Class VII - RESPIRATION

Chapter 11

Respiration

Why do we need food?

We need food to get energy, growth and to live.

How does the energy get released from our food?

First the food gets digested and nutrients are absorbed by the body. Then, the body releases energy from the food by the process of respiration.

Respiration: It is the process of taking in oxygen and using it for release of energy by the oxidation( addition of oxygen) of food and eliminating the waste products - carbon dioxide and water.

The two main processes of respiration are:

*External respiration or breathing: Taking in air rich in oxygen(inhale) and giving out air rich in carbon dioxide(exhale).

*Internal respiration or cellular respiration: Breakdown of food by using oxygen to release energy. It occurs inside the cells.

How the energy is released from the food?

1. Ingestion: Intake of food from the mouth.

2. Digestion: Breakdown of nutrients into simpler form(Carbohydrates into glucose) by using digestive juices.

3. Absorption: The digested nutrients are absorbed by the villis present in the small intestine.

4. Breathing: Intake of oxygen and exhale carbon dioxide.

5. Transportation: The absorbed nutrients are transported to each cell through the blood.Oxygen reaches to each cell by the hemoglobin(oxygen carrier) present in the blood.

6. Respiration: Glucose is burnt in the presence of oxygen in each cell releases energy and waste products like water and carbon dioxide.

C6H12O6 + 6O2 ----> 6CO2 + 6H2O + Energy

Glucose Oxygen Carbon dioxide Water

Respiration in plants:

Plants also respire virtually all the time in order to supply their energy needs.

They respire by taking in oxygen and giving out carbon dioxide.

How to the plants respire?

The plants do not have any breathing organ. So the exchange of the gases takes place through the tiny pores which are present on the surface of the leaves called stomata.

The opening and closing of the stomata is controlled by the guard cells which are present around them.

The rate of exchange of gases in plants is much slower then in animal.

*Why we should not over water the potted plants and prevent the water logging during irrigation of crops?

Root cells also need oxygen to generate energy. They get oxygen from the air which is trapped between the soil particles. if we over water the plant, then Water replaces the air in the soil and roots are not able to breathe properly and this may affect the growth of the plants.

Why it is no advisable to sleep under the trees at night?

In plants both photosynthesis and respiration occur during the day. Since photosynthesis is the major activity during the day so more oxygen is released during the photosynthesis then it is absorbed during respiration. But photosynthesis does not occur at night only respiration takes place this means that plants only take in oxygen and release carbon dioxide at night.

Respiration in animals

Different animals respires in different ways:

1. Through cell membrane or skin:

Amoeba and Paramecium: They are unicellular organisms. the exchange of gases takes place in their body by the diffusion(Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.) through cell membrane.

Hydra and earthworm: Exchange of gases takes place by diffusion through the most outer surface(skin).

2. Through air holes:

Cockroaches grasshoppers : They have small holes called spiracles on their bodies. Air enters through these spiracles and reaches to all the body parts through the respiratory pipes called trachea and their further branches called tracheoles.

3. Through gills: Fishes use gills for exchange of gases. Gills are feathery organs full of blood vessels. A fish breathes by taking water into its mouth and forcing it out through the gills passages. As water passes over the thin walls of the gills, dissolved oxygen moves into the blood and travels to the fish's cells.

4. Through lungs: A tadpole has Gill but as it grows into frog, it develops the airbags called lungs for the exchange of gases. Frog is an amphibian it can live in both water and on the land. So the frog have lungs through which they can breathe when they are on the land and when they are in water they can breathe through their moist skin just like earthworm. Birds and mammals also have the well developed lungs where the exchange of gases takes place.

Types of respiration

Aerobic respiration: The respiration which takes place in the presence of oxygen is known as aerobic respiration. Aerobic respiration is carried out in almost all the plants and animals.

For example: When food in the form of a glucose is oxidised to release energy and produce carbon dioxide and water.

C6H12O6 + 6O2 -----> 6CO2 + 6H2O + energy

Anaerobic respiration:

*The respiration which takes place in the absence of oxygen is known as anaerobic respiration.

*Anaerobic respiration takes place in Yeast(unicellular organism) and some bacteria which can live without oxygen.

