Oxygen CYCLE : Oxygen CYCLE K.DINESH BABU
II M.SC BT Slide 2: Oxygen is one of the constituents of water and form about 21% of the air in the atmosphere. It is required for respiration for all living organisms.
Oxygen cycle runs through the following process-By burning the materials to reduce oxygen combining with nitrogen to produce oxides of nitrogen, proteins, etc.
These compounds after breaking down releases oxygen in the atmosphere and maintain forever in the environment. Reservoirs of Oxygen : Reservoirs of Oxygen silicate and oxide minerals of the crust and mantle (99.5%)
atmospheric oxygen -photosynthesis
6CO2 + 6H2O + energy → C6H12O6 + 6O2
oxygen is lost from the atmosphere is via respiration and decay
Oxygen is also cycled between the biosphere and lithosphere : Step One of Oxygen Cycle : Step One of Oxygen Cycle Plant release oxygen into the atmosphere as a by-product of photosynthesis. oxygen Step Two of Oxygen Cycle : Step Two of Oxygen Cycle Animals take in oxygen through the process of respiration.
Animals then break down sugars and food. Step Three in Oxygen Cycle : Step Three in Oxygen Cycle Carbon dioxide is released by animals and used in plants in photosynthesis.
Oxygen is balanced between the atmosphere and the ocean. History of Oxygen : History of Oxygen Early evolution of Earth, oxygen released from H2O vapor by UV radiation and accumulated in the atmosphere as the hydrogen escaped into the earth's atmosphere
Photosynthesis became a source of oxygen
Oxygen released as organic carbon and gets buried in sediments. Photosynthesis : Photosynthesis Definition- process in which green plants use the energy from the sun to make carbohydrates from carbon dioxide and water in the presence of chlorophyll. How is Photosynthesis Carried Out? : How is Photosynthesis Carried Out? Photosynthesis only occurs in plants containing chlorophyll:
Water is absorbed by the roots and carried to the leaves by the xylem
Carbon dioxide is obtained from air that enters the leaves through the stomata and diffuses to the cells containing chlorophyll.
Chlorophyll is uniquely capable of converting the energy from light into a dormant form that can be stored and used when needed. Steps in Photosynthesis : Steps in Photosynthesis The light energy strikes the leaf, passes into the leaf and hits a chloroplast inside an individual cell
The light energy, upon entering the chloroplasts, is captured by the chlorophyll inside a grana.
Inside the grana some of the energy is used to split water into hydrogen and oxygen.
The oxygen is released into the air.
The hydrogen is taken to the stroma along with the grana's remaining light energy. Steps Continued: : Steps Continued: Carbon dioxide enters the leaf and passes into the chloroplast.
In the stroma the remaining light energy is used to combine hydrogen and carbon dioxide to make carbohydrates.
The energyrich carbohydrates are carried to the plant's cells.
The energyrich carbohydrates are used by the cells to drive the plant's life processes. Respiration : Respiration Process by which an organism exchanges gases with its environment
Process → oxygen is abstracted from air, transported to cells for the oxidation of organic molecules while CO2 and H2O, the products of oxidation, are returned to the environment Earth’s Layers : Earth’s Layers The lithosphere is Earth's surrounding layer, composed of solids such as soil and rock.
The atmosphere is the surrounding thin layer of gas.
The hydrosphere refers to liquid environments such as lakes and oceans that lie between the lithosphere and atmosphere.
The biosphere's creation and continuous existence results from chemical, biological, and physical processes. Today : Today The Earth’s atmosphere consists of:
The Earth’s lithosphere consists of:
The Earth’s hydrosphere consists of:
The Earth’s biosphere consists of:
0.01% Oxygen Biological Importance of Oxygen : Biological Importance of Oxygen Humans need it to breathe
Needed for decomposition of organic waste
Water can dissolve oxygen and it is this dissolved oxygen that supports aquatic life. The Nitrogen Cycle : The Nitrogen Cycle Atmospheric
and deposition Animal
and biosolids Industrial fixation
(commercial fertilizers) Crop
harvest Volatilization Denitrification Runoff and
erosion Leaching Organic
legume plants Plant
uptake Immobilization Mineralization Input to soil Component Loss from soil - + Why does atmospheric nitrogen need to be converted? : Why does atmospheric nitrogen need to be converted? N N N N N N It is one of nature’s great ironies… : It is one of nature’s great ironies… Nitrogen is an essential component of DNA, RNA, and proteins—the building blocks of life.
