To understand that human beings (as well as other animals) perform the respiration process because we need air to breathe and because oxygen is ultimately the fuel that allows our cells to produce energy from the food we eat.
The main focus of this lesson is to review the basics of respiration (breathing) and to teach students the importance of oxygen to the human body. To burn food for the release of energy stored in it, oxygen must be supplied to cells, and carbon dioxide removed. Lungs take in oxygen for the combustion of food and they eliminate the carbon dioxide produced. It is also important to point out to the students that a lack of oxygen or breathing pure oxygen is detrimental to our health. Another focal point of this lesson is that respiration is fundamental for our health and overall fitness. In fact, our bodies can use oxygen more efficiently if we exercise and eat properly.
By the end of elementary school, students should know that by breathing, people take in the oxygen they need to live. This basic knowledge allows middle-school students to develop a more sophisticated understanding of how respiration works in terms of basic macroscopic (e.g., major organs involved) and microscopic (e.g., cellular) processes involved with breathing.
By the end of middle school, students should know that to burn food for the release of energy stored in it, oxygen must be supplied to cells and carbon dioxide removed. They should understand the following macroscopic and microscopic processes: lungs take in oxygen for the combustion of food and they eliminate the carbon dioxide produced; the urinary system disposes of dissolved waste molecules; the intestinal tract removes solid wastes; the skin and lungs rid the body of heat energy; and the circulatory system moves all these substances to or from cells where they are needed or produced, responding to changing demands.
When students take biology in high school, they will receive instruction in the process of cellular respiration (glycolysis, Krebs cycle, electron transport chain, etc.) that will fill in the details of exactly how glucose from food is broken down to yield energy, or ATP, so it is not necessary that students have this detailed understanding at the middle-school level. It would be best if this lesson could come after a discussion of the circulatory system.
Research shows that students up to the age of seven have little knowledge about the human organism; however, by age nine or ten, students have a marked increase in their knowledge. Specifically in terms of the respiratory system, lower elementary-school students may not know what happens to air after it is inhaled but upper elementary-school students associate the lungs' activities with breathing and may understand something about the exchange of gases in the lungs and that the air goes to all parts of the body. (Benchmarks for Science Literacy, p. 345.)
This lesson may need to be taught over two or three class periods. There is a brief experiment performed in the Development where students should light a candle. You could choose to do this as a demonstration instead, in which case you would just need one candle, a match, and a glass or jar.
Ask one student to come to the front of the class to blow up a balloon. He/she should hold it and then allow it to deflate. Then ask: “What organ in your body is similar to a balloon?” (The lungs.)
Refer students to the Oxygen Machine student esheet, which will guide them to The Mystery of Mallory & Irvine '24 on the PBS website. After students have read the story, discuss the questions posed on the esheet (students can record their answers on The Oxygen Machine student sheet). Use these questions to get students started in thinking about oxygen and the body. Do not worry so much at this point about right or wrong answers.
- What seems to be the biggest obstacle climbers faced in climbing Mount Everest?
(The lack of enough oxygen seems to be the biggest obstacle.)
- What is the “English Air” referred to in the story? Why did the climbers use it?
(The English Air is oxygen stored in bottles. Climbers use it to assist breathing.)
- Why does the human body need oxygen?
(The human body needs oxygen so it can combust food to release the energy stored in it.)
Next, project the introductory page from Exposure on the PBS website and read the three questions on this site slowly to the students to stimulate their thinking about respiration. If you are not able to project the page to the whole class, copy the questions on the board. They are:
- What happens to your body when it's exposed to extreme altitudes?
- How does the lack of oxygen affect the brain?
- If there were a mountain higher than Everest, would humans be capable of reaching the summit?
Tell students to keep these questions in mind as they go through this lesson.
Now ask students to answer these three questions on respiration.
- What gas in the air is important for human survival?
(It is oxygen.)
- What gas (which is a waste product) is exhaled from the body when breathing?
(Carbon dioxide is exhaled from the body.)
- What organ works in concert with the lungs?
(The heart works in concert with the lungs.)
To help students understand the concept of respiration, review the following information with the students, which can be found on the student esheet.
“Respiration (breathing) is so automatic that we rarely think about it, unless we feel that enough air is not getting into our bodies. The drawing on the Mechanics of Respiration student sheet illustrates the basic parts of the body involved with respiration. Respiration is the process that allows us to breathe in oxygen and exhale carbon dioxide. Oxygen is then used in our cells as the fuel that transforms the food we eat into energy.”
Students will go through a series of resources to learn about: the respiration process (basic mechanics), its importance as fuel to our cells, and its importance in health and disease.
Basic Mechanics of Respiration
Using the esheet, students should go to and read the Mechanics of Respiration to learn about the process of respiration. This resource will introduce them to the structures and functions of the respiratory system.
When students have finished, review the information on the page by discussing these questions:
- Which gases are exchanged in the process of respiration?
(Oxygen and carbon dioxide are exchanged.)
- Why might it be better to breathe in through the nose than through the mouth?
(The nasal cavity has structures that clean and filter the air before it reaches your lungs.)
