protein interac-tions in chloroplast lamellar membranes as bases for reconstruction and bio-synthesis. In Autonomy and Biogenesis of Mitochondria, and Chloroplasts, Aust. Acad. Sei. Symp. (Ν. K. Boardman, A. W. Linnane, and R. M. Smillie, eds.). pp. 18-26. North-Holland Publ. Amsterdam. 6. Bird, I. F., Porter, Η. K., and Stocking, C. R. (1965). Intracellular localization of en-zymes associated with sucrose synthesis in leaves. Biochim. Biophys. Acta 100, 366. 7. Bloch, K., Constantopoulos, G., Kenyon, C , and Nagai, J.
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