This document discusses different types of anaerobic respiration. It explains that anaerobic respiration uses inorganic molecules other than oxygen as the final electron acceptor, such as sulfur, nitrate, carbon dioxide or metals. It provides examples of denitrification and sulfate reduction, two types of anaerobic respiration where nitrate and sulfate are used as electron acceptors. The document also notes that anaerobic respiration produces less energy than aerobic respiration due to fewer protons being pumped out during electron transport.

1. ANAEROBIC RESPIRATION

2. Aerobic Respiration Overview
• carbon flows to carbon dioxide
• electrons flow to external acceptor
• energy produced by oxidative phosphorylation
through PMF

3. Respiration of Glucose
glucose
pyruvate
Citric
Acid
Cycle
Electron Transport System
CO2
e-
½ O2
H20
glycolysis
Electrons flow in the form of
reduced dinucleotides (NADH
and FADH)
ADP
ATP
GDP
GTP

4. 4
Oxidation Without O2
1. Anaerobic respiration
– Use of inorganic molecules (other than O2) as
final electron acceptor
– Many prokaryotes use sulfur, nitrate, carbon
dioxide or even inorganic metals
2. Fermentation
– Use of organic molecules as final electron
acceptor

5. Anaerobic Respiration
• Some bacteria are capable of aerobic
respiration and anaerobic respiration (aerobic
is preferred due to more favorable energy
production)
• Other bacteria that carry out anaerobic
respiration are obligate anaerobes
• In either case, the electron acceptor chosen is
based on maximizing free energy production
for cell growth

6. Anaerobic (Anoxic) Respiration of
Organics
• Organic compounds are most often the
original electron donor
• Most electron acceptors are inorganic.
• Electron transport systems in anaerobic
respiration is similar to that of aerobic
metabolism

7. Nitrate Reduction
(Denitrification)
• Conversion of nitrate (NO3
-
) as an electron acceptor
to ammonia (NH4
+) or nitrate (NO2
-
)
• Nitrite undergoes further reduction to produce nitric
oxide (NO), nitrous oxide (N2O), and nitrogen gas
(N2), all of which are lost to the atmosphere
• Denitrification results in a loss of nitrogen from
ecosystems and is only carried out biologically by
bacteria
• Nitrogen removal treatment processes incorporate
denitrification

8. Aerobic Respiration and Denitrification
• During aerobic
respiration, three
areas where H+ is
pumped out to
establish PMF

9. Denitrification
• Only two areas in
ETC that pump
out H+ as
compared to
three for aerobic
respiration
• Less energy
generated

10. Respiration and Anaerobic Respiration (E. coli)
Figure 21.14a

11. Respiration and Anaerobic Respiration (P. stutzeri)
Figure 21.14c
Periplasmic
proteins

12. Sulfate Reduction
• sulfate (SO4)reduction to sulfide (S2-)requires eight
electrons
• the first intermediate in this process is the
production of sulfite (SO3
2-) and requires two
electrons
• conversion of sulfite to sulfide requires an additional
six electrons

13. Sulfate Dissimilatory Reduction

14. Electron Transport and Energy Conservation during Sulfate Reduction
Figure 21.16
Membrane-associated
propotein complex