Class 9 Biology Chapter 12 Respiration in Plants: 13 Solved Previous Year Questions (2020–2025)

Respiration in plants is the process by which plant cells break down organic molecules (glucose) to release energy in the form of ATP. Unlike photosynthesis, respiration occurs in all plant cells—roots, stems, and leaves—24/7. NCERT Class 9 Chapter 12 emphasizes that plants perform both aerobic respiration (with oxygen) and anaerobic respiration (without oxygen). The mitochondria is the powerhouse where aerobic respiration occurs, producing approximately 38 ATP molecules per glucose molecule. Understanding this process is vital for board exams as it frequently appears in 2-mark, 3-mark, and 5-mark questions.

Aerobic respiration in plants follows three main stages: glycolysis, Krebs cycle (citric acid cycle), and electron transport chain. Glycolysis occurs in the cytoplasm and breaks one glucose molecule into two pyruvate molecules, yielding 2 ATP and 2 NADH. The Krebs cycle takes place in the mitochondrial matrix, further oxidizing pyruvate and generating CO₂, ATP, NADH, and FADH₂. Finally, the electron transport chain in the inner mitochondrial membrane uses NADH and FADH₂ to produce the majority of ATP. Previous year questions often ask students to identify where each stage occurs and calculate energy yield—essential for scoring high marks in board exams.

Anaerobic respiration occurs in plant cells when oxygen is unavailable, such as in waterlogged soil or during seed germination. In plants, anaerobic respiration typically results in fermentation, producing ethanol and CO₂ (alcoholic fermentation) or lactic acid (lactic acid fermentation). This process yields only 2 ATP per glucose molecule, far less than aerobic respiration. NCERT highlights that plant roots must have adequate oxygen; waterlogging can lead to root rot due to insufficient ATP production. CBSE board exams frequently ask students to compare aerobic and anaerobic respiration, making this a high-priority topic for last-minute revision.

Mitochondria are double-membrane organelles where the majority of ATP synthesis occurs during aerobic respiration. The outer membrane is permeable to small molecules, while the inner membrane contains the electron transport chain proteins and ATP synthase. The cristae (folds of the inner membrane) increase the surface area for biochemical reactions. In plants, mitochondria density varies by cell type—root cells and metabolically active cells have more mitochondria to meet energy demands. Understanding mitochondrial structure and function is critical for CBSE Class 9 exams, particularly for 5-mark questions that demand detailed explanations with labeled diagrams.

This section compiles authentic CBSE board exam questions spanning 2-mark, 3-mark, and 5-mark formats from 2020 to 2025. Questions include: 'Define aerobic respiration,' 'Compare aerobic and anaerobic respiration in a table,' 'Explain the role of mitochondria in ATP synthesis,' 'Why do plant roots require oxygen,' and 'Calculate the total ATP yield from one glucose molecule.' Each question includes a model answer aligned with NCERT textbook standards and marking schemes. Students can use these solved examples to identify question patterns, understand answer structure, and practice time management—all crucial for board exam success.

CBSETUTOR.ai has emerged as the leading 24x7 AI tutoring platform for CBSE students across India, trusted by lakhs of families. Our platform combines NCERT-aligned content with adaptive learning technology, offering instant doubt-solving for subjects like Biology, Chemistry, Math, and English. For Chapter 12 (Respiration in Plants), CBSETUTOR.ai provides video lessons, interactive quizzes, previous year question practice, and AI-powered explanations in Hindi and English. Students can access study materials anytime, anywhere—making exam preparation stress-free and effective. Whether you need clarification on anaerobic respiration or step-by-step solutions to board questions, CBSETUTOR.ai delivers personalized learning at scale.

CBSE examiners consistently test student understanding through specific question types: (1) Definition-based: 'What is aerobic respiration?' (2) Comparison: 'Differentiate between aerobic and anaerobic respiration.' (3) Diagram labeling: Identifying glycolysis, Krebs cycle, and electron transport chain. (4) Application: 'Why do germinating seeds respire faster?' (5) Calculation: 'How much ATP is produced during complete oxidation of one glucose?' (6) Concept-based: 'Explain why plants perform respiration 24/7 despite photosynthesizing during day.' Previous year analysis shows these patterns repeat across years, making them high-probability topics for your upcoming exam.

The complete oxidation of one glucose molecule through aerobic respiration yields approximately 30–32 ATP molecules in plant cells (compared to 36–38 in animal cells, due to differences in shuttle systems). Glycolysis produces 2 ATP, Krebs cycle produces 2 ATP, and the electron transport chain produces the remaining 26–28 ATP through chemiosmosis. CBSE exams frequently ask students to calculate total ATP yield and explain energy loss at each stage. Understanding the energetic efficiency of respiration—why only ~40% of glucose energy is captured as ATP—demonstrates deep knowledge valued by examiners. This concept often appears in 5-mark questions demanding detailed stepwise answers.

Plant respiration rate depends on multiple factors: temperature (enzymes work faster at optimal temperatures), oxygen availability (essential for aerobic respiration), light intensity, and the plant's metabolic demands. Root cells and rapidly dividing cells respire faster due to high ATP requirements. NCERT Chapter 12 emphasizes that respiration is temperature-sensitive; a 10°C rise can double respiration rate (Q₁₀ value). Germinating seeds show high respiration rates because they consume stored glucose for growth and development. CBSE board exams test this knowledge through scenario-based questions like 'Why do stored grains heat up during germination?' Understanding these factors helps students answer application-level questions that fetch higher marks.

Master Respiration in Plants with this exam-ready strategy: (1) Create a flowchart of all three respiration stages with location, inputs, and outputs. (2) Make a comparison table: Aerobic vs. Anaerobic, Photosynthesis vs. Respiration. (3) Solve all 13 previous year questions twice—first under timed conditions, then with NCERT reference. (4) Draw and label mitochondrial structure from memory. (5) Practice 5-mark answers using the NCERT answer format. (6) Use mnemonics for Krebs cycle intermediates (CITRIC ACID = Citrate, Isocitrate, α-Ketoglutarate, Succinyl-CoA, Succinate, Fumarate, Malate, Oxaloacetate). Consistent revision with these tools ensures you're board-exam-ready.