Gas Exchange
Overview
Every cell in your body needs a steady supply of oxygen for aerobic respiration and must get rid of carbon dioxide waste. Plants face a similar challenge: their cells need CO₂ for photosynthesis and release O₂ as a by-product. Gas exchange is the process that moves these gases between an organism and its environment, and it depends entirely on diffusion.
In this lesson you will explore how the human lungs and the plant leaf are structured for efficient gas exchange, how the breathing mechanism ventilates the lungs, and why smoking damages the system. Edexcel tests gas exchange with diagram-labelling, data-response, and extended-writing questions across both papers.
Objectives
- Understand the role of diffusion in gas exchange
- Understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis
- Understand how the structure of the leaf is adapted for gas exchange
- Describe the role of stomata in gas exchange
- Understand how respiration continues during the day and night, but that the net exchange of carbon dioxide and oxygen depends on the intensity of light
- Investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator
- Describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes
- Understand the role of the intercostal muscles and the diaphragm in ventilation
- Explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries
- Understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease
- Investigate breathing in humans, including the release of carbon dioxide and the effect of exercise
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Gas Exchange. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which structure is the site of gas exchange in the lungs? A) Bronchus B) Trachea C) Alveolus D) Bronchiole Answer: C
- During inhalation, what happens to the diaphragm? A) It relaxes and domes upward B) It contracts and flattens C) It stays still D) It moves to the left Answer: B
- Which component of cigarette smoke reduces the oxygen-carrying capacity of the blood? A) Tar B) Nicotine C) Carbon monoxide D) Particulates Answer: C
- At night, a plant's net gas exchange at the stomata is: A) CO2 taken in, O2 released B) O2 taken in, CO2 released C) No exchange occurs D) O2 and CO2 both released Answer: B
- Which of these is NOT an adaptation of alveoli for gas exchange? A) Thick walls for protection B) Large surface area C) Rich blood supply D) Moist lining Answer: A
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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