# Respiration in Plants Notes, Class 11 Biology | SwaVid Respiration in Plants, NCERT Class 11 Biology: notes with key ideas, key terms, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/biology/chapter/respiration-in-plants Source: https://www.swavid.com/cbse/class-11/biology/chapter/respiration-in-plants # Respiration in Plants ## Key terms ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Biology on SwaVid ### Cellular respiration and substrates ### Glycolysis ### Fermentation ### Tricarboxylic acid cycle ### Electron transport system and phosphorylation ### Amphibolic pathway and respiratory quotient ### Next chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Biology › Respiration in Plants Notes written by SwaVid from the NCERT textbook. Class 11 Biology, Chapter 12. Key ideas, formulas and common mistakes. CBSE prints 12 marks for Unit IV, not for this chapter alone. Short answer. This chapter explains cellular respiration, the mechanism by which plants break down respiratory substrates to release energy for ATP synthesis. Students learn the biochemical stages of glycolysis, fermentation, the citric acid cycle, electron transport system, and respiratory quotients. Source: NCERT Biology (Reprint 2026-27) , Chapter 12, Respiration in Plants Respiration is the mechanism of breaking of the C-C bonds of complex compounds through oxidation within cells, leading to release of energy. Compounds that are oxidised during this process are called respiratory substrates, with carbohydrates being the most common. Glycolysis occurs in the cytoplasm of all living cells and is an anaerobic process. A single molecule of glucose is broken down into two molecules of pyruvic acid through a sequence of ten enzyme-catalysed steps, yielding a net gain of 2 ATP and 2 NADH. In anaerobic conditions, pyruvic acid is converted to lactic acid, or to ethanol and carbon dioxide. Yeast cells carry out alcoholic fermentation using enzymes pyruvic acid decarboxylase and alcohol dehydrogenase, which becomes toxic to yeast when alcohol reaches about 13 percent. Pyruvate enters the mitochondrial matrix and undergoes oxidative decarboxylation to form acetyl CoA. Acetyl CoA enters the TCA cycle by combining with oxaloacetic acid to form citric acid. Subsequent steps in the cycle release carbon dioxide, NADH, FADH₂, and GTP. Electrons from NADH and FADH₂ pass through complex I to IV in the inner mitochondrial membrane to reach oxygen, the terminal electron acceptor. This electron flow pumps protons into the intermembrane space, creating a gradient that drives ATP synthesis through complex V (ATP synthase). Respiration involves both catabolic breakdown of substrates and anabolic withdrawal of intermediates for synthesis, making it an amphibolic pathway. The respiratory quotient is the ratio of the volume of CO₂ evolved to the volume of O₂ consumed during respiration. Try each question first. Then tap it to see the answer. RQ = (Volume of CO₂ evolved) / (Volume of O₂ consumed) RQ = 102 / 145 RQ = 0.7 0.7 Total ATP formed by substrate-level phosphorylation is 4, but 2 ATP are consumed in early steps. Net ATP gained = 4 - 2 = 2 ATP. In the oxidation of PGAL, 2 molecules of NADH + H⁺ are generated. 2 ATP and 2 NADH Oxidation of 1 molecule of NADH yields 3 molecules of ATP via ETS. Number of ATP = 10 × 3 = 30 ATP. 30 ATP Plant Growth and Development . Photosynthesis in Higher Plants . The 19 chapters of Class 11 Biology . CBSE does not give marks to one chapter. It prints 12 marks for Unit IV, Plant Physiology, which includes Respiration in Plants. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Plant Growth and Development. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 12 NCERT book - 12 marks, Unit IV - 3 quick checks - Believing that plants do not breathe or respire . Plants do not have specialised organs like lungs, but every living plant cell respires using stomata and lenticels for diffusion of gases. - Confusing the site of glycolysis with the mitochondrial matrix . Glycolysis occurs solely in the cytoplasm of the cell. Only the aerobic fate of pyruvate occurs inside the mitochondria. - Counting 2 ATP per NADH instead of 3 ATP in ETS . Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, whereas one molecule of FADH₂ produces 2 molecules of ATP. - Assuming respiratory quotient is always 1 . RQ is 1.0 only for carbohydrates. Fats give an RQ of about 0.7, and proteins give an RQ of about 0.9. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 11](https://www.swavid.com/cbse/class-11) - [Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup) - [All 19 chapters](https://www.swavid.com/cbse/class-11/biology/chapters) - [NCERT Biology (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/plant-growth-and-development) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/photosynthesis-in-higher-plants) - [Class 11 Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup)