Chemoheterotrophy

Question 1

What is fermentation

Answer 1

• a type of chemoheterotrophy
• Anaerobic
• no need for external TEA
• end products still have usable energy (alcohol)
• glucose –> alcohol + CO2

Question 2

What is respiration?

Answer 2

• can be aerobic or anaerobic

- the production of energy

Question 3

Describe aerobic chemoheterotrophy

Answer 3

• aka respiration
• glucose is catabolism, releasing carbon dioxide and water as the bi products, to derive energy
  C6H12O6 + 6O2 –> ^COO2 + H2O
• organic C is oxidised (by O2), forming CO2
• oxygen is reduced (by organic C) forming H2O
• produces more energy than fermentation

Question 4

Why is respiration better than fermentation?

Answer 4

• yields more energy per oxidised substrate than fermentation
• has a greater different in electrode potential between the PED and TEA, so more redox reactions, conserves heat and more energy produced

Question 5

Why is fermentation better than respiration?

Answer 5

• fermentation products still have energy that is able to be derived
• fermentation does not need an external TEA so does not depend on microbes environmental conditions as much

Question 6

List the forms of anaerobic chemoheterotrophy (from most to least thermodynamically favourable)

Answer 6

• diss. nitrate reduction
• diss. manganese reduction
• diss. iron reduction
• diss. reduction of other metals and metalloids
• diss. sulfate reduction
• methanogenesis

PED is organic C
TEA is NOT O2
Need a species in its oxidised form that can accept electrons and become reduced

Question 7

where do dissimilatory reduction happen?

Answer 7

In the cell membrane

Question 8

What is dissimilatory nitrate reduction

Answer 8

• most energetically favourable
• PED = organic C
• TEA = nitrate (NO3-)
• important in soils and freshwater subject too agricultural pollution or sewage
• denitrification: NO3- –> NO2- –> NO –> N2O –> N2
• not all denitrifying bacteria reduce NO3- completely to N2
• nitrate ammonification: NO3- –> NO2- –> NH3