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
• Weathering of rocks adds phosphates (PO43-)
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