Although the majority of the air we breathe is nitrogen, most living organisms are unable to use nitrogen as it exists in the atmosphere! The largest single source of nitrogen is in the atmosphere. : The largest single source of nitrogen is in the atmosphere. Nitrogen makes up 78% of our air! Sources : Sources Lightning
Organic fertilizers Forms of Nitrogen : Forms of Nitrogen Urea CO(NH2)2
Ammonia NH3 (gaseous)
Atmospheric Dinitrogen N2
Organic N Global Nitrogen Reservoirs : Global Nitrogen Reservoirs Roles of Nitrogen : Roles of Nitrogen Plants and bacteria use nitrogen in the form of NH4+ or NO3-
It serves as an electron acceptor in anaerobic environment
Nitrogen is often the most limiting nutrient in soil and water. Nitrogen is a key element for : Nitrogen is a key element for amino acids
nucleic acids (purine, pyrimidine)
cell wall components of bacteria (NAM). Nitrogen Cycles : Nitrogen Cycles Ammonification/mineralization
Denitrification How does atmospheric nitrogen get changed into a form that can be used by most living organisms? : How does atmospheric nitrogen get changed into a form that can be used by most living organisms? N N By traveling through one of the four processes in the Nitrogen Cycle! : By traveling through one of the four processes in the Nitrogen Cycle! (1) Nitrogen Fixation (3) Nitrification (2) Ammonification (4) Denitrification Nitrogen Cycle What is “nitrogen fixation” and what does it mean to say nitrogen gets “fixed”? : What is “nitrogen fixation” and what does it mean to say nitrogen gets “fixed”? N N “Nitrogen Fixation” is the process that causes the strong two-atom nitrogen molecules found in the atmosphere to break apart so they can combine with other atoms. Nitrogen gets “fixed” when it is combined with oxygen or hydrogen. : “Nitrogen Fixation” is the process that causes the strong two-atom nitrogen molecules found in the atmosphere to break apart so they can combine with other atoms. Nitrogen gets “fixed” when it is combined with oxygen or hydrogen. N N N N N Oxygen Hydrogen Oxygen Hydrogen N How does nitrogen reenter the atmosphere in the nitrogen cycle? : How does nitrogen reenter the atmosphere in the nitrogen cycle? Through the fourth process called denitrification! : Through the fourth process called denitrification! (1) Nitrogen Fixation (2) Nitrification (3) Ammonification (4) Denitrification What does denitrification do? : What does denitrification do? Denitrification converts nitrates (NO3) in the soil to atmospheric nitrogen (N2) replenishing the atmosphere. : Denitrification converts nitrates (NO3) in the soil to atmospheric nitrogen (N2) replenishing the atmosphere. Nitrates (NO3) in Soil Nitrogen in atmosphere (N2) How does the denitrification process work? : How does the denitrification process work? Nitrates in soil Denitrifying bacteria live deep in soil and in aquatic sediments where conditions make it difficult for them to get oxygen. The denitrifying bacteria use nitrates as an alternative to oxygen, leaving free nitrogen gas as a byproduct. They close the nitrogen cycle! : Denitrifying bacteria live deep in soil and in aquatic sediments where conditions make it difficult for them to get oxygen. The denitrifying bacteria use nitrates as an alternative to oxygen, leaving free nitrogen gas as a byproduct. They close the nitrogen cycle! Denitrifying bacteria live deep in soil and use nitrates as an alternative to oxygen making a byproduct of nitrogen gas. Nitrogen in atmosphere closes the nitrogen cycle! (NO3) (N2) Ammonification or Mineralization : Ammonification or Mineralization R-NH2 NH4 NO2 NO3 NO2 NO N2O N2 Mineralization or Ammonification : Mineralization or Ammonification Decomposers: earthworms, termites, slugs, snails, bacteria, and fungi
Uses extracellular enzymes initiate degradation of plant polymers
Proteases, lysozymes, nucleases to degrade nitrogen containing molecules Slide 47: Plants die or bacterial cells lyse release of organic nitrogen
Organic nitrogen is converted to inorganic nitrogen (NH3)
When pH<7.5, converted rapidly to NH4
Urea NH3 + 2 CO2 Nitrogen Fixation : Nitrogen Fixation Energy intensive process :
N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi
Performed only by selected bacteria and actinomycetes
Performed in nitrogen fixing crops
(ex: soybeans) Microorganisms fixing : Microorganisms fixing Azobacter
Cyanobacteria Require the enzyme nitrogenase
Inhibited by oxygen
Inhibited by ammonia (end product) Rates of Nitrogen Fixation : Rates of Nitrogen Fixation Slide 51: Applications to wetlands : Applications to wetlands Occur in overlying waters
Leaf or stem surfaces of plants Nitrification : Nitrification R-NH2 NH4 NO2 NO3 NO2 NO N2O N2 Nitrification : Nitrification Two step reactions that occur together :
1rst step catalyzed by Nitrosomonas
2 NH4+ + 3 O2 2 NO2- +2 H2O+ 4 H+
2nd step catalyzed by Nitrobacter
2 NO2- + O2 2 NO3- Slide 55: Optimal pH is between 6.6-8.0
If pH < 6.0 rate is slowed
If pH < 4.5 reaction is inhibited Denitrification : Denitrification R-NH2 NH4 NO2 NO3 NO2 NO N2O N2 Denitrification : Denitrification Removes a limiting nutrient from the environment
4NO3- + C6H12O6 2N2 + 6 H20
Inhibited by O2
Not inhibited by ammonia
Nitrate is the terminal electron acceptor Looking at the Nitrogen cycle through the eye of NH4 : Looking at the Nitrogen cycle through the eye of NH4 The hydrologic cycle : The hydrologic cycle HYDROLOGIC CYCLE : HYDROLOGIC CYCLE The hydrologic cycle is the transfer of water from the oceans to the atmosphere to the land and back to the oceans in a system involving a number of major processes What percent of the Earth’s total volume of water is stored in the atmosphere? : What percent of the Earth’s total volume of water is stored in the atmosphere? 0.001%
Clouds Human factors affecting surface runoff : Human factors affecting surface runoff Urbanization -- more impervious surfaces reduce infiltration and accelerate water motion
Removal of vegetation and soil -- surface grading, artificial drainage networks increases volume of runoff and shortens runoff time to streams from rainfall and snowmelt ACTION SPEAKS LOUDER THAN WORDS : ACTION SPEAKS LOUDER THAN WORDS Slide 79: THANK U