Metabolic interactions during photosynthetic and respiratory nitrogen assimilation in a green alga
Bibliographic record
Abstract
This chapter addresses some of the interactions that occur between primary nitrogen assimilation and photosynthetic and respiratory metabolism. Much of the pioneering work in this area was carried out by Syrett (Syrett, 1953, 1956 a,b , 1981) and Bassham, Kanazawa and co-workers (Bassham et al , 1981; Kanazawa et al , 1970, 1972, 1983). It is not coincidental that this work has often employed algal cells. Single-celled algae have C/N ratios between 7 and 12 compared with >20 in higher plants. Therefore, the relative importance of nitrogen in carbon metabolism of single-celled algae is much greater than in higher plants and the interactions between N assimilation and carbon metabolism are much more apparent. For several years our group has studied the interactions between photosynthesis, respiration and N assimilation in the green alga Selenastrum minutum . Our approach has been to grow this alga in chemostat cultures under N-limited conditions. The addition of a source of inorganic nitrogen (NH 4 + , NO 2 - or NO 3 - ) to these cells activates the assimilation of N into amino acids allowing study of the corresponding changes in metabolism. This chapter reviews some of the progress made using this system. Nitrogen assimilation by N-limited and N-sufficient algal cells The primary assimilation of inorganic N into amino acids and protein requires ATP, reducing power and carbon skeletons in the form of ketoacids. In photosynthetic tissues, ATP and reducing power are supplied by either photosynthetic or respiratory processes; however, most of the carbon skeletons used in amino acid synthesis are intermediates of respiratory metabolism (Fig. 1).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".