Oxygen why do we need it

As a matter of fact, we spend much of our energy obtaining the sugar and oxygen we need to produce energy. We source carbohydrates from green plants or animals that have eaten green plants, and we source oxygen from the air. Green plants release oxygen as a waste product of photosynthesis; we use that oxygen to fuel our metabolic reactions, releasing carbon dioxide as a waste product.

Plants use our waste product as the carbon source for carbohydrates. To obtain energy we must release the energy contained in the chemical bonds of molecules such as sugars. The foods we eat such as carbohydrates and proteins are digested in our gastrointestinal tract into molecules such as sugars and amino acids that are small enough to pass into the blood.

The blood transports the sugars to the cells, where the mitochondria break up their chemical bonds to release the energy they contain. Cells need oxygen to be able to carry out that process. As every cell in our body needs energy, every one of them needs oxygen. The energy released is stored in a chemical compound called adenosine triphosphate ATP , which contains three phosphate groups.

When we need energy to carry out an activity, ATP is broken down into adenosine diphosphate ADP , containing only two phosphate groups. Breaking the chemical bond between the third phosphate group and ATP releases a high amount of energy.

Our lungs supply oxygen from the outside air to the cells via the blood and cardiovascular system to enable us to obtain energy. As we breathe in, oxygen enters the lungs and diffuses into the blood. It is taken to the heart and pumped into the cells.

At the same time, the carbon dioxide waste from the breakdown of sugars in the cells of the body diffuses into the blood and then diffuses from the blood into the lungs and is expelled as we breathe out. One gas oxygen is exchanged for another carbon dioxide. This exchange of gases takes places both in the lungs external respiration and in the cells internal respiration. Fig 1 summarises gas exchange in humans. Our respiratory system comprises a conduction zone and a respiratory zone. The conduction zone brings air from the external environment to the lungs via a series of tubes through which the air travels.

These are the:. The nasal cavity has a large number of tiny capillaries that bring warm blood to the cold nose. The warmth from the blood diffuses into the cold air entering the nose and warms it. The lining of the pharynx and larynx which form the upper respiratory tract and the lining of the trachea lower respiratory tract have small cells with little hairs or cilia. These hairs trap small airborne particles, such as dust, and prevent them from reaching the lungs.

The lining of the nasal cavity, upper respiratory tract and lower respiratory tract contains goblet cells that secrete mucus.

It also traps particles, which the cilia then sweep upwards and away from the lungs so they are swallowed into the stomach for digestion, rather than getting trapped in the lungs. This mechanism of moving trapped particles in this way is known as the mucociliary escalator. The lungs are a little like balloons: they do not inflate by themselves, but only do so if air is blown into them. We can blow into the lungs and inflate them — which is one of the two techniques used for cardiopulmonary resuscitation — but that does not happen in the normal daily life of healthy people.

We have to inhale and exhale air by ourselves. How do we do that? We have two lungs right and left contained in the thoracic cavity chest. Surrounding the lungs are ribs, which not only protect them from damage but also serve as anchors for the intercostal muscles.

Beneath the lungs is a very large dome-shaped muscle, the diaphragm. All these muscles are attached to the lungs by the parietal and visceral membranes also called parietal and visceral pleura. The parietal membrane is attached to the muscles and the visceral membrane is attached to the lungs. The liquid between these two membranes, pleural fluid, sticks them together just as panes of glass become stuck together when wet.

As the visceral membrane covers, and is part of, the lungs and is stuck by pleural fluid to the parietal membrane, when the muscles in the thorax move, the lungs move with them. If air gets between the membranes, they become unstuck and, although the muscles can still contract and relax, they are no longer attached to the lung — as a result, the lung collapses.

This abnormal collection of air in the pleural space is called a pneumothorax. If the pleural fluid liquid becomes infected, the person develops pleurisy. When the intercostal muscles contract, they move up and away from the thoracic cavity. When the diaphragm contracts, it moves down towards the abdomen.

This movement of the muscles causes the lungs to expand and fill with air, like a bellows inhalation. Conversely, when the muscles relax, the thoracic cavity gets smaller, the volume of the lungs decreases, and air is expelled exhalation.

When the thoracic muscles contract, the volume of the lungs expands so there is suddenly less pressure inside them. The air already in the lungs has more space, so it is not pushing against the lung walls with the same pressure. To equalise the pressure, air rushes in until the pressure is the same inside and outside.

Conversely, when the muscles relax, the volume of the lungs decreases, the air in the lungs has less space and is now at high pressure, so the air is expelled until pressure is equalised. In short:. Because the expansions and contractions are larger in this case a bigger volume of air flows in and out of our lungs, and our body gets a larger supply of oxygen or we have more air to create sound. Observations and Results When you pulled the knot back, the space inside the bottle increased and your balloon probably filled up with air.

In the same way, when the diaphragm in our body pulls back, the chest cavity increases and air flows into our lungs, and we inhale. When you pushed the knot in, the space inside the bottle decreased, and the balloon probably deflated.

In the same way, when the diaphragm relaxes the chest cavity decreases, and air is pushed out of the lungs, and we exhale. When you pulled and pushed the knot further the balloon inflated and deflated more.

This mirrors what happens when a bigger volume of air is displaced when we breathe more deeply. This dynamic works because of air pressure, a measure of how hard air presses against objects. Air pressure increases when you decrease the amount of space the air has—and decreases when you give air more space. Close a flimsy empty plastic bottle and try to compress it. It is difficult! The air inside pushes back. Open the bottle, and try to compress the bottle again.

It is much easier. The air presses back with a much reduced force. Unless something blocks the movement, air will move from areas of high pressure to areas where the pressure is lower, and this is what happens when air rushes in or out of the lungs. When the chest cavity expands there is more space around your lungs. In this condition the lungs can expand, making it a low-pressure area, and air rushes in to balance out the difference in pressure.

Then to breathe out the chest cavity and lungs shrink. This raises the air pressure in your lungs, and the air rushes back out. This activity brought to you in partnership with Science Buddies. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options.

Go Paperless with Digital. Materials Disposable empty transparent bottle 10—16 fluid ounces made of hard plastic such as a sports drink bottle Ruler Two balloons 8-inch balloons work well Utility knife have an adult help and use caution when using the knife Adult helper Scissors Drinking straw optional Modeling clay optional Tape optional Additional balloon optional Preparation Ask an adult to cut the plastic bottle.

Place the cut bottle down on the wide opening. Lower a balloon into the bottle until only part of the balloon's neck sticks out. Fold the neck of the balloon over the top of the bottle.

The balloon represents a lung. Turn the bottle over keeping the balloon inside so the bottle top rests on the table. In the next steps you will create and add the diaphragm to your model. Make a knot in the neck of the second balloon. At the opposite side of this balloon cut off about a third of the balloon so you are left with a wide opening. Stretch the wide opening of the cut balloon over the wide opening of the bottle.

Pull the edges of the balloon far enough up the bottle so the balloon surface is gently stretched. Make sure that the knot is on the outside and located near the middle of the bottle opening. 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. 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. 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. 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. 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. 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:. To help students understand the concept of respiration, review the following information with the students, which can be found on the student esheet. 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.