Microbial carbon cycle

48 important questions on Microbial carbon cycle

What are different ways carbon can be emitted?

Human activities, respiration, photosynthesis and CO2 dissolution

What is carbon respiration?

A process in which living organisms convert organic carbon compounds into carbon dioxide

What happens in the process of carbon respiration?

Energy is released
  • Higher grades + faster learning
  • Never study anything twice
  • 100% sure, 100% understanding
Discover Study Smart

What is the main purpose of carbon respiration?

To conserve energy by oxidizing reduced carbon substrates and converting the released free energy into ATP

What are the reductants generated in carbon respiration used for?

For biosynthesis or they are re-oxidized via respiration to maintain the redox balance and generate ATP

What is the first step of the citric acid cycle?

Acetyl-CoA and oxaloacetate are condensed to citrate

What is the second step of the citric acid cycle?

Stepwise oxidation of pyruvate

What does the second step of the citric acid cycle yield?

2 CO2, 3 NADH, 1 FADH2 and 1 ATP per pyruvate

How can another citric acid cycle start?

Citrate is converted back to oxaloacetate

How is redox balance achieved?

Through respiration

What are the key enzymes in aerobic respiration?

NADH dehydrogenase, succinate dehydrogenase, cytochrome bc complex and cytochrome aa3 oxidase

How do electrons enter the aerobic respiration chain?

From a primary donor at either Complex I or Complex II

How do electrons exit the aerobic respiration chain?

By reducing the terminal electron acceptor (O2)

What can the proton motor force released by aerobic respiration be used for?

It can be used by ATP synthesis to generate ATP

What is carbon fixation?

A process by which living organisms convert inorganic carbon (particularly CO2) to organic compounds

How is carbon fixation powered and what is the electron source?

It is powered by ATP and NAD(P)H provides the electrons

What does the energy source provide in carbon fixation?

Free energy to drive thermodynamically unfavourable reactions, fuels bond formation and metabolism and “does work”

What does the electron source provide in carbon fixation?

Electrons, reduces CO2 and other oxidized intermediates and supplies chemical reducing equivalents

Into what two categories can aquatic prokaryote dominated photosynthesis be divided?

Phototrophic purple and green bacteria and cyanobacteria

What is the difference between the two categories of aquatic prokaryote dominated photosynthesis?

The phototrophic bacteria use the anoxygenic cycle and the cyanobacteria use the oxygenic cycle

What are the similarities between phototrophic bacteria and cyanobacteria?

Both use light as the energy source, make ATP from ADP and fix CO2 into organic carbon

What are the differences between phototrophic bacteria and cyanobacteria?

Cyanobacteria use H2S as an electron donor instead of water, this means there is no O2 produced

What are the three most important biological pathways for carbon fixation?

Calvin cycle, rTCA cycle and reductive acetyl-CoA

What is the difference between energy source and reducing power?


Reducing power is reducing electric energy and energy source provides electrons and reduces CO2 and other oxidized intermediates

What does the Calvin cycle require?

6 ribulose bisphosphate and 6 CO2

What does the Calvin cycle produce?

6 molecules of ribulose 5-phosphate + one hexose (6 carbons)

What is the key enzyme in the Calvin cycle?

RuBisCo (Ribulose-1,5-bisphosphate Carboxylase/Oxygenase)

What three major steps does the Calvin cycle include?

Carboxylation, reduction and regeneration

How ATPs does the Calvin cycle require?

18 ATP

Why is the rTCA cycle more efficient than the Calvin cycle?

It requires 24 protons, but only 10 ATP to fix 6 CO2

What is the key enzyme of acetogenesis?

Carbon monoxide dehydrogenase

What is electron bifurcation?

A system that uses the favourable step to power the unfavourable one

What is acetate for heterotrophic organisms?

An electron donor

How is ATP generated in fermentation?

Substrate-level phosphorylation

How is ATP generated in respiration?

Oxidative phosporylation

What are primary fermenters?

Bacteria that initiate fermentation by breaking down complex organic compounds such as carbohydrates, proteins, and lipids

What does primary fermentation result in?

Volatile fatty acids (VFAs), alcohols, hydrogen (H₂), carbon dioxide (CO₂), and organic acids

What are secondary fermenters?

Bacteria that use products generated by primary fermenters as substrates and ferment these into even smaller molecules

What does secondary fermentation result in?

Acetate, hydrogen, CO₂

What is anaerobic sludge digestor?

A method that can be used for the stabilization of obtained sludge and biosolids under anaerobic conditions

What is anaerobic sludge digestor known for?

Achieving renewable energy and produce biogas from waste and sludge

What are the tree main types of methanogensis?

Hydrogenotrophic, acetoclastic and methylotrophic

Which two types of methanogenesis conserve energy via electron transport phosphorylation

Acetoclastic and methylotrophic

What is the key enzyme in methanogenesis?

Methyl coenzyme M reductase (MCR)

How can methanotrophy occur under both aerobic and anaerobic conditions?

Since they can use a wide range of electron acceptors

What are the steps of methane oxidation?

First methane into alcohol, then into formaldehyde, then into formic acid and lastly into CO2

What is the key enzyme of methane oxidation?

Methane monooxygenase

How can anaerobic oxidation of methane occur?

Reverse and modified methanogenesis pathway

The question on the page originate from the summary of the following study material:

  • A unique study and practice tool
  • Never study anything twice again
  • Get the grades you hope for
  • 100% sure, 100% understanding
Remember faster, study better. Scientifically proven.
Trustpilot Logo