What is CO 2 fixation ?

The reductive process associated with the assimilation of CO 2 . This pathway requires substantial amounts of energy from the cell in the form of ATP and reducing power.

Home / Summaries / Brock Biology of Microorganisms, Global Edition / co2-cycle-pathway

Metabolic Pathway of Microorganisms - Autotrophic Pathways

Q: What is the reverse citric acid cycle ( reductive TCA cycle )?

A pathway of CO 2 fixation. It requires 4 NADH, 2 reduced ferredoxins, and 10 ATP to synthesize 1 glucose from 6 CO 2 . Therefore it's more efficient than the Calvin cycle. Most of the reactions are catalyzed by reverse reactions of enzymes of the citric acid cycle, but it requires the activity of unique enzymes. Also, citrate synthase is replaced by citrate lyase , and succinate dehydrogenase by fumarate reductase .

Q: What is the 3-hydroxypropionate bi-cycle ?

A pathway of CO 2 fixation, where two CO 2 molecules are reduced to glyoxylate. It requires 16 ATP per glucose generated.

Q: What are 3-hydroxypropionate/4-hydroxybutyrate cyle , dicarboxylate/4-hydroxybutyrate cycle , and reductive acetylcoenzyme A pathway ?

These are all pathways of CO 2 fixation.

4 important questions on Metabolic Pathway of Microorganisms - Autotrophic Pathways

What is CO₂ fixation?

The reductive process associated with the assimilation of CO₂. This pathway requires substantial amounts of energy from the cell in the form of ATP and reducing power.

What is the reverse citric acid cycle (reductive TCA cycle)?

A pathway of CO₂ fixation. It requires 4 NADH, 2 reduced ferredoxins, and 10 ATP to synthesize 1 glucose from 6 CO₂. Therefore it's more efficient than the Calvin cycle. Most of the reactions are catalyzed by reverse reactions of enzymes of the citric acid cycle, but it requires the activity of unique enzymes. Also, citrate synthase is replaced by citrate lyase, and succinate dehydrogenase by fumarate reductase.