Biochemical Cycles Keisha Avallone

Water Cycle

AKA the Hydrologic Cycle


  • The path of water as it circulates between the land and the atmosphere
  • The sun provides heat to evaporate water from oceans, lakes, rivers, etc.
  • Plants also lose water to the air during transpiration
  • Water vapor condenses forming tiny droplets in cloudes
  • Precipitation occurs when clouds meet cool air and water falls from clouds to the earth
  • Some water is soaked into the ground and stuck between rock or clay this is groundwater
  • Most of the water flows downhill as runoff and eventually returns to the seas
  • The water is then evaporated again and begins the cycle again

Chemical Reactions:

No chemical reaction. Strictly physical changes.

Chemical Compound:


Organic vs Inorganic Components:

All components of the water cycle are inorganic.

Human Impact:

  • Human impact has resulted in changes in sea level, ocean salinity, and in biophysical properties of the land. These changes could eventually lead to climate changes.
  • Human regulation of river flow and vegetation clearing has reduced river runoff by about 324 km3 per year
  • Pesticides used by humans runoff into the water systems.

Carbon Cycle


  • The circulation and transformation of carbon between living things and the environment
  • Carbon compounds are present in living things and non living things.
  • Carbon moves from the atmosphere to plants (photosynthesis)
  • In the atmosphere, carbon is attached to oxygen in carbon dioxide (CO2)
  • With the sun, plants pull CO2 from the air to make food
  • Carbon moves from plants to animals (food chains)
  • When eaten, the plant's carbon is transferred to the animal that eats it
  • Animals also get carbon from other animals they eat
  • Carbon moves from plants and animals to the ground (death)
  • Decaying bodies of dead plants and animals bring carbon to the ground
  • Some become buried deep underground and will become fossil fuels in millions and millions of years
  • Carbon moves from living things to the atmosphere (respiration)
  • Humans and animals get rid of CO2, putting it back into the atmosphere
  • Carbon moves from fossil fuels to the atmosphere (burning)
  • Humans burn fossil fuels in plants and factories
  • Carbon moves from the atmosphere to the oceans
  • bodies of water soak up some carbon from the atmosphere

Chemical Reactions/Compounds:

  • Photosynthesis: 6CO2 + 12H2O + ENERGY ----> C6H12O6 + 6O2 + 6H2O
  • Combustion/Metabolism: CH4 + O2 ----> CO2 + H2O + ENERGY
  • Respiration: C6H12O6 + 6O2 ----> 6H2O + 6CO2 + ENERGY

Organic v. Inorganic Components:

Everything in the carbon cycle, except carbon dioxide.

Human Impact:

  • Burning fossil fuels
  • Being buried in the ground after death
  • Breathing

Nitrogen Cycle


  • Nitrogen is an essential component of RNA, DNA, and proteins
  • All organisms need nitrogen
  • Most of the air we breath is N2
  • Most nitrogen in the atmosphere is unavailable for use because of the strong triple bonds
  • To be used by organisms, nitrogen gas (N2) must be converted to ammonium (NH4+), nitrate (NO3-), or organic nitrogen ((NH2)2CO)
  • Nitrogen fixation
  • Process where N2 is converted to ammonium
  • Organisms get nitrogen directly from the atmosphere
  • Nitrogen-fixing inhabit legume root nodules and receive carbohydrates and a favorable environment from their host plant in exchange for some of the nitrogen they fix
  • High energy natural events such as lightning, forest fires, and even hot lava flows can cause the fixation of smaller amounts of nitrogen
  • Nitrogen uptake
  • The ammonium produced by nitrogen-fixing bacteria is usually quickly taken up and incorporated into proteins and other organic nitrogen compounds
  • When organisms near the top of the food chain eat, they take up nitrogen fixed by nitrogen-fixing bacteria
  • Nitrogen mineralization (decay)
  • After nitrogen is incorporated into organic matter, it is often converted back into inorganic nitrogen
  • When organisms die, decomposers consume the organic matter and lead to the process or decomposition
  • A significant amount of the nitrogen contained within the dead organisms is converted to ammonium
  • Nitrification
  • When it's in the form of ammonium, nitrogen is available for use by plants or for further transformation into nitrate (NO3-) through nitrification
  • The bacteria that carry out this reaction gain energy from it
  • Requires the presence of oxygen, so it can happen only in oxygen-rich environments
  • Ammonium ions are positively charged and therefore stick to negatively charged clay particles and soil organic matter
  • Positive charge prevents ammonium nitrogen from being washed out of the soil by rainfall
  • The negatively charged nitrate ion is not held by soil particles and so ban be washed out of the soil
  • Denitrification
  • oxidized forms or nitrogen such as nitrate (NO3-) and nitrate (NO2-) are converted to dinitrogen (N2) and, to a lesser extent, nitrous oxide gas (NO2)
  • Anaerobic process
  • Carried out by dentrifying bacteria which convert nitrate to dinitrate
  • Nitric oxide and nitrous oxide are gases that have environmental impacts
  • Nitric oxide contributes to smog and is an important greenhouse gas, thereby contributing to global warming

