Biology For Class X - Chapter No. 1 - Gaseous Exchange - Question Answers

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CHAPTER 1: GASEOUS EXCHANGE
Question Answers

Q.1: Define gaseous exchange? Or Why gaseous exchange occur in living organisms?
Ans: All living organism must need to take in oxygen and give out carbon dioxide gases with their environment to carry out their vital functions such as respiration. In addition to respiration, photoautotrophs like plants do carry out the process of photosynthesis by taken in carbon dioxide gases and given out oxygen. This Process of exchange gases in all living organisms is termed as gaseous exchange. Aquatic organisms exchange gases with water while terrestrial one with air.

Q.2: Describe the gaseous exchange in plants?
Ans: Gaseous Exchange In Plants:
Plants exchange gases for the process of photosynthesis and respiration. The process of exchange of gases in plants takes place mainly through minute openings called stomata present in leaves. The roots and stem do exchange gases for respiration.

Photosynthesis: During the process of photosynthesis, carbon dioxide is taken in while oxygen is given out. During daytime (i.e. in the presence of sunlight), green parts (contain chlorophyll) of the plants carry out the process of Photosynthesis to prepare complex food molecules (organic molecules) by utilizing simple molecules such as carbon dioxide gas and water. During this process, carbon dioxide gas is taken in while oxygen gas is released as a by-products is given out.

Respiration: In respiration, oxygen is taken in and carbon dioxide is given out. Respiration takes place in all living cells. It is the process in which food is oxidized to release energy. In aerobic respiration, it involves taking in oxygen and giving out carbon dioxide.

Q.3: Define respiration and photosynthesis? and Differentiate between respiration and photosynthesis
Ans: DEFINITIONS:
Photosynthesis:
During daytime, green parts of the plants carry out the process of Photosynthesis to prepare complex food molecules (organic molecules) by utilizing simple molecules such as carbon dioxide gas and water in the presence of sunlight and chlorophyll. During this process, carbon dioxide gas is taken in while oxygen gas is released as a by-product is given out.

Respiration:
In respiration, oxygen is taken in and carbon dioxide is given out. Respiration takes place in all living cells. It is the process in which food is oxidized to release energy.

Glucose + Oxygen → Carbon dioxide + water + Energy
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

Difference Between Photosynthesis And Respiration:

S.NO.	Photosynthesis	Respiration
1.	Anabolic process.	Catabolic process.
2.	Synthesis of food from simple, inorganic substances.	Breaking down of food into inorganic substances.
3.	Requires light energy.	Does not require light energy.
4.	Occurs in plants.	Occurs in all living organisms.
5.	Uses carbon dioxide gas.	Uses oxygen gas.
6.	Releases oxygen gas.	Releases carbon dioxide gas.
7.	Takes place during day-time.	Takes place all the times.
8.	Chlorophyll is required.	Chlorophyll not required.

OR

S.NO.	Photosynthesis	Respiration
1.	An anabolic process in which synthesis of food (carbohydrate) occurs from simple inorganic substances.	A catabolic process in which breaking down of food (carbohydrate) occurs into inorganic substances.
2.	It occurs in plants. During day time carbon dioxide is taken in and oxygen is given out.	It occurs in all living organisms. This process occur all the time in which oxygen is taken in and carbon dioxide is given out.
3.	Light energy and chlorophyll are required.	Light energy and chlorophyll are not required.

Q.4: Define Stomata? OR What are stomata? What function do they perform in photosynthesis?
Ans: Stomato (Singular “Stomo’ means ‘mouth):
There are microscopic openings present in the epidermis of leaves called stomata. Through these openings, plants exchange gases with their environment. Each stoma is a slit-like opening formed by two special cells called guard cells. They are chlorophyll containing cells with thicker inner while thinner and elastic outer cell walls. The opening and closing of stomata depend upon the turgidity of the guard cells.

Function Of Stomata In Photosynthesis Process:
During the daytime, as a result of the ongoing process of photosynthesis, the accumulation of photosynthetic solutes causes an increase in turgidity of the guard cells. Thus stomata are opened and the process of taking in carbon dioxide and giving out of oxygen begins until it becomes dark.

Q.5: Describe gaseous exchange in animals?
Ans: Gaseous Exchange In Animals:
Animal do exchange gases with their environment for the respiration process. To obtain energy from food, they take in oxygen and give out carbon dioxide. So, the process of gaseous exchange is ultimately linked with respiration.
The respiratory medium for aquatic animals is water whereas for terrestrial animals is air. The amount of molecular oxygen present in the air is about 21% while in water it is about 5%.

Q.6: What is respiratory surface? Write its properties and also describe proportion of the respiratory surface in animals?
Ans: Respiratory Surface:
Respiratory surface is the area where gaseous exchange occurs in body. Examples gills, trachea, lungs etc.
To exchange gases, animals have respiratory surface. In unicellular organisms like Protozoa, the plasma membrane serves as the respiratory surface. In multicellular animals, the body surface or some internal surface could serve as the respiratory surface.

Properties of Respiratory surface In Animals:

• Thin
• Wet
• Permeable
• Large in relation to the volume of the body.