- What are the four parts of your respiratory system and what do they do?
(The nose and mouth make up the first part where air enters your body. The trachea, or windpipe, is the second part and it delivers air to the lungs. Your lungs are the third part where oxygen is absorbed by the blood, which brings it to the rest of the body. Finally, the diaphragm is the fourth part. It makes up the floor of your rib cage.)
- What happens to air once it reaches your lungs?
(It flows into large tubes called bronchi and from there into smaller, branching tubes called bronchioles. The bronchioles move the air into tiny air sacs called alveoli, where the oxygen is separated from the rest of the air and moved to tiny blood vessels called capillaries.)
- What part of the blood carries oxygen to the rest of your body?
(Hemoglobin carries oxygen to the rest of your body.)
Respiration as Combustion for the Production of Energy
Using the esheet to guide them, students should read How the Body Uses O2 on the PBS website. They should focus on #7 and #8 because they review how oxygen is involved in energy production; the other information reviews the respiration process. This site discusses atmospheric pressure, which is usually not covered in depth until high-school chemistry so you may need to define this for students if they are not familiar with it.
Students should answer these questions:
- Why do we breathe?
(We breathe because oxygen is needed to burn the fuel [sugars and fatty acids] in our cells to produce energy.)
- What happens in the process of respiration?
(Oxygen is brought into the lungs via breathing, where it is transported by red blood cells to the entire body to be used to produce energy. Once the red blood cells return to the lungs, the "burnt" carbon dioxide is exhaled).
- What cellular component allows the combustion process to occur?
(The energy station of the cells, called mitochondria, process oxygen to power the cells. As part of the combustion process, carbon dioxide is released.)
Next, discuss the combustion process in terms of producing energy via respiration. You can use the information on The Oxygen Machine teacher sheet to help you with this discussion. Follow up the discussion with a simple experiment/demonstration:
Light a candle and ask students to observe the behavior of the fire for five minutes. Then put a glass or a jar on top so that the fire will eventually go out. Ask students what will happen when the glass is put on top of the fire. Also ask students what happens to the glass or anything else that comes near the flame (it gets hot because of the release of heat energy).
Now ask students to think of food again as the source of energy. Help them to establish a relationship. Begin by pointing out that fire is only one form of oxidation! Oxidation also occurs in your body: When the carbohydrates and fats in your body combine with the oxygen you inhale, they produce carbon dioxide (CO2) and release energy, oxidization.
To summarize this part of the lesson, allow students to work in small groups to answer this question: “What is the relationship between breathing and eating?” Students should explain using their own words, an example, or simply by drawing a diagram or a picture to explain the concept. (Students should discuss the relationship in terms of oxidation.)
The Importance of Respiration: Health, Fitness and Disease.
Using the esheet to guide them, students should read Hear the Experts on the PBS website and OA Guide to High Altitude: Acclimatization and Illnesses on the Princeton University website.
After students have read the information on the websites, review the information with them. You can use the text in the second part of teacher sheet to help.
To summarize and review this part of the lesson, students should answer these questions:
- What factors affect how much oxygen your body needs?
(Age, sex, weight, physical fitness, and level of physical activity being performed affect how much oxygen your body needs.)
- What happens when your body doesn’t get enough oxygen?
(Fatigue, poor concentration, fainting, hyperventilation, confusion, and possibly death are all possible effects.)
- Can you think of a situation (either a physical activity or a medical problem) where you wouldn’t get enough oxygen?
(Some examples include climbing, scuba diving, and an asthma attack.)
- Would your body react differently if you ascended to the summit of Mt. Everest (29,000 feet above sea level) via a balloon ride versus taking several weeks to ascend the mountain? Why or why not?
(Yes. If you climb, you are giving your body several weeks to adjust to the continual decrease in oxygen pressure as you get further away from sea level. In the balloon example, the body doesn’t have adequate time to make the necessary changes to adapt to the decreased oxygen pressure levels, which could lead to death.)
Give students approximately 10 minutes to write a two-paragraph summary of what they learned from this lesson. Ask for some volunteers to read what they learned.
For your use, here is a summary example:
“We depend on air for our survival. More specifically, we depend on oxygen to breathe. Without it, we would die. However, with it, we thrive. Enough oxygen must reach the tiny cells throughout our body to feed them, giving them the energy necessary for life.
A fit body can absorb more oxygen. A body that is not overweight also needs less oxygen. Fitness combined with a healthy and balanced diet is the true secret of having a healthy life!”
You can use the Making Bottled Lungs activity to extend this lesson.
Why Do We Breathe on the Canadian Lung Association website offers a basic review of respiration.
Research has shown that hyperoxia (too much oxygen) and hypoxia (too little oxygen) can damage our cells, leading to overproduction of reactive oxygen species (ROS) or free radicals (chemical derivatives of oxygen that have a free electron and because of this are very unstable and highly reactive). These websites review information about free radicals, antioxidants, and exercise:
In terms of “too much oxygen,” a great activity for students would be to research why scuba divers don’t use tanks of pure oxygen.