Chemical Reactions/Compounds:

  • Nitrogen Fixation: N2 + H2 ----> NH3
  • Ammonification: decomposers, bacteria, and fungi break down dead life into different plants, releasing ammonium into the soil
  • Nitrification: NH3 + NH4+ ----> NO2 ----> NO3
  • Denitrification: when there is no oxygen available, some bacteria will turn nitrate into nitrogen gas, which starts the cycle all over again

Organic v. Inorganic Components:

  • Nitrogen gas (N2): inorganic
  • Ammonia gas (NH3): inorganic
  • Ammonium ion (NH4+): inorganic
  • Nitric oxide (NO): inorganic
  • Nitrous oxide (N2O): inorganic
  • Nitrogen dioxide (NO2): inorganic
  • Nitrite (NO2-): inorganic
  • Nitrate (NO3-): inorganic

Human Impact:

  • German scientist (Fritz Haber) figured out how to short-circuit the nitrogen cycle by fixing nitrogen chemically at high temperatures and pressures, creating fertilizers that could be added to the soil directly. This led to an enormous boom in agriculture productivity, but this also had negative consequences. Wash off fields and into surface water or groundwater

Phosphorous Cycle


  • Phosphorus is an important element for all lifeforms
  • As phosphate (PO4) it makes up an important part of the structural framework that holds DNA and RNA together
  • Component of ATP as they serve as an energy release for organisms to use in building proteins or contacting muscles
  • Does not include a gas phase, but small particles make it to the atmosphere
  • Very little phosphorus circulates in the atmosphere because at earth's normal temperatures and pressures, phosphorus is not a gas
  • Phosphorus is mostly found in sedimentary rock
  • when it rains, phosphates are removed from the rocks and are distributed throughout sil and water
  • Plants take phosphate ions from the soil
  • The phosphates then move from plants to animals that eat them
  • Then it moves to other animals that eat those animals
  • The phosphates absorbed by animal tissue through consumption
  • Eventually returns to the soil through urine and feces
  • Also returns to the soil of decomposition of dead plants and animals

This video isn't the best, but it has the rock, so I did two :).

Chemical Reactions/Compounds:

  • P4 + 502 ----> P4010
  • P4 + 6F2 ----> 4PF3
  • P4 + 6Cl2 ----> 4PCl3
  • P4 + 6Br2 ----> 4PBr3
  • P4 + 6I2 ----> 4PI3

Organic v Inorganic Components:

  • Phosphate: inorganic
  • DNA/RNA: organic
  • Phosphorus: inorganic

Human Impact:

  • Commercial fertilizer- runoff goes into lakes, rivers, and ocean


  • "Carbon Cycle." Carbon Cycle. N.p., n.d. Web. 16 Mar. 2017.
  • "The Carbon Cycle." The Carbon Cycle. Windows to the Universe, n.d. Web. 15 Mar. 2017.
  • "Chemical Reactions in the Nitrogen Cycle - Knightrogen Cycle." Google Sites. N.p., n.d. Web. 16 Mar. 2017.
  • Gornitz, Vivien. "Human Impacts on the Global Water Cycle." NASA. NASA, Mar. 1997. Web. 14 Mar. 2017.
  • Harrison, Ph.D. John Arthur. "" Visionlearning. Visionlearning, Inc., 11 Feb. 2017. Web. 16 Mar. 2017.
  • "Phosphorus Cycle." The Environmental Literacy Council. The Environmental Literacy Council, n.d. Web. 16 Mar. 2017.
  • Sea Turtle Underwater with Fish. Digital image. James Cook University, 17 Aug. 2016. Web. 14 Mar. 2017.
  • "The Water Cycle.", n.d. Web. 14 Mar. 2017.


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