Class 10 Respiration|Life processes Important questions-4

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Question 1

Why do organisms need food?


Organisms need food for obtaining energy to perform the vital functions.

Question 2

What is a respiratory substrate?


The substance used by the cell to derive energy is called a respiratory substrate

Question 3

How does food yield energy?


Food is broken energy in the form of ATP.

.Question 5

Name a few respiratory substrates. Which of them is most commonly used?


Carbohydrates, fats, proteins are some of the respiratory substrate. The most commonly used of them is glucose, a carbohydrate.

Question 6

Give the general equation for respiration?


C6H12O6+6O2-------- 6CO2+6H2O+38ATP


Question 7

What are the stages of respiration?


Respiration takes place in the following stages:

External respiration or gaseous exchange: The exchange of gases between the environment and the body is called external respiration or gaseous exchange.

Internal respiration: The bio-chemical processes involved in respiration which break down the substrate to release energy take place in the tissues within the cells of an organism. Thus, this is also called the cellular or tissue respiration.

Question 8

What is the respiratory surface?


The area where the gaseous exchange takes place is called the respiratory surface.

Question 9

What are the characteristics of an ideal respiratory surface?


The respiration surface should have the following characteristics:

It should be permeable to the gases.

It should be thin (1mm or less) to allow effective diffusion.

It should be richly supplied with blood vessels or bodily fluids to allow maximum uptake of oxygen in minimum time.

Question 10

How does gaseous exchange take place in the lower plants?


In lower plants exchange of gases takes place through the general body surface as they are not highly modified or specialized.

Question 11

Which part of a plant is involved in the gaseous exchange?


The entire plant is involved in gaseous exchange- leaves (stomata), stem (lenticels) and general surface of the roots.

Question12: How does gaseous exchange take place in the leaves?

Answer: The leaves have openings called the stomata which are generally on the lower surface of the leaves. It is through the stomata that the gases and water vapour diffuse in and out easily. The oxygen diffuses in through the stomata and then enters the leaf cells.

Similarly, the carbon dioxide produced by the leaf cells diffuses out through the stomata.

Question 13

What are lenticels?


In woody stems, the entire surface is covered by dark which is impervious to s gases or water.

However, there are certain openings or pores in the layer of bark. These are called the lenticels. They are visible more raised then the general surface of the stem. At the base of the lenticels are loosely arranged cells which allow the diffused gases to pass in and out.

Question 14

What are pneumatophores?


Plants which grow in salty water show specialized roots called the on. These are roots growing out of the surface of water with numerous pores on their surface.

Question 15

How does exchange of gases take place in fish?


Fish have specialized organs called the gills for exchange of gases.

Question 16

From where do the fish obtain their oxygen supply?


Fish utilize the oxygen dissolved in the water in which they live.

Question 17

What is operculum?


It is a plate- like cover made up of muscles and bony layer present on the outer side of the gills.

Question 18

Describe inspiration and expiration in fish?


Water moves through the gills by the coordinated action of mouth and the operculum. Taking in water and thereby oxygen is called inspiration and exit of water is called expiration.


When the mouth is open, the space inside buccal cavity increases which reduces the pressure inside. This makes the water enter the buccal cavity. At the same time, the water pressure outside presses the posterior end of the operculum against the body preventing the entry of water into the gills from this end. The opercular cavity is enlarged by the contraction of the pressure in the opercular cavity and draws water from the buccal cavity into the opercular cavity. This water flows over the gill filaments during which the exchange of gases between the capillaries and the water take place.



The mouth and the entrance to the esophagus close and the floor of the buccal cavity rises. This pushes the water out into the opercular cavity. This water which is under high pressure forces open the operculum at the posterior end and moves out into surrounding.

Question 19

Which are the respiratory organs in man?


The respiratory organs in man are the lungs.

 Question 20

Where are the lungs in man situated?

Answer: In man, there are a pair of lungs present in the thoracic cavity. They are found next to the heart. Towards the front they are protected by the chest wall that is formed by the rib cage and the muscles associated with the ribs. There are 12 pairs of ribs and two sets of muscles called the outer and inner intercostal muscles in the chest wall. Posteriorly, lungs are bound by a muscular diaphragm that separates the thoracic cavity 

Lungs are spongy, lobed and elastic organs that are broad at the bottom and tapering towards the top. They consist of air sacs, the alveolar ducts, bronchioles (which connect them to the respiratory tract) and the blood vessels.

Each lung in enclosed by two membranes called the outer and the inner pleural membrane. The membranes enclosed a space called the pleural cavity that contains a fluid. The lungs are capable of expanding and contracting as they are elastic organs. Lubrication for their free movement is provided by the fluid in the pleural cavity.

Question 22

Name the various parts of the respiratory tract.


The various parts of the respiratory tract are nose, pharynx, glottis, larynx, trachea, bronchus, bronchioles, alveolar ducts and alveoli.

Question 23

Write a brief note about the nasal cavity?


The nasal cavity opens to the outside through the opening called the nostrils. The nasal cavity is lined by fine hairs that filter the dust particles from the air. It is separated from the mouth by hard and soft palate that form its floor. It opens into the region called the pharynx.

Question 24

What are the functions of the pharynx?


pharynx is the region of the respiratory tract that connects the nasal cavity to the larynx. It is a region which is common to the passage of food and air. It has two functions:

Taking in of extra air when required. For example, during heavy exercise.

