What Do Mitochondria Do In An Animal Cell
Mitochondrion Definition
The mitochondrion (plural mitochondria) is a membrane-bound organelle found in the cytoplasm of eukaryotic cells. It is the power business firm of the jail cell; it is responsible for cellular respiration and production of (most) ATP in the cell. Each cell can have from one to thousands of mitochondria. Mitochondria also comprise extranuclear DNA that encodes a number of rRNAs, tRNAs, and proteins.
The effigy depicts the general construction of a typical creature cell. The organelles are labelled.
Mitochondrion Origin
The current theory as to the origin of eukaryotic cells is endosymbiosis. It is believed that mitochondria (and chloroplasts) began as prokaryotic organisms that were living within larger cells. It is likely that these prokaryotic organisms were engulfed by the larger cells, either as food or parasites. At some point the relationship became mutually beneficial and the mitochondria and chloroplasts became a permanent feature in the cells. They were enclosed in membranes and formed cellular machinery.
Mitochondrion Structure
Mitochondria are small-scale membrane-bound organelles that are usually about 1 – 10 microns in length. They can exist spherical or rod-shaped. The mitochondrion is enclosed by two membranes that split it from the cytosol and the rest of the cell components. The membranes are lipid bilayers with proteins embedded inside the layers. The inner membrane is folded to form cristae; this increases the surface area of the membrane and maximizes cellular respiration output. The region between the 2 membranes is the intermembrane space. Inside the inner membrane is the mitochondrial matrix, and within the matrix there are ribosomes, other enzymes, and mitochondrial Deoxyribonucleic acid. The mitochondrion is able to reproduce and synthesize proteins independently. It contains the enzymes necessary for transcription, as well every bit the transfer RNAs and ribosomes required for translation and poly peptide formation.
The figure shows a cut-out of an animal mitochondrion. The major components are labelled.
Mitochondrial DNA
Mitochondrial DNA (mtDNA) is typically a small circular double-stranded Dna molecule that encodes a number of proteins and RNA involved primarily in cellular respiration and cell reproduction. In some protists and fungi, mtDNA can be linear. Mitochondrial DNA is well conserved inside taxa. For example, many birds or mammals have the same factor order. Animal mitochondrial DNA encodes two ribosomal RNAs, 22 transfer RNAs, and thirteen protein coding genes (subunits of NADH, ATPase, and cytochromes). It also consists of the not-coding control region, or D-loop, which is involved in the regulation of Dna replication.
Unlike nuclear Dna, which is passed on from both parents, mitochondrial Deoxyribonucleic acid is generally uniparentally inherited (with some notable exceptions). In animals mtDNA is passed on maternally through the egg, except in bivalve molluscs where biparental inheritance is found. In plants mtDNA may be passed on maternally, paternally, or biparentally. In that location is also evidence for paternal leakage of mtDNA, where the offspring inherits most of their mtDNA from their mother but likewise receives a small amount from their father.
Mutations in mitochondrial DNA can result in a number of human genetic diseases, particularly those that involve energy consumption in the muscular and nervous systems. Examples include diabetes, heart disease, myoclonic epilepsy, Kearns-Sayre neuromuscular syndrome, and Alzheimer's. It has also been implicated in degenerative diseases and crumbling.
Compared to nuclear coding genes, animal mitochondrial DNA evolves almost 10 times more rapidly, assuasive changes to exist seen in a relatively short time frame. Information technology too mutates in a relatively clock-like fashion (with some exceptions). For this reason mitochondrial DNA is commonly used to study evolutionary relationships and population genetics in animals; it was the driving forcefulness behind the "Out-of-Africa" hypothesis of human evolution, also as the evolutionary relationship between humans and apes. Establish mtDNA evolves fairly slowly, and is less commonly used in evolutionary studies.
The figure shows the pocket-size round Dna molecules inside the organelles.
Mitochondrion Function
Mitochondria are involved in breaking down sugars and fats into energy through aerobic respiration (cellular respiration). This metabolic process creates ATP, the energy source of a cell, through a series of steps that crave oxygen. Cellular respiration involves three main stages.
The figure shows an overview of cellular respiration. Glycolysis takes identify in the cytosol while the Krebs cycle and oxidative phosphorylation occur in the mitochondria.
Glycolysis
Glycolysis occurs in the cytosol, splitting glucose into two smaller sugars which are then oxidized to class pyruvate. Glycolysis can exist either anaerobic or aerobic, and every bit such is non technically part of cellular respiration, although information technology is oft included. It produces a pocket-size amount of ATP.
During glycolysis the starting glucose molecule is phosphorylated (using 1 ATP molecule), forming glucose-six-phosphate, which so rearranges to its isomer fructose-six-phosphate. The molecule is again phosphorylated (using a second ATP molecule), this time forming fructose-1,6-bisphosphate. Fructose-ane,6-bisphosphate is then split into two 3-carbon sugars which are converted to pyruvate molecules through a redox reaction, which produces ii NADH molecules, and substrate-level phosphorylation, which releases iv molecules of ATP. Glycolysis produces a internet two ATP molecules.
