proton motive force
- drives protons across the membrane
- stores energy to make ATP and do other cellular work
- The transfer of H+ through a proton pump generates an electrochemical gradient of protons
- drives the conversion of ADP to ATP throughATP synthase.
- This process is known as chemiosmosis
organotrophy
- chemoorganotrophy
- organic electron donors
- involves organic electron donors and inorganic or organic terminal electron acceptors
lithotrophy
- chemolithotrophy
- inorganic electron donors
- involves inorganic electron donors and inorganic or organic terminal acceptors
phototrophy
- light absorption excites electrons
- involves light capture by chlorophyll, usually coupled to splitting of H2S or H2O or organic molecules
Electron Transport Systems
- Or electron transport chain (ETC)
- energy-yielding reactions involve transfer of electrons from a reduced electron donor to an oxidized electron acceptor
Energy Storage
- In redox reactions, the DG values are proportional to the reduction potential (E) between the oxidized form (e– acceptor) and its reduced form (e– donor)
- reaction is favored by positive values of E, which yield negative values of DG
F1Fo ATP Synthase
-a highly conserved protein complex, made of two parts
Obligate aerobes
organisms that grow using only O2 as a terminal electron acceptor
anaerobic respiration
- occurs in environments where oxygen is scarce
- unique to prokaryotes.
- usually possess alternative electron donors and electron acceptors
dissimilatory metal reduction
-important class of anaerobic respiration involves the reduction of metal cations
-metals most commonly reduced are:
Iron (Fe3+ → Fe2+)
Manganese (Mn4+ → Mn2+)
Methanogenesis
- reduction of CO2 and other single-carbon compounds to methane.
- Performed only by archaea called methanogens
methanotrophs
Prokaryotes that oxidize methane with a terminal electron acceptor such as O2, nitrate, or sulfate
