Реферат: Mitochondria 2 Essay Research Paper MitochondriaMitochondria are
Mitochondria 2 Essay, Research Paper
Mitochondria are tiny organelles found in nearly all eukaryotic cells. They are rather large organelles ranging from 0.5+m to 10+m in length and 1+m in diameter. The mitochondria are the energy factories of the cell and are located in the cytoplasm. They are the sites of cellular respiration. The mitochondria are responsible for generating ATP from such organic fuels as simple sugars and fats in the process of cellular respiration. This doubled-membrane organelle has its own DNA and can reproduce by splitting itself.
The mitochondria are sausage-shaped structures that move, change their shape and divide. They are distinct organelles with two membranes, the inner membrane and the outer membrane. The outer membrane is smooth and limits the organelle. It is highly permeable to small solutes such as molecules and ions, but it blocks off passages of proteins and other macromolecules.
The inner membrane of the mitochondria is folded into shelf like structures called cristae. The cristae does not even allow the passage of small ions and so it maintains a closed space within the cell. The many infoldings of the cristae are responsible for providing the mitochondrion with a large surface area which enhances the productivity of respiration.
The inner membrane and outer membrane effectively divide the mitochondria into two internal compartments. The space located between the outer and inner mitochondrial membrane is called the intermembrane space. The space enclosed by the inner membrane is called the mitochondrial matrix. It is here that many of the metabolic steps of cellular respiration occur.
The intermembrane space reflects the solute composition of the cytosol, because the outer membrane is permeable to small solute molecules. it has its own small group of enzymes, because the o outer membrane is not permeable to macromolecules.
The mitochondrial matrix contains enzymes that catalyse many metabolic steps of cellular respiration. Some enzymes are actually embedded in the inner membrane.
The purpose of the mitochondria is to power the cell. These organelles take in glucose and oxygen and break them down to provide ATP (a substance that is an important store of chemical energy for cells). This process is called cellular respiration.
They perform almost the exact opposite function of the chloroplasts, which provide all the materials necessary for cellular respiration through the process of photosynthesis. The chloroplasts develop the materials necessary for providing the cell with energy, and the mitochondria use the materials to manufacture it.
Cellular respiration takes place in three main stages. Each of these three stages is a complex biochemical pathway.
The first stage of cellular respiration is glycolysis, which take place outside of the mitochondrion. Glycolysis is the pathway by which a molecule of glucose is broken down into two molecules of pyruvate. During Glycolysis, the six-carbon glucose molecule is split into 2 three-carbon molecules. During this process energy is also given off. Some of this energy is lost as heat, some energy is used to make two ATPs, and some energy is stored temporarily in molecules of NADH.
Glycolysis takes place in the cytoplasm of the cell and does not require the presence of oxygen. Glycolysis is referred to as the anaerobic stage of cellular respiration since oxygen is not required.
The second and third stages of cellular respiration are the citric acid cycle (Krebs Cycle) and the electron transport chain. Unlike glycolysis, these stages are aerobic. This means that oxygen must be present for them to occur.
The second stage of cellular respiration, the Krebs cycle, converts pyruvic acid into carbon dioxide, and this takes place within the matrix of the mitochondria. In the Krebs cycle, the three carbon fragments are broken down into one carbon molecules of carbon dioxide. One ATP is produced for each three-carbon molecule. More NADH is also made during the Krebs cycle.
The final stage of cellular respiration is the electron transport chain which produces most of the ATP and is built into the cristae of the mitochondrion. During electron transport, the energy stored in the NADH made in glycolysis and the Krebs cycle is used to produce 32 more ATP molecules.
At the end of cellular respiration, each glucose molecule had been oxidized to carbon dioxide and a total of 36 ATPs are produced.
Cells that use energy at a high rate contain large numbers of mitochondria to make replacement ATP. Muscle cells and heart cells are cells with high energy requirements, that contain many mitochondria. Mitochondria have their own genetic material and can reproduce themselves within living cells. Most cells contain mitochondria which are organelles with elaborate internal membranes.