Biogeochemical Cycles

Essential Knowledge Objectives 2.A.3 (a) Biogeochemical Cycles

• Cycle inorganic and organic nutrients between organisms and the environment – Carbon cycle – Nitrogen cycle – Phosphorus cycle – Water cycle (also known as the hydrological cycle)

Cycling of Matter

• Organisms must exchange matter with the environment to grow, reproduce and maintain organization • Molecules and atoms from the environment are necessary to build new molecules Molecules Essential for Life

• Carbohydrates – composed of C, H, and O, monomer is a monosaccharide • Lipids – composed of C, H, and O, monomers are fatty acids and glycerol • Proteins – composed of C, H, O, N, and S in trace amounts, monomers are amino acids • Nucleic Acids – composed of C, H, O, N and P, monomers are nucleotides Carbon

• Carbon moves from the environment to organisms where it is used to build the essential organic molecules

• Carbon is used in storage compounds and cell formation in all organisms Carbon in the Environment

• Carbon found in something non-living is called inorganic carbon • Inorganic carbon is found in rocks (limestone), shells, the atmosphere and the oceans • Living organisms must “fix” inorganic carbon into organic carbon to build the organic compounds necessary for life Carbon Cycle Nitrogen and Phosphorus • Nitrogen moves from the environment to organisms where it is used to build proteins and nucleic acids

• Phosphorus moves from the environment to organisms where it is used to build nucleic acids, certain lipids, and ATP (cell energy) Nitrogen in the Environment • The main reservoir for inorganic nitrogen is the

atmosphere – 80% nitrogen gas (N2) • During nitrogen fixation, bacteria (and other processes) fix inorganic nitrogen into forms that can be used by living organisms to synthesize organic compounds

Nitrogen Cycle Phosphorus in the Environment • Most inorganic phosphorus in found in sedimentary rock of marine origin • Phosphorus is also found in soil and dissolved in the oceans 3- • Weathering of rocks adds phosphates (PO4 ) to the soil which plants can absorb Phosphorus Cycle Water • Living systems depend on the properties of water that result from its polarity and hydrogen bonding • Living organisms are mostly made of water (think cytoplasm and extracellular fluids!) • Universal solvent supports cell reactions • Acts as a delivery system between cells Water Cycle (Hydrologic) Water Cycle