Life Processes: Respiration MCQs Quiz | Class 10

Life Processes: Respiration – Detailed Explanation

Overview of Respiration

Respiration is a fundamental biological process that occurs in all living organisms. It involves the exchange of gases and the release of energy from food substances, primarily glucose. This energy is captured in the form of ATP (Adenosine Triphosphate), which serves as the main energy currency for various cellular activities, including growth, movement, and maintaining body temperature. Without respiration, cells would not have the necessary energy to sustain life.

Key Concepts of Respiration

• Definition: Respiration is the biochemical process where cells convert biochemical energy from nutrients (like glucose) into ATP, and then release waste products.
• Cellular Respiration: This term specifically refers to the metabolic reactions within cells that extract energy from organic molecules. It is a series of complex reactions that break down food molecules step-by-step.
• Energy Release: The primary objective of respiration is to break down complex organic molecules into simpler ones, releasing the stored chemical energy in a usable form for the cell.

Types of Respiration: Aerobic vs. Anaerobic

Respiration is broadly categorized into two main types based on the presence or absence of oxygen:

1. Aerobic Respiration

• Definition: This type of respiration occurs in the presence of oxygen. It is the most common and efficient form of respiration.
• Location: The process begins with glycolysis in the cytoplasm, followed by the Krebs cycle and electron transport chain in the mitochondria.
• Process: Glucose is completely broken down into carbon dioxide and water.
• Energy Yield: Aerobic respiration produces a large amount of energy, typically yielding 38 molecules of ATP per molecule of glucose.
• Equation: Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)
• Examples: Most plants and animals, including humans, perform aerobic respiration.

2. Anaerobic Respiration

• Definition: This type of respiration takes place in the absence of oxygen. It is less efficient than aerobic respiration.
• Location: Occurs entirely in the cytoplasm of the cell.
• Process: Glucose is incompletely broken down.
• Energy Yield: Produces a much smaller amount of energy, typically yielding only 2 molecules of ATP per molecule of glucose.
• Products Vary:
  • In Yeast (Fermentation): Glucose → Ethanol + Carbon dioxide + Energy
  • In Muscle Cells (during oxygen deficit): Glucose → Lactic acid + Energy
• Examples: Yeast, certain bacteria, and human muscle cells during intense, short bursts of exercise when oxygen supply cannot meet the demand.

Comparison of Aerobic and Anaerobic Respiration

Quick Revision Points

• Respiration is the process of releasing energy from food.
• ATP is the universal energy currency of cells.
• Aerobic respiration needs oxygen, yields high energy, and produces carbon dioxide and water.
• Anaerobic respiration occurs without oxygen, yields less energy, and produces lactic acid or ethanol.
• Glycolysis, the initial breakdown of glucose into pyruvate, is common to both aerobic and anaerobic respiration and occurs in the cytoplasm.
• The mitochondria are often called the “powerhouses” of the cell because they are the primary sites of aerobic respiration.

Extra Practice Questions

1. Name the two types of respiration and state the primary difference in their oxygen requirement.
2. What is the significance of ATP in cellular processes, and how is it formed during respiration?
3. Explain why muscle cells produce lactic acid during strenuous exercise.
4. Where does the initial breakdown of glucose (glycolysis) occur in a cell, and what are its products?
5. List the specific end products of anaerobic respiration in yeast and human muscle cells.