🌱 Biology : Chapter 2: Digestion and Transport of Nutrients

📘 Chapter Title: Breathing and Respiration

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🔍 Summary (150–250 words)

This chapter explains the essential biological processes of breathing and respiration, which provide energy for various life functions. It begins by distinguishing breathing (a mechanical process) from cellular respiration (a biochemical process). Breathing involves the inhalation and exhalation of air, while respiration refers to the release of energy from food molecules, especially glucose, inside cells.

The chapter outlines aerobic and anaerobic respiration, highlighting the role of oxygen in the former and its absence in the latter. Aerobic respiration releases more energy and occurs in mitochondria, whereas anaerobic respiration, seen in yeast and some muscle cells during fatigue, results in less energy and produces byproducts like alcohol or lactic acid.

In humans, the respiratory system consists of organs such as the nasal cavity, trachea, bronchi, lungs, and alveoli. These structures support gas exchange through a process called diffusion in the alveoli. The chapter also describes the mechanism of breathing, involving the diaphragm and intercostal muscles, and explains how breathing rate varies depending on physical activity.

Finally, it touches upon respiration in plants, showing how it occurs through stomata, lenticels, and root hairs, ensuring energy supply for cellular activities. The chapter effectively connects structure and function in both plants and animals, emphasizing the role of respiration in sustaining life.

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📌 Capsule Notes

🔹 Breathing vs Respiration

• Breathing: Physical process – inhaling O₂, exhaling CO₂.
  
  

• Respiration: Biochemical – breakdown of glucose to release energy (ATP).
  
  

• Takes place inside mitochondria in cells.
  
  

🔹 Types of Respiration

• Aerobic Respiration:
  
  

• Uses oxygen.
  
  

• Glucose + O₂ → CO₂ + H₂O + Energy.
  
  

• Occurs in most plants & animals.
  
  

• Anaerobic Respiration:
  
  

• No oxygen.
  
  

• Produces less energy.
  
  

• Byproducts:
  
  

• Yeast: Alcohol + CO₂.
  
  

• Muscles: Lactic acid.
  
  

🔹 Human Respiratory System

• Organs:
  
  

• Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli.
  
  

• Alveoli:
  
  

• Site of gas exchange.
  
  

• Surrounded by capillaries.
  
  

• O₂ diffuses into blood, CO₂ diffuses out.
  
  

🔹 Mechanism of Breathing

• Inhalation:
  
  

• Diaphragm contracts & moves down.
  
  

• Rib cage expands.
  
  

• Lungs fill with air.
  
  

• Exhalation:
  
  

• Diaphragm relaxes & moves up.
  
  

• Rib cage contracts.
  
  

• Air pushed out.
  
  

🔹 Breathing Rate

• Varies with activity level.
  
  

• Controlled by medulla in brain.
  
  

🔹 Respiration in Plants

• Occurs in all parts – leaves, roots, stems.
  
  

• Through:
  
  

• Stomata (leaves).
  
  

• Lenticels (stems).
  
  

• Root hairs (roots).
  
  

• Mitochondria perform cellular respiration.
  
  

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❓ Q&A – Questions with Answers

1. What is the difference between breathing and respiration?
   → Breathing is a physical process of air movement; respiration is a chemical process that releases energy from glucose.
   
   

2. Name the organelle where respiration takes place.
   → Mitochondria.
   
   

3. Write the word equation for aerobic respiration.
   → Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP).
   
   

4. What is anaerobic respiration? Give an example.
   → Respiration without oxygen. In yeast, it produces alcohol and CO₂.
   
   

5. Which part of the human respiratory system carries out gas exchange?
   → Alveoli.
   
   

6. What role does the diaphragm play in breathing?
   → It contracts during inhalation and relaxes during exhalation.
   
   

7. What is the breathing rate during rest in humans?
   → Around 12–20 breaths per minute.
   
   

8. Why do muscles feel tired after vigorous exercise?
   → Due to lactic acid accumulation from anaerobic respiration.
   
   

9. Mention any two differences between aerobic and anaerobic respiration.
   → Aerobic uses oxygen and yields more energy; anaerobic does not use oxygen and yields less energy.
   
   

10. How does gas exchange occur in plants?
    → Through stomata (leaves), lenticels (stems), and root hairs (roots).
    
    

11. What controls the rate of breathing in humans?
    → The medulla in the brain.
    
    

12. What happens to the rib cage during inhalation?
    → It expands outward and upward.
    
    

13. What are the end products of anaerobic respiration in muscles?
    → Lactic acid and a small amount of energy.
    
    

14. Which gas diffuses into the blood in the alveoli?
    → Oxygen.
    
    

15. Name the pathway of air during inhalation.
    → Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli.
    
    

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📚 Definitions & Key Terms

• Breathing: The movement of air in and out of the lungs.
  
  

• Respiration: The biochemical breakdown of food to release energy.
  
  

• Aerobic Respiration: Energy release with oxygen.
  
  

• Anaerobic Respiration: Energy release without oxygen.
  
  

• Alveoli: Air sacs in lungs for gas exchange.
  
  

• Diaphragm: Dome-shaped muscle aiding breathing.
  
  

• Lactic Acid: Product of anaerobic respiration in muscles.
  
  

• Stomata: Leaf pores for gas exchange.
  
  

• Lenticels: Small openings on stems for gaseous exchange.
  
  

• Root Hairs: Absorb water and gases from soil.
  
  

• ATP (Adenosine Triphosphate): Cellular energy currency.
  
  

• Mitochondria: Site of cellular respiration.
  
  

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🧠 Main Points for Revision

• Breathing ≠ Respiration.
  
  

• Aerobic = With oxygen, more energy.
  
  

• Anaerobic = No oxygen, less energy.
  
  

• Gas Exchange = In alveoli.
  
  

• Diaphragm = Inhalation & exhalation.
  
  

• Plants breathe through stomata, lenticels, roots.
  
  

• Mitochondria = Powerhouse of the cell.
  
  

• ATP = Energy form used by cells.
  
  

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📂 Topic-Wise Breakdown

1. Breathing vs Respiration

• Conceptual difference.
  
  

• Physical vs chemical process.
  
  

2. Types of Respiration

• Aerobic: Glucose + O₂ → CO₂ + H₂O + ATP.
  
  

• Anaerobic: Alcohol/lactic acid + less energy.
  
  

3. Human Respiratory System

• Pathway: Nose to alveoli.
  
  

• Structures and functions.
  
  

4. Mechanism of Breathing

• Inhalation: Diaphragm down, ribs expand.
  
  

• Exhalation: Diaphragm up, ribs contract.
  
  

5. Control of Breathing

• Medulla oblongata regulates rate.
  
  

6. Respiration in Plants

• Through stomata, lenticels, roots.
  
  

• Occurs in mitochondria.