The Proportion Of Respiratory Surface In Animals:
It must be sufficient large enough for exchange gases for all the cells of the body. For example, the total surface area of the respiratory surface in humans is about 20 times the size of the body.

Q.7: What are the effects of large respiratory surfaces in animals?
Ans: Effects Of Large Respiratory Surfaces In Animals:
An increased surface for gaseous exchange allows a faster rate of diffusion to supply oxygen and remove carbon dioxide It is also necessary to compensate for the small surface area to volume ratio of the animal body.

Q.8: How many processes are involved in human respiration?
Ans: Processes Involved In Human Respiration:
In human, the process of respiration involves:

• breathing,
• gaseous exchange and
• cellular respiration

Like other terrestrial vertebrates, our respiratory surface is located inside the body in the form of alveoli contained in paired organs, lungs.

Q.9: Define respiratory system? Describe the human respiratory system in detail? Also draw well-labeled diagram Of human respiratory system?
Ans: Respiratory System:
The system which is responsible for the exchange of gases (oxygen is taken in and carbon dioxide is given out) between the body and the environment is called respiratory system.

Human Respiratory System:
Our respiratory system consists of:

• Paired lungs located inside the thoracic (chest) cavity and
• Air passageways

LUNGS:

• There is a pair of lungs present in the chest cavity in man. Each lung is soft, spongy and pinkish in appearance.
• Pleural membranes: Lungs are wrapped in two Pleural membranes. The space between pleural membranes is filled with fluid that acts as a lubricant. This watery fluid makes the movements of the lungs (expansion and contraction) easy. This makes breathing movements easier. It also protects the lungs from external injuries.
• Lungs are enclosed in a protected bony cage made up of a flat sternum in front, 12 pairs of ribs from front to back where the vertebral column is present.
• Ribs are attached with intercostal muscles.
• Diaphragm: In the lower part of the thorax, lies a sheet of muscles called Diaphragm which separates it from the abdominal cavity.
• Each lung is made up of millions of alveoli.
  

Lung Capacity:
Like a balloon, lungs can be filled with a maximum amount of 5 liters of air. Surprising, we use normal about ¹/₂ of the air coming into the lungs.

Alveoli:
The walls of the respiratory bronchioles have clusters of tiny air sacs are called alveoli (singular: alveolus). Each alveolus is the respiratory surface. It's a pouch-like microscopic structure made up of only one layer of cells. It's enclosed by a dense capillary network. In each alveolus, the exchange of gases takes place between air and blood through capillary network.



THE AIR PASSAGEWAY:
The air passageway consists of:

• Nose (Nostril)
• Pharynx
• Larynx
• Trachea
• Bronchi and
• Bronchioles
  

This entire passage through which air passes is lined by mucous secreting ciliated cells. The internal surface has rich blood capillaries which turn the incoming air slightly hot.

 Nose (Nostril):

• Air from outside enters into the nasal sacs through external nostrils. 
• The hairs in nasal sacs as well as ciliated epithelial lining and mucous keep the air cleans by trapping and removing dust and germs. This ensures clean air approach the respiratory surface.
• In this way air is purified and is then pushed into the pharynx.
  
  

Pharynx:

• The nasal cavity opens into the pharynx (throat) through two small apertures which are called internal nostrils.
• The pharynx is muscular passage which extends from behind the nasal cavities to the opening of esophagus and larynx.
• The air goes from the pharynx into the larynx.

Larynx:

• At the beginning of trachea, there is a cartilaginous box called larynx or sound box, containing vocal cords to produce sound.
• Glottis: The opening of the larynx is known as glottis.
• Epiglottis: Glottis has a lid like cover, epiglottis. During swallowing food or drink, the epiglottis closes the glottis to prevent any food to enter the trachea.

Trachea:

• Larynx opens into a long tube air tube (wind pipe) called Trachea.
• It is about 12 cm long and lies in front of the oesophagus.
• The trachea has incomplete C-shaped cartilaginous rings which prevent it from collapsing and thus keep the air passage wide open all the time.
• Trachea is also lined with ciliated mucous epithelium. Any foreign particles present in the inhaling air get trapped in the mucous that is moved out of the trachea by breathing of the cilia in the upward direction.
• In trachea air is further cleansed and filtered and then moved towards the lungs.

Bronchi:

• Trachea in the center of the thorax bifurcates into two smaller ducts or Bronchi. Each bronchus have C-shaped cartilaginous rings.
• The bronchus of each side enters into the respective lung. As soon as enters into the lung, it breaks up into many smaller ducts or bronchioles.
• The right bronchus divides into three secondary bronchi and the left bronchus divides into two secondary bronchi which serve the 3 right and 2 left lobes of the lungs respectively.

Bronchiole:

• The secondary bronchi further divide into very fine and thin branches (tubes) called bronchioles.
• The bronchioles do not have cartilaginous plates in their walls. They have smooth muscle and elastic fibers.
• Each bronchiole opens into air sacs or alveoli.

