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Explore how the body uses digested food to release energy through the process of respiration. Learn about aerobic and anaerobic respiration, the role of glucose and oxygen, and the importance of the circulatory and breathing systems.
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How is digested food used by the body? The body needs a constant supply of energy which comes from digested food. Glucose, from digested carbohydrates, is an important substance that contains stored chemical energy. When glucose reacts with oxygen,a lot of energy is released. In the body’s cells, glucose and oxygen react to release energy. Some of this is released as heat and the rest is used by the cells. What is the release of energy from glucose called?
+ ( energy) What is respiration? Respirationis the process that the body uses to release energy from digested food (glucose): carbon dioxide + + glucose oxygen water from the digestive system from the respiratory system waste product (exhaled) waste product (exhaled) This type of respiration is called aerobicrespiration because energy is released in the presence of oxygen. How do the glucose and oxygen needed for aerobic respiration get to the all the body’s cells?
Respiration and combustion Burning is the reaction between a fuel and oxygen. This reaction is called combustion: + + fuel oxygen carbon dioxide water During combustion, heat and light energy are released and carbon dioxide and water are also produced, so combustion is similar to respiration. The difference between combustion and respiration is that combustion is not a controlled reaction. Respiration is a controlled reaction that slowly releases energy from food in the body’s cells and the cells do not catch fire!
Circulation The dissolved food and oxygen needed for respiration are carried around the body by the circulatory system. The circulatory system includes the blood, blood vessels, the heart and the lungs. Which part of the circulatory system actually carries dissolved food and oxygen to the body’s cells?
Your beating heart The heart is made of very special muscle called cardiac muscle. This is because it has to keep beating for the whole of a person’s life! If you tried to do the same action repeatedly (like the heart does), your muscles would get tired and, after a while, stop working. For example, if you keep clenching and unclenching your hand, it will get tired and may even start to get cramp. Why is it important for respiration that the heart keeps beating?
Measuring pulse The heart pumps blood around the body in the blood vessels. Each time it pumps it causes the blood vessels to throb. This is called a pulse. To take your pulse: • Hold out one hand with the palm facingup. 2. Put the index and middle fingers of your other hand together. 3. Press these fingers lightly on the underside of the other wrist, just under the thumb bone.
Different types of activity What happens to the pulse while someone is running? During exercise, the pulse rises. This causes blood to be pumped around the body more quickly, which increases the amount of oxygen and glucose that can reach muscle cells. What happens to the pulse while someone is sleeping? During sleep, the pulse falls. This causes blood to be pumped around the body more slowly. This means that oxygen and glucose take longer to reach muscle cells.
What is breathing? The breathing system is used by the body to get the oxygen needed for respiration. It is also used to get rid of one of the waste products of respiration: the gas, carbon dioxide. Breathing in and breathing out are separate processes in the body. Breathing in is called inhalation. When you inhale, you breathe air, including oxygen, into your lungs. Breathing out is called exhalation. When you exhale you breathe out the contents of your lungs and get rid of the waste gas carbon dioxide.
Comparing inhaled and exhaled air What are the differences between inhaled and exhaled air? Exhaled Air Inhaled Air Oxygen: 21% Oxygen: 16% Carbon dioxide:0.04% Carbon dioxide: 4% Water vapour: small amount Water vapour: large amount What are the main differences? How could you test for the differences between inhaled and exhaled air?
carbon dioxide + + glucose oxygen water + ( energy) + glucose lactic acid energy Aerobic and anaerobic respiration When the body is able to supply its cells with the oxygen and glucose that they need, it carries out aerobic respiration. When the body cannot supply the cells with the oxygen needed to break down glucose, then it has to carry out anaerobic respiration. Energy is released without oxygen:
Not enough oxygen! + glucose lactic acid energy When anaerobic respiration takes place, lactic acidis also produced. Lactic acid builds up in the muscle cells and prevents the muscles doing their job. This is thought to cause fatigue and sometimes cramp. After exercise the body needs to remove the lactic acid before it causes damage to cells.
+ + lactic acid oxygen carbon dioxide water Oxygen debt Lactic acid is broken down by oxygen. After activity that has lead to anaerobic respiration, the person involved breathes heavily and their heart rate remains high to supply the body with the oxygen it needs. The amount of oxygen needed to remove all the lactic acid after exercise is called an oxygen debt.
