NCERT Class 11 Biology Biology: Chapter 12 — Respiration in Plants
This chapter, 'Respiration in Plants,' from NCERT Class 11 Biology, delves into the fundamental process of cellular respiration. It explains that all living organisms, including plants and microbes, require energy for life activities, obtained by oxidizing food molecules. While green plants produce their own food through photosynthesis, non-green parts and animals obtain it from external sources. The chapter details how this energy is released through the breakdown of complex compounds in a step-wise, enzyme-controlled process, primarily in the cytoplasm and mitochondria. This released energy is not used directly but is trapped in ATP, the cell's energy currency. It also touches upon plants having stomata and lenticels for gaseous exchange, unlike animals' specialized organs, and how different plant parts manage their own gas exchange needs due to lower respiration rates. The chapter sets the stage for understanding the mechanisms of energy release and its utilization in biological systems, crucial for CBSE learning.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 11 |
| Subject | Biology |
| Book | Biology |
| Chapter | Chapter 12 — Respiration in Plants |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 770 |
Learning outcomes
- Understand the necessity of energy for life processes in all organisms.
- Differentiate between photosynthesis and respiration.
- Explain the role of ATP as the energy currency of the cell.
- Identify the sites of respiration in eukaryotic cells.
- Recognize the mechanisms of gaseous exchange in plants.
Vocabulary
| Word | Meaning |
|---|---|
| Respiration | The breaking of C-C bonds of complex compounds through oxidation within cells, leading to energy release. |
| Respiratory Substrates | Compounds that are oxidized during respiration to release energy. |
| ATP | Adenosine triphosphate; the energy currency of the cell. |
| Photosynthesis | The process by which green plants and cyanobacteria use light energy to synthesize food. |
| Stomata | Pores on the surface of leaves and stems for gaseous exchange. |
| Lenticels | Pores in the bark of woody stems and roots for gaseous exchange. |
| Glycolysis | The initial pathway of cellular respiration. |
| Aerobic Respiration | Respiration that occurs in the presence of oxygen. |
| Fermentation | An anaerobic process that releases energy from organic molecules. |
| Heterotrophic | Organisms that obtain food from external sources. |
| Saprophytes | Organisms that feed on dead and decaying matter. |
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Practice questions
- Why is energy essential for life processes? Answer: Energy is essential for all life activities such as absorption, transport, movement, reproduction, and breathing.
- What is the primary source of energy for most life on Earth? Answer: Ultimately, all the food respired for life processes comes from photosynthesis.
- What is respiration? Answer: Respiration is the breaking of C-C bonds of complex compounds through oxidation within cells, leading to the release of energy.
- What is the role of ATP in a cell? Answer: ATP acts as the energy currency of the cell, storing energy released from respiration to be used for various cellular activities.
- Do plants have specialized organs for gaseous exchange like animals? Answer: No, plants do not have specialized respiratory organs; they use stomata and lenticels for gaseous exchange.
Frequently asked questions
Do plants breathe?
Yes, plants require O2 for respiration and give out CO2, similar to animals, though they lack specialized respiratory organs.
Where does the energy for life processes come from?
Energy is obtained by the oxidation of food macromolecules, which ultimately originates from photosynthesis.
What are respiratory substrates?
Respiratory substrates are compounds like carbohydrates, proteins, fats, or organic acids that are oxidized within cells to release energy.
How is energy released during respiration used?
The energy released is not used directly but is trapped in the synthesis of ATP, which then provides energy for cellular activities.
How do plants perform gaseous exchange without specialized organs?
Plants use stomata (on leaves and stems) and lenticels (on woody parts) for gaseous exchange, as their respiration rates are generally lower than animals'.
Are all parts of a green plant photosynthetic?
No, only cells containing chloroplasts, typically in superficial layers, perform photosynthesis. Other non-green parts need food for respiration.
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NCERT Class 11 Biology — Biology — Chapter 12 — Respiration in Plants. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.