Which one of the following statements is correct ?

Glucose breakdown follows different pathways depending on the organism and oxygen availability. In aerobic respiration, which occurs in the presence of oxygen, glucose is completely oxidized into carbon dioxide (CO2), water (H2O), and a significant amount of energy [4]. This process is characteristic of all aerobic tissues [3]. In contrast, anaerobic pathways vary: in yeast (fermentation), glucose breaks down into ethanol and CO2 [2], while in human muscle cells during intense activity, it converts to lactic acid (lactate) due to oxygen deficiency [3]. Statement 1 is incorrect because not all organisms use aerobic pathways; some are obligate or facultative anaerobes. Statement 2 is incorrect as muscles produce lactate, not ethanol [3]. Statement 4 is incorrect because yeast produces ethanol and CO2, whereas lactate is the product of anaerobic respiration in animal muscles [1].

Sources

1. [2] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.5 > p. 88
2. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 10: Life Processes in Plants > 10.4 Do Plants Respire? > p. 149
3. [4] Science-Class VII . NCERT(Revised ed 2025) > Chapter 9: Life Processes in Animals > How does the exchange of gases happen? > p. 132
4. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.5 > p. 87