*In anaerobic respiration the glucose is broken down into alcohol and carbon dioxide without using oxygen to give energy. That's why yeast is used to make beers and wine.

C6​H12​O6​ -----------------------→ C2​H5​OH + CO2​ + Energy

Glucose absence of oxygen Alcohol carbon dioxide

The amount of energy given out in anaerobic respiration is much less than in the aerobic respiration.

*Anaerobic respiration also occurs in the muscle cells: When you do heavy exercise like long running your body cannot get enough oxygen to produce required energy, so to get additional energy anaerobic respiration occur within your muscle cell. During anaerobic respiration there is a partial breakdown of glucose to produce lactic acid. Accumulation of lactic acid in the body causes the muscle cramps.

You can get relief from these cramps by massaging the affected area or by having a hot bath both these activities improve the blood circulation in the body leading to the increase supply of Oxygen and this results in the complete breakdown of lactic acid to the carbon dioxide and water and give you the relief from cramps.

The Respiratory System in Humans

The main organs of the human respiratory system are:

*Nostrils (the passage in the nose)

* Trachea (windpipe)

* Bronchi

* Lungs.

Breathing in

* The taking in of air rich in oxygen into our body is called inhalation.

* Our lungs require the air which is moist, warm and clean.

* As the air passes through our nostrils it is moistened by the slimy mucus( secreted by the inner lining of the nose).

* The air becomes warm by the blood circulating in the nose.

* The mucus and hair present inside the nose trap the dirt dust particle and the disease causing germs.

If we breathe through our mouth we do not get clean air and this may also cause catching an infection.

To the lung

Then the air from our nose passes through the pharynx or throat gravity to the windpipe called trachea. The windpipe branches into the smaller tubes called Bronchi( singular called bronchus) which enters into a lung.

In the lungs

*Each bronchus for the divide into smaller tubes called bronchioles.

*At the end of these there are tiny air sacs called Alveoli. Each lung contain about 300 million Alveoli .

*Then the air from the bronchi reaches to the bronchioles and after that it reaches to the tiny air sacs Called Alveoli.

*The alveoli are surrounded by the blood vessels, the oxygen present in the air goes into the blood contained in the blood vessel and the carbon dioxide present in the blood passes out of the blood into the air sacs and the exchange of gases takes place in the lungs.

Circulation:

The blood take the oxygen to all the cells of the body where it is used to get the energy from the food and the carbon dioxide which is released by the cells as the waste product goes into the blood, through the blood it reaches to the lungs and then from the blood it goes into Air sacs and then into the bronchioles then into the air pipe through that it reaches to the nostrils and it is it is exhaled out by our nose.

The giving out of air rich in carbon dioxide is called exhalation.

How air enters the lungs

When we breathe in air, the diaphragm goes down by increasing the space in the chest cavity and allow the air to enter the lungs and lungs expand.

When we breathe out, the diaphragm moves up by decreasing the space in the chest cavity and pushes the air out of lungs.

Link of part 2 - https://youtu.be/STHLclSKDZo

Link of part 3- https://youtu.be/g_bKOhW5l88

Exercise

Oral Questions

Page 120

Q1. Respiration and breathing are the same. Do you agree? Give reasons.

Ans. No respiration and breathing are the different processes.

Respiration:

*It is the process of taking in oxygen and using it to release the energy from food.

*It is the chemical process due to the formation of new substances.

Breathing:

*It is the process which involves inhalation (taking in air rich in oxygen) and exhalation (giving out a rich in carbon dioxide).

* It is a physical process because no new substance is formed.

Q2. Exchange of gases for respiration occurs in both plants and animals. In which of these is the rate of exchange of gases faster?

Ans: The rate of exchange of gases for respiration occurs faster in animals as compared to plants because the animals require more oxygen to produce energy from food in order to perform their daily metabolic(the sum total of the chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste material, etc.) and physical activities.

On other hand plants require energy to perform only the metabolic activities.

Q3.Exchange of gases in the animal takes place in many ways. Name three.

Ans

1. Through cell membrane or skin:

In amoeba and Paramecium (unicellular organisms) - cell membrane.

In hydra and earthworm - moist outer surface (skin).

