Summary
Respiration in plants is the cellular process of breaking down organic molecules through oxidation to release energy, which is then captured in ATP molecules for use in life processes. All living organisms, including plants, require this process to obtain the energy needed for growth, reproduction, and other vital functions.
Respiration in plants involves the breakdown of food molecules (primarily glucose) through a series of enzyme-controlled reactions in the cytoplasm and mitochondria. The process occurs in stages: glycolysis (partial breakdown in cytoplasm), fermentation (under anaerobic conditions), and aerobic respiration (complete oxidation via Krebs' cycle and electron transport system in mitochondria). Plants lack specialized respiratory organs but exchange gases through stomata and lenticels. The energy released during oxidation is not used directly but is trapped in ATP molecules, which act as the cell's energy currency. Unlike photosynthesis which stores solar energy in chemical bonds, respiration releases this stored energy for cellular processes.
Key points & formulas
- 01Respiration is the oxidative breakdown of organic molecules to release energy, occurring in cytoplasm and mitochondria; glucose is the primary respiratory substrate
- 02Glycolysis occurs in the cytoplasm and breaks one glucose molecule into two pyruvic acid molecules with net gain of 2 ATP
- 03Aerobic respiration (Krebs' cycle and electron transport system) completely oxidizes pyruvate to CO₂ and H₂O, yielding approximately 38 ATP per glucose molecule
- 04Fermentation occurs under anaerobic conditions and produces either lactic acid or ethanol with less than 7% energy release compared to aerobic respiration
- 05The electron transport system (ETS) on the inner mitochondrial membrane uses oxygen as the final electron acceptor, driving ATP synthesis through oxidative phosphorylation
- 06Respiration is an amphibolic pathway involved in both catabolism (breakdown) and anabolism (synthesis) of fats, proteins, and carbohydrates
Frequently asked questions
01Do plants breathe like animals?
Yes, plants require O₂ for respiration and release CO₂. However, unlike animals, plants have no specialized respiratory organs. Instead, they use stomata (in leaves) and lenticels (in stems) for gaseous exchange. Each plant part takes care of its own gas-exchange needs, and plants have lower respiratory rates than animals.
02What is the difference between glycolysis and aerobic respiration?
Glycolysis is the initial stage occurring in the cytoplasm where one glucose molecule is broken down into two pyruvic acid molecules with a net gain of 2 ATP. Aerobic respiration includes the Krebs' cycle and electron transport system in the mitochondria, which completely oxidize pyruvate to CO₂ and H₂O, yielding approximately 38 ATP per glucose molecule. Aerobic respiration requires oxygen, while glycolysis does not.
03Why is ATP important in respiration?
ATP (adenosine triphosphate) is the energy currency of the cell. Energy released during oxidation in respiration cannot be used directly; instead, it is trapped in ATP molecules. These ATP molecules are then broken down whenever and wherever energy is needed for cellular processes like absorption, transport, movement, and reproduction.
04Is the NCERT Class 11 Biology Chapter 12 PDF free to download?
Yes, NCERT textbooks including the Class 11 Biology Chapter 12 PDF are free to download. They are published by the National Council of Educational Research and Training and are made available as public educational resources.
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