FERMENTATION Example On the left side glucose is

FERMENTATION: Example: On the left side, glucose is oxidized to pyruvate. On the right side, pyruvate can be reduced to acids, alcohols and gases.

RESPIRATION: ANAEROBIC RESPIRATION employs an electron acceptor other than O 2 such as nitrate (NO 3–) which is reduced to nitrite (NO 2–) or N 2.

PHOTOTROPHS also oxidize chemical compounds, but the ultimate source of energy is light. "Phototrophy" is shown here as the set of light-dependant, catabolic reactions associated with photosynthesis (the other reactions of which are anabolic). PHOTOTROPHY: ("chl" represents chlorophyll. ) Phototrophy can be OXYGENIC (evolving O 2 when H 2 O serves as the electron donor) or ANOXYGENIC (non-O 2 evolving).

Mechanisms of energy release: overview 1. Fermentation -- oxidation of an organic compound in the absence of external electron acceptor (no oxygen required). Uses SLP (substrate-level phosphorylation) 2. Respiration -- oxidation of an organic compound where oxygen is the final electron acceptor. Uses ETS (electron transport system) as well as SLP 3. Anaerobic respiration (unique to bacteria) -- oxidation of organic compounds where an external substrate other than oxygen serves as final electron acceptor. Exs: nitrate, sulfate, carbon dioxide