Agricultural Applications

• Seed storage and viability: Respiration rate determines seed longevity. Cold temperatures and reduced $O_{2}$ (controlled atmosphere storage) slow aerobic respiration, extending seed and grain shelf life and reducing dry weight loss.
• Germination monitoring via RQ: Seeds germinating from fat reserves show RQ < 1 (≈ 0.7) initially, rising toward 1.0 as carbohydrate reserves take over. RQ monitoring is used to assess germination progress and storage conditions.
• Post-harvest storage of fruits and vegetables: Controlled atmosphere (high C$O_{2}$, low $O_{2}$) slows aerobic respiration, reducing heat generation and extending shelf life. Climacteric fruits (e.g., apple, mango) show a respiratory climax before ripening.
• Waterlogged soil and root suffocation: $O_{2}$ depletion in waterlogged soils forces root cells into anaerobic respiration. Ethanol and lactate accumulate, which are toxic to cells, causing root death and crop loss (e.g., paddy fields vs upland crops).
• CAM plants in arid agriculture: Night C$O_{2}$ fixation into malic acid (RQ → ∞) allows stomata to close during the day, reducing water loss. Used in xerophyte cultivation strategies for drought-resistant agriculture.
• Industrial fermentation (Saccharomyces): Yeast alcoholic fermentation is the basis of bread making (C$O_{2}$ leavens dough), beer and wine production (ethanol), and biofuel (bioethanol) generation from agricultural waste.
• Yoghurt and cheese production (Lactobacillus): Lactic acid fermentation acidifies milk, preserving it and creating dairy products. Industrial use of lactate dehydrogenase activity from bacterial cultures.

Medical/Clinical Applications

• Beriberi disease: Deficiency of thiamine (Vitamin $B_{1}$) impairs TPP — a required cofactor for pyruvate dehydrogenase complex. Pyruvate accumulates, causing neurological damage (dry Beriberi) or cardiovascular failure (wet Beriberi).
• Lactic acidosis: Excessive anaerobic respiration (during strenuous exercise, circulatory shock, or tissue hypoxia) causes lactate accumulation, dropping blood pH and causing muscle fatigue and metabolic acidosis.
• Indirect calorimetry (RQ in nutrition): Measuring a patient's RQ helps clinicians determine which substrate they are oxidising — a dietary RQ of 0.7 indicates fat-burning (favoured in ketogenic diets for obesity), while RQ = 1.0 suggests carbohydrate metabolism.
• Cyanide and CO poisoning: Cyanide inhibits Complex IV (cytochrome c oxidase); CO competes with $O_{2}$ at the same site. Both halt the ETS, stop chemiosmosis, and cause rapid ATP depletion and cell death despite adequate $O_{2}$ availability (for cyanide) or glucose supply.