Respiration in Plants Class 11 NCERT PDF: Complete Guide & Notes

What Is Respiration in Plants? Definition and Importance

Respiration in plants is a biochemical process where glucose is broken down to release energy. Unlike photosynthesis, which stores energy, respiration releases it for the plant’s metabolic activities.

Key points:

• Occurs in all living plant cells
• Converts glucose and oxygen into carbon dioxide, water, and energy
• Energy is stored as ATP (adenosine triphosphate)

This energy powers growth, repair, and other vital functions. Understanding respiration is essential for Class 11 students to grasp plant physiology basics.

Types of Respiration in Plants: Aerobic vs Anaerobic

Plants perform two main types of respiration:

1. Aerobic Respiration

• Requires oxygen
• Produces carbon dioxide, water, and energy
• Equation: $$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{energy}$$

2. Anaerobic Respiration

• Occurs without oxygen
• Produces ethanol or lactic acid and less energy
• Example: Fermentation in roots under waterlogged conditions

Class 11 NCERT students should focus on these differences for exams.

Respiratory Substrates: What Do Plants Use for Energy?

Respiratory substrates are molecules broken down to release energy during respiration. In plants, these include:

• Carbohydrates: Mainly glucose, the primary substrate
• Fats: Broken down into glycerol and fatty acids
• Proteins: Used only when carbohydrates and fats are unavailable

Glucose is the most common substrate, entering glycolysis to start the respiration process. Understanding substrates helps Class 11 students link nutrition and energy production.

Stages of Respiration in Plants Explained

Respiration in plants occurs in three main stages:

1. Glycolysis

• Takes place in the cytoplasm
• Glucose (6-carbon) splits into two molecules of pyruvate (3-carbon)
• Produces 2 ATP and 2 NADH molecules

2. Krebs Cycle (Citric Acid Cycle)

• Occurs in mitochondria
• Pyruvate is converted to Acetyl-CoA, entering the cycle
• Produces CO2, NADH, FADH2, and 2 ATP molecules

3. Electron Transport Chain (ETC)

• Located in mitochondrial inner membrane
• NADH and FADH2 donate electrons
• Energy released pumps protons, producing 32-34 ATP molecules

Overall ATP yield: Approximately 36-38 ATP per glucose molecule

This detailed understanding is crucial for Class 11 students to master respiration.

How to Download Respiration in Plants Class 11 NCERT PDF

Students can download the official NCERT PDF for respiration in plants Class 11 from the NCERT website or trusted educational portals. This PDF includes:

• Complete chapter text
• Diagrams and illustrations
• Solved examples and exercises

Using the PDF helps students revise effectively and practice questions for exams. Always ensure to download the latest version aligned with the CBSE syllabus.

Solved Example: Calculating Energy Yield from Respiration

Example: Calculate the total ATP produced from one molecule of glucose during aerobic respiration.

Solution:

• Glycolysis produces 2 ATP
• Krebs cycle produces 2 ATP
• Electron transport chain produces 32-34 ATP

Total ATP = 2 + 2 + 32 (approx.) = 36 ATP

This calculation helps students understand the efficiency of respiration and its role in energy supply.