2. Through Gills: Fishes and tadpoles - Gills

3. Through air holes: Cockroaches and grasshopper - small opening called spiracles.

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Oral questions

Q1. In humans the exchange of gases occur in lungs. In which part of the lungs does it takes place?

Ans. Alveoli (tiny air sacs present at the end of the bronchioles).

Q2.Oxygen is carried to the cells by the blood. In what form is Oxygen carried in the blood

Ans. Blood has a substance called haemoglobin which bind itself with oxygen to form the oxyhaemoglobin

Q3. What process occurs during cell respiration?

Ans. During cellular respiration oxidation( addition of oxygen) of glucose takes place in order to produce the energy and waste products like carbon dioxide and water inside the cell.

Q4.Cellular respiration can occur even without oxygen. What is such respiration called

Ans. Anaerobic respiration.

Q5. Which of these- combustion or cellular respiration is a faster process?

Ans. Combustion is a faster process because combustion occurs at high temperature and cellular respiration occurs only at body temperature.

Page 126

A. Choose the most appropriate answer

Q1.In insects, exchange of gases takes place through

a. spiracles b. gills c. lungs d. stomata

Q2. Through which tubes does air enter the lungs from windpipe?

a. bronchi b. bronchioles c. alveoli d. trachea

Q3. Where in the respiratory system does oxygen from the air breathed in pass into the blood?

a. trachea b. bronchi c. bronchioles d. alveoli

Q4. Which of these is not true about cellular respiration?

a. It releases energy

b. It occurs only during the day

c. It utilizes Oxygen and liberate Carbon dioxide

d. It occurs in all living things

Q5. Which of these is true about anaerobic respiration?

a. Oxygen is utilised

b. Carbon dioxide is given out

c. Amount of energy released is more than in aerobic respiration

d. Sometime it occurs in the human body also

Q6. Exchange of gases in plants takes place through the

a. stomata b. roots c. buds d. entire leaf surface

Q7. During which process is energy released?

a. External respiration

b. Internal respiration

c. Inhalation

d. Exhalation

Q8. Which of these is not true?

a. combustion is a faster process than respiration

b. combustion occurs at high temperature than respiration

c. In combustion energy is released in several steps whereas in respiration it is released in a single step

d. combustion can occur anywhere but respiration only occurs in living cells.

B. Very Short- Answer Questions. Give the answer in one word

Q1.Give one word for the process of release of energy by oxidation of food

Ans. Cellular respiration

Q2.Name the flap that closes the windpipe when you swallow food.

Ans. Epiglottis is the flap that closes our windpipe when we swallow food.

Q3. Which muscular part of the body present in the chest cavity helps air to be breathed in and out?

Ans. Diaphragm is the muscular part of the body present in the chest cavity that helps air to be breathed in and out.

Q4. Taking in oxygen and giving out carbon dioxide is called ___________or ____________ respiration.

Ans. Taking in oxygen and giving out carbon dioxide is called breathing or external respiration.

Q5. Name the pores in the stems and leaves of plants through which exchange of gases takes place.

Ans. Stomata are the pores in the stems and leaves of plants through which exchange of gases takes place.

Q6. In Amoeba, exchange of gases occurs by ________ through the cell membrane.

Ans. In Amoeba, exchange of gases occurs by diffusion through the cell membrane.

Q7. Exchange of gases on fishes occurs through gills. True of false?

Ans. True. Q8. During cellular respiration, the sugar molecules in food are _________ to form carbon dioxide and water.

Ans. During cellular respiration, the sugar molecules in food are oxidised to form carbon dioxide and water.

Q9. Respiration without oxygen is called aerobic respiration. True of false?

Ans. False. Q10. Trace the path of oxygen in humans during respiration by filling in the blanks with the main organs of the respiratory system: Nostrils and nasal cavity →________ → __________ → lungs → __________ → __________ → cells

Ans. Path of oxygen in humans during respiration: Nostrils and nasal cavity →→ pharynx →→ trachea and bronchi →→ lungs →→ bronchioles and alveoli →→ blood →→ cells.

Q11. The substance present in blood which transports oxygen is _________

Ans. The substance present in blood which transports oxygen is haemoglobin.

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C. Short answer questions: Answer in a sentence or two

Q1.What is 'oxidation'?