Citric Acid Bike
In the presence of oxygen, the pyruvate molecules produced in glycolysis enter the mitochondrion. The citric acid cycle, or Krebs wheel, occurs in the mitochondrial matrix. This process breaks down pyruvate into carbon dioxide in an oxidation reaction. The citric acrid bicycle results in the formation of NADH (from NAD+) which transports electrons to the final stage of cellular respiration. The citric acid cycle produces two ATP molecules.
Pyruvate enters the mitochondrion and is converted into acetyl coenzyme A. This conversion is catalyzed by enzymes, produces NADH, and releases COtwo. The acetyl group then enters the citric acid cycle, a series of eight enzyme-catalyzed steps that begins with citrate and ends in oxaloacetate. The addition of the acetyl group to oxaloacetate forms citrate and the bicycle repeats. The breakup of citrate into oxaloacetate releases a farther two CO2 molecules and one molecule of ATP (through substrate-level phosphorylation). The majority of the free energy is in the reduced coenzymes NADH and FADH2. These molecules are then transported to the electron transport chain.
The figure shows the conversion of pyruvate into acetyl coenzyme A and its progression through the citric acid cycle.
Oxidative Phosphorylation
Oxidative phosphorylation consists of two parts: the electron transport chain and chemiosmosis. It is this terminal stage that produces the majority of the ATP in the respiration process. The electron ship chain uses the electrons carried forward from the previous two steps (as NADH and FADHii) to form water molecules through combination with oxygen and hydrogen ions. Oxidative phosphorylation occurs in the inner membrane of the mitochondrion.
The electron transport chain is fabricated upwardly of 5 multi-protein complexes (I to IV) that are repeated hundreds to thousands of times in the cristae of the inner membrane. The complexes are made upwardly of electron carriers that transport the electrons released from NADH and FADH2 through a serial of redox reactions. Many of the proteins found in the electron ship chain are cytochromes, proteins that are encoded for in part by mitochondrial Dna. As the electrons move forth the chain they are passed to increasingly more electronegative molecules. The last step is the transfer of the electron to an oxygen atom which combines with two hydrogen ions to form a water molecule. The electron send chain itself does not produce ATP.
ATP is produced via chemiosmosis, a process that also occurs in the inner membrane of the mitochondrion. Chemiosmosis involves the transmembrane protein ATP synthase which produces ATP from ADP and inorganic phosphate. ATP synthase uses the concentration gradient of hydrogen ions to bulldoze the germination of ATP. Every bit the electrons move through the electron transport chain, hydrogen ions are pushed out into the intermembrane space, producing a higher concentration of H+ exterior the membrane. The consumption of H+ through incorporation into water molecules further increases the concentration slope. The hydrogen ions and then effort to re-enter the mitochondrial matrix to equalize the concentrations; the simply place they tin can cross the membrane is through the ATP synthase. The flow of H+ through the enzyme results in conformational changes that provide catalytic agile sites for ADP and inorganic phosphate. When these 2 molecules bind to the ATP synthase they are connected and catalyzed to class ATP.
Oxidative phosphorylation produces between 32 and 34 ATP molecules from each initial glucose molecule, accounting for ~89% of the energy produced in cellular respiration.
Quiz
one. Which pace of cellular respiration produces the well-nigh ATP?
A. Krebs cycle
B. Glycolysis
C. Citric acid cycle
D. Chemiosmosis
two. Where does oxidative phosphorylation occur?
A. Mitochondrial matrix
B. Outer membrane
C. Inner membrane
D. Intermembrane space
3. What organisms do not contain mitochondria?
A. Plants
B. Animals
C. Bacteria
D. Fungi
References
- Boore, J. L. (1999). Animal mitochondrial genomes. Nucleic Acids Inquiry, 27, 1767-1780.
- Brown, W. Chiliad., George, K., & Wilson, A. C. (1979). Rapid evolution of animal mitochondrial Dna. Proceedings of the National University of Sciences USA, 76, 1967-1971.
- Campbell, N. A., & Reece, J. B. (2005).Biology, 7th. ed. Chs. 6, 9, and 26. San Francisco, CA: Benjamin Cummings. ISBN: 0-8053-7171-0.
- Cann, R. 50., Stoneking, M., & Wilson, A. C. (1987). Mitochondrial DNA and human evolution. [10.1038/325031a0]. Nature, 325, 31-36.
- Madigan, M. T., & Martinko, J. Chiliad. (2006).Brock biology of microorganisms, 11th. ed. Chs. 7 and 14. Upper Saddle River, NJ: Pearson Prentice Hall. ISBN: 0-thirteen-144329-ane.
- Wallace, D. C. (1999). Mitochondrial diseases in man and mouse. Scientific discipline, 283, 1482-1488.
Source: https://biologydictionary.net/mitochondrion/
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