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LECTURE 19. THE CARBON CYCLE

I. Introduction to Biogeochemical Cycles

Nature recycles. The atoms within organisms (C, H, O, N, S, Fe, traces of other metals) came from inorganic, non-living matter. The same atoms will exit living organisms as inorganic matter, thus completing a cycle. Microorganisms are crucial to this recycling.

A. Some Important Implications and Observations

II. Introduction to the Carbon Cycle

Most of the carbon within organisms comes from the carbon dioxide (CO2) in the air.The atmosphere is 0.03 mol % in CO2. However, the greatest physical reservoir of carbon is not atmospheric carbon dioxide but instead is located in the Earth's crust and is not easily accessible to biological organisms. Figures 17.27 and 17.28 show the reservoirs of carbon and the transactions that take place in the carbon cycle.

A. What Reactions Involving the Carbon Cycle Must Balance in Nature?

B. Some Imbalances in the Carbon Cycle Caused by H. sapiens

III. Details of the Carbon Cycle

A. Overview of Carbon Fixation (see the handout)

Carbon fixation involves the incorporation ("fixation") of carbon from carbon dioxide into organic molecules and its subsequent reduction to the level of an alcohol.

B. Requirements for Carbon Fixation

C. The Calvin Cycle (consult the handout, Figures 16.19 and16.20)

D. Aerobic Degradation of Carbon

E. Anaerobic Degradation of Carbon

Anaerobic degradation of carbon is strictly done by microorganisms. This is responsible for most of the biological CO2 and CH4 released to the atmosphere.