Ans. Oxidation means addition of oxygen. During the cellular respiration oxidation of glucose takes place in presence of oxygen to release energy and waste products like carbon dioxide and water.

C6H12O6 + 6O2 -----> 6CO2 + 6H2O + energy

Q2. Why should we not over water potted plants?

Ans. We should not over water potted plants because the water replaces the air in the soil and the roots cannot breathe and this affects the growth of the plants.

Q3.What do you mean by stomatal apparatus?

Ans. Stomata along with its nearby guard cells and other cells are called the stomatal Apparatus.

Q4.What are the main organs of the respiratory system?

Ans. The main organs of the human respiratory system are:

*Nostrils (the passage in the nose)

* Trachea (windpipe)

* Bronchi

* Lungs.

Q5. What happens during cellular respiration?

Ans. During cellular respiration, the sugar molecules in the food are oxidized to form carbon dioxide and water and releases energy.

C6H12O6 + 6O2 -----> 6CO2 + 6H2O + energy

Q6. Why does breathing become faster while doing exercise?

Ans. Our body needs more energy while exercising. In order to produce more energy in the body. Our body requires more oxygen for the fast burning of the food. Oxygen reaches in our body by the breathing process.

Q7. What chemical reaction occurs during anaerobic respiration in yeast?

Ans. During anaerobic respiration, Glucose is broken into alcohol, carbon dioxide without using oxygen to give energy

C6​H12​O6​ -----------------------→ C2​H5​OH + CO2​ + Energy

Glucose absence of oxygen Alcohol carbon dioxide.

Q8. An athlete suffers from cramps while running a race. How can you help him overcome the cramps?

Ans. Cramps can be relieved by massaging the affected part or by having a hot bath. Both these activities improve the circulation of blood in the body leading to the increased supply of oxygen.

D. Long-Answer Questions: Answer these questions.

1. Name and explain in one sentence each, the two main processes of respiration.

Ans. The two main processes of respiration are:

External respiration: Taking in air rich in oxygen and giving out are rich in carbon dioxide.

Cellular respiration: Release of energy by the oxidation of food in presence of oxygen inside the cell.

2. How does exchange of gases occur in the following: a. fish b. Cockroach

Ans.

a. fish: Fishes use gills for exchange of gases. Gills are feathery organs full of blood vessels. A fish breathes by taking water into its mouth and forcing it out through the gills passages. As water passes over the thin walls of the gills, dissolved oxygen moves into the blood and gives out carbon dioxide through its wall.

b. Cockroach: They have small holes called spiracles on their bodies. Air enters through these spiracles and reaches to all the body parts through the respiratory pipes called trachea and their further branches called tracheoles.

3.How do the nostrils contribute to the process of breathing?

Ans.

1.Taking in of air rich in oxygen happens through the nostrils.

2.The inner lining of the nostril secrete the mucus which make the air moistened.

3.The blood circulating in the nostrils make the air warm.

4. The mucus and the hair present in the nostrils traps dust particle and germs in the air & make the air clean.

4. Draw a labelled diagram of the Apparatus you will use to show that heat is produced during the respiration in seeds. Why are the two flasks used in the experiment?

Ans. Two flasks are used in the experiment (one containing the germinating seeds and other containing the boiled seeds) to show that heat is produced during respiration. Respiration occurs in germinating seeds, but not in boiled seeds. The thermometer inserted in the flask containing germinating seeds shows higher temperature than the one inserted in the flask containing boiled seeds. This shows heat is produced during respiration.

5. What happens to the air breathed in, once it reaches the lungs?

Ans. In the lungs each bronchus branches out into the smaller tube called bronchioles and at the end of these tubes there are tiny air sacs called Alveoli. The air we breathe in reaches these air sacs and these sacs are surrounded by the blood vessel. The oxygen present in the air goes into the blood contained in the blood vessel and the carbon dioxide present in the blood passes out to the blood into the sacs and hence the exchange of gases takes place in lungs.

6. Explain with the help of a diagram, the structure of the human lungs, and how exchange of gases occur in the lungs.

Ans. The main organs of the human respiratory system are:

*Nostrils (the passage in the nose)

* Trachea (windpipe)

* Bronchi

* Lungs.

Breathing in

* The taking in of air rich in oxygen into our body is called inhalation.

