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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