Allowing passage of air when the nose is blocked.

Question 25

What is the significance of respiration?


Respiration is an important process in nature. It is the process by which the organic compounds are broken down to release energy in the form of ATP molecules. Respiration makes use of oxygen and releases carbon dioxide, which is then used by plants during photosynthesis that releases oxygen. Thus, respiration has an important role to play in maintaining the delicate oxygen- carbon dioxide balance in nature.


Question 26

Write short notes on trachea. 


Trachea is also called the windpipe. The trachea are held open with the help of C-shaped cartilaginous rings. The open ends of the rings are towards esophagus- the food pipe. Trachea is situated in front of the esophagus. The cartilages keep the larynx and trachea from collapsing even when there is no air in them. The trachea then into two main branches called bronchi.

Question 27

How do the trachea and bronchi keep the respiratory tract healthy?


The trachea and the bronchi and lined with ciliated epithelial cells and secretory cells (goblet cells). The secretory cells secrete mucus which moistens the air as it passes through the respiratory tract and also traps any fine particles of dust or bacteria that have escaped the hairs of the nasal cavity. The cilia beat with an upward motion so that the foreign particles along with the mucus is sent to the base of the buccal cavity  from where it may be either swallowed or coughed out.


How does exchange of gases take place in the alveoli?


The capillaries lining the alveoli have impure blood which has low concentration of oxygen. So, the oxygen from the air easily diffuses into the blood through the thin barriers of the alveolus wall. Similarly when the concentration of carbon dioxide is quite high in the blood, the gas easily diffuses out into the alveolar space. From here, the air which has comparatively more concentration or carbon dioxide than the air that entered it, leaves the lungs.

Question 29

What is oxyhemoglobins and how is it formed?

Answer: Oxyhemoglobin is the compound formed by the combination of hemoglobin and oxygen. The hemoglobin pigment (Hb) has an affinity for oxygen. in the lungs, it combines with oxygen and forms HbO2, oxyhemoglobin.

Hb+ O2------- HbO2


Question 30

How does carbon dioxide get transported in the blood?


Carbon dioxide is transported in the blood as bicarbonate ions in the plasma region of the blood.

Question 31

What is inspiration?


During inspiration, the outer intercostal muscles contract which raises the chest cavity or the ribs. This is accompanied by the lowering of the diaphragm. Together these movements serve to increase the area of the thoracic cavity which reduces the pressure. The air from outside rushes into the lungs


Question 32

What is expiration?


During the expiration or exhalation, the inner intercostal muscles contract bringing the ribs back to the original position and the diaphragm is also raised back. This reduces the space in the chest cavity and increases the pressure. This expels the air out of the lungs.


Question 33

Define the terms

(a) Lung capacity

(b) Vital capacity.


Lung capacity

Vital capacity

The maximum air that can be held in the two lungs at any time is called the lung capacity. It is about 6000 ml.

The maximum volume of air that can be exchanged in one breath in and out is called the lung capacity. It is about 5000 ml.


Question 34

Define the terms:

(a) Inspiratory reserve volume

(b) Expiratory reserve volume


Inspiratory reserve volume

Expiratory reserve volume

The volume of air that can be drawn in ater normal inspiration is about 1500ml and is called the inspiratory reserve volume (complemental air).

The volume of air that can be expelled out after a normal expiration is about 1500ml and is called the expiratory reserve volume (supplemental air).



Question 35

What is breathing?


The mechanism of taking in oxygen and giving out carbon dioxide is called breathing.

Question 36

Breathing and respiration are not synonymous. Why?


Respiration involves both the mechanical and the bio- chemical processes whereas breathing is only the mechanical or physical process of exchange of gases.

Question 37

What is cellular respiration?


In the cells, the substrate, often glucose, is broken down into carbon dioxide and water in the presence of oxygen. This process releases energy and involves a series of bio- chemical reactions. This is called cellular respiration.

 Question 38: What are the major steps of cellular respiration?

Answer: The major steps of cellular respiration are:


Krebs’s cycle

Electron Transport Chain

Question 39

What is anaerobic respiration?


Respiration or breakdown of food in the complete absence of free oxygen is called anaerobic respiration.

Question 40

Name two anaerobes.


E.coli and Clostridium tetani are two anaerobes

Question 41

Where do you find anaerobic respiration in animals?


In animals, anaerobic respiration can be seen in certain skeletal muscle cells when they are short of oxygen. for example, during the period of heavy exercise.

Question 42

What are the types of anaerobic respiration?


Anaerobic respiration is of two types based on the products formed.

Alcoholic Fermentation: It occurs in plants like the yeast ( a fungs). It can be represented as follows:

Lactic acid Fermentation: It occurs in animal cells. It can be represented as follows: glucose-----2 lactic acid+ 2ATP

During this process, no carbon dioxide is released.

Question 43

Which type of respiration is more efficient- aerobic or anaerobic? Why?


Aerobic respiration is more efficient as it produces 38ATP molecules for every molecule of glucose used up. Whereas anaerobic respiration yields only 2 ATP molecules for each molecule of glucose

Question 44

What are the uses of fermentation?


Fermentation is a commercially important process. It is following processes:

Manufacture of alcohol

Curing of tea leaves, tobacco, etc

Formation of curd from milk

Manufacture of vinegar, an industrially important compound.



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