To the lung

Then the air from our nose passes through the pharynx to the windpipe called trachea. The windpipe branches into the smaller tubes called Bronchi( singular called bronchus) which enters into a lung.

In the lungs

*Each bronchus for the divide into smaller tubes called bronchioles.

*At the end of these there are tiny air sacs called Alveoli. Each lung contain about 300 million Alveoli .

*Then the air from the bronchi reaches to the bronchioles and after that it reaches to the tiny air sacs Called Alveoli.

*The alveoli are surrounded by the blood vessels, the oxygen present in the air goes into the blood contained in the blood vessel and the carbon dioxide present in the blood passes out of the blood into the air sacs and the exchange of gases takes place in the lungs.

The giving out of air rich in carbon dioxide is called exhalation.

7. How are combustion and cellular respiration similar to each other in what ways are they different?

Ans. Similarities: Both combustion and cellular respiration takes place in the presence of oxygen.

In both of them heat and energy are released.

Differences between them:

Combustion Respiration

It is a fast process. It is a slow process.

It takes place only at high temperature. It takes place at body temperature.

It can happen anywhere. It can take place only in living cells.

It is a single-step process It is a multi-step process,

Energy is released in the form of heat and light. Energy is stored in the form of ATP.

8. How will you show that exhaled air has more carbon dioxide than inhaled air?

Ans. Carbon dioxide turns lime water milky. Based on this principle, experiment can be designed to show that exhaled air has more carbon dioxide than inhaled air.

Take two test tube each of them half filled with lime water.

Using two holed stoppers, glass tube and clips, set up the apparatus as shown in the following diagram.

Use the rubber tube at the middle to breathe in and out to the mouth.

As you exhale air through the rubber tube and when the exhaled air passes through the lime water in the test tube B, the lime water turns milky due to the presence of carbon dioxide in the air.

9. What is the difference between breathing and cellular respiration?

Ans. Differences between breathing and cellular respiration:

Breathing Cellular Respiration

*It is a physical process in which * It is oxidation of food

exchange of gases takes place.

*It does not involve any chemical reaction. * It involves chemical reaction.

*It occurs outside the cells * It occurs inside the cells.

*No energy is liberated in the process. * Energy is liberated during the process.

10. What is anaerobic respiration does it occur in the human body also?

Ans. Anaerobic respiration: Respiration process which takes place in the absence of oxygen

During heavy exercise and long distance running, our body cannot get enough oxygen to produce the required energy In order to get the additional energy anaerobic respiration occurs within muscle cells this includes the partial breakdown of glucose to produce energy.

11. Why do we sometimes suffer from muscle cramps while exercising?

Ans. Cramps occur while exercising because of accumulation of lactic acid in the muscle cells. During exercise, body needs more energy, but it cannot get more oxygen for oxidation of food and for providing energy. The additional energy in muscle cells is provided by anaerobic respiration in which partial breakdown of glucose into lactic acid takes place. This lactic acid accumulates in muscle cells and causes cramps.

Hots Questions: Think and answer.

1. Is it wise to sleep under a tree a.during a day b. at night? Give reason

Ans.

a. During a day: Yes, it is advised to sleep under the tree during the day because in plant during the day in the presence of sunlight photosynthesis and respiration both the processes takes place. Photosynthesis is the major activity, during that process plants releases the oxygen.

b. At night: No, it is not advised to sleep during night under the tree because at night only respiration process takes place in plants in which plants take in oxygen and release carbon dioxide at night. Therefore, if one sleeps under a tree during night, he/she will get oxygen-deficient air.

2. A person put warm water in an aquarium, thinking that the fish would be more comfortable in it. However, the fish died. What can be the reason for this? (HINT: the solubility of a gas in water goes down as its temperature increases)

Ans. A fish needs the dissolved oxygen in water for respiration. Upon an increase in temperature, the solubility of oxygen in water decreases. The fish cannot get enough oxygen for respiration and hence dies.

3. When you run, your breathing becomes faster as you need more oxygen. But why does your rate of heartbeat also increase?

Ans. Body needs more oxygen during running and oxygen which is carried by blood to all the parts of the body. Heart needs to pump more blood, carrying oxygen, to all the body parts during running. In order to supply more blood, the heart rate also increases during running.