The growth of all organisms depends on the availability of mineral nutrients, and none is more important than nitrogen, which is required in large amounts as an essential component of proteins, nucleic acids and other cellular constituents. There is an abundant supply of nitrogen in the earth’s atmosphere – nearly 79% in the form of N 2 gas. However, N 2 is unavailable for use by most organisms because there is a triple bond between the two nitrogen atoms, making the molecule almost inert. In order for nitrogen to be used for growth it must be ‘fixed’ (combined) in the form of ammonium (NH 4) or nitrate (NO 3) ions. The weathering of rocks releases these ions so slowly that it has a effect on the availability of fixed nitrogen.
So, nitrogen is often the limiting factor for growth and biomass production in all environments where there is suitable climate and availability of water to support life. Microorganisms have a central role in almost all aspects of nitrogen availability and thus for life support on earth: some bacteria can convert N 2 into ammonia by the process termed nitrogen fixation; these bacteria are either free-living or form symbiotic associations with plants or other organisms (e. g. termites, protozoa) other bacteria bring about transformations of ammonia to nitrate, and of nitrate to N 2 or other nitrogen gases many bacteria and fungi degrade organic matter, releasing fixed nitrogen for reuse by other organisms.
All these processes contribute to the nitrogen cycle. We shall deal first with the process of nitrogen fixation and the nitrogen-fixing organisms, then consider the microbial processes involved in the cycling of nitrogen in the biosphere. A relatively small amount of ammonia is produced by lightning. Some ammonia, also is produced industrially by the Haber-Bosch process, using an iron-based catalyst, very high pressures and fairly high temperature. But the major conversion of N 2 into ammonia, and thence into proteins, is achieved by microorganisms in the process called nitrogen fixation (or di nitrogen fixation).
The Term Paper on Cellular Processes
When molecules move from a high to low concentration it is called moving DOWN the concentration gradient. When molecules move from a low to high concentration it is called moving AGAINST the concentration gradient. When the concentration of a solute is the same throughout a system, the system is at EQUILIBRIUM. What kind of transport DOES NOT require energy? PASSIVEWhat kind of transport ...
Biological nitrogen fixation can be represented by the following equation, in which two moles of ammonia are produced from one mole of nitrogen gas, at the expense of 16 moles of ATP and a supply of electrons and protons (hydrogen ions): N 2 + 8 H+ + 8 e- + 16 ATP = 2 NH 3 + H 2 + 16 ADP + 16 Pi This reaction is performed exclusively by prokaryotes (the bacteria and related organisms), using an enzyme complex termed.
This enzyme consists of two proteins – an iron protein and a molybdenum-iron protein, as shown below. The reactions occur while N 2 is bound to the enzyme complex. The Fe protein is first reduced by electrons donated by. Then the reduced Fe protein binds ATP and reduces the molybdenum-iron protein, which donates 3 electrons to N 2, producing HN = NH. In two further cycles of this process (each requiring electrons donated by) HN = NH is reduced to H 2 N-NH 2, and this in turn is reduced to 2 NH 3. Depending on the type of microorganism, the reduced which supplies electrons for this process is generated by photosynthesis, respiration or fermentation..