OR

Q.10: Explain the process of ventilation or breathing in man?
Ans: Ventilation or Breathing:
Ventilation or breathing is largely involuntary process, It is regulated by hypothalamus of our brain. It is the movement of air through the conducting passages between the atmosphere and the lungs. The air moves through the passage because of pressure gradient that are produced by the contraction of the diaphragm and thoracic muscles.
Pulmonary respiration is commonly referred to as breathing. It is the process of air flowing into the lungs during inspiration (inhalation of oxygen from the environment) and air flowing out of the lungs during expiration (exhalation of carbon dioxide back into environment). Air flows because of pressure differences between the atmosphere and the gases inside the lungs.

Process of Breathing:
The respiratory surfaces are located deep inside the body in the lungs. So in order to perform the exchange of gases, the air must first be brought into the lungs from the atmosphere. It is achieved through the process of breathing or ventilation. The process of breathing consists of two phases:

1. Inspiration Or Inhalation and
2. Expiration Or Exhalation
   
   

Inspiration Or Inhalation:

• It is the process through which atmospheric air is directed through the air passageways up to the alveoli in the lungs. It involves the contraction of:
  * external intercostal muscles that raising the rib-cage and
  * the diaphragm that becomes flattened by lowering the floor of the thoracic cavity.
• As a result, the volume of the thorax (chest) is increased thereby decreasing the pressure of air within the lungs.
• So the external air rushes inside from high pressure to low pressure. The lungs gets expanded in this way.

Expiration Or Exhalation:

• It is just the reverse of inspiration. During this process, the air moves out from the lungs.
• Both, intercostal muscles and diaphragm are relaxed. This moves the ribs inside and the diaphragm resume dome like shape.
• Both the activities depress the chest inside. The volume of the thoracic cavity (chest) is decreased causing an increase in the pressure on the lungs.
• This forces the air present in the lungs to outside through the body.

OR

Q.11: Briefly describe the gaseous exchange in alveoli?
Ans: Gaseous Exchange in Alveoli:
The gaseous exchange takes place at the level of alveoli. Oxygen brought in by air is taken up by the haemoglobin of RBCs of blood and vice versa. The carbon dioxide brought by the blood is given out to the air present in alveoli. This gaseous exchange involves diffusion which becomes possible at this level because both alveolus ad blood capillaries are only one cell layer in thickness.

Q.12: Write down the composition of inspired and expired air?
Ans: Composition Of Inspired and Expired Air:

Components %	Inspired Air	Expired Air
Oxygen	About 61	About 16
Carbon dioxide	About 0.03	About 4
Nitrogen	About 79	About 79
Water Vapour	Variable	Saturated
Temperature	Atmospheric temperature	37 degree Celsius

Q.13: Prove with the help of experiment that CO₂ is released during respiration. OR How can we demonstrate the release of carbon dioxide during expiration?
Ans: CO₂ Is Released During Respiration:

Principal Theory:

• Respiration is a chemical reaction which releases energy from food. The respiratory system exchanges the gases which are involved in respiration.
• Respiration by living organisms can be investigated by carrying out experiments to show the production of carbon dioxide and heat.
• Lime water can be used to detect carbon dioxide.
• If carbon dioxide is bubbled through lime water then it turns from clear to cloudy/milky in colour. That is why lime water is used in a simple respirometer, which can show that more carbon dioxide is present in exhaled air compared to inhaled air.

Material Required:

• Respirometer (Cork, Glass tubes and Test tube)
• Syringe
• Lime water

Procedure:

• To prepare respirometer, pass two glass tubes through cork.
• Fix the cork at the mouth of test tubes containing lime water.
• Prepare two apparatus and marked as (A) and (B)
• In (A) respirometer exhaled air through Glass tube into lime water
• In (B) respirometer pass atmospheric air by syringe through Glass tube into lime water.

Observation
Carbon dioxide if passed through lime water turns it milky. This is evident through experiment as:

• (A) when exhaled air passes through the respirometer apparatus containing lime water, the lime water turns milky.
• In (B) when atmospheric air is passed through respirometer apparatus containing the lime-water , the later remains unchanged,
  
  

Conclusion:
Exhaled air contain more carbon dioxide than inhaled air.

Q.14: Distinguish between inspiration and expiration.
Ans: Difference Between Inspiration And Expiration

S.NO.	INSPIRATION	EXPIRATION
1.	Inspiration is the intake of the air (oxygen) into the lungs.	Expiration is the expulsion of the air (carbon dioxide) out of the lungs.
2.	Inspiration is an active process.	Expiration is a passive process.
3.	The external intercostals muscles are contracted and internal intercostals muscles are relaxed.	The external intercostals muscles are relaxed and internal intercostals muscles are contracted.
4.	Rib cage moves forward and outward.	Rib cage moves downward and inward.
5.	The diaphragm moves down by contracting and become flat.	The diaphragm moves up by relaxing and becomes original dome shaped.
6.	The size of the thoracic cavity increases.	The size of the thoracic cavity decreases.
7.	The air pressure inside the lungs decreases due to the increase of volume of the chest cavity.	The air pressure inside the lungs increases due to the decrease of volume of the chest cavity.
8.	This process is also called inhalation.	This process is also called exhalation.

Q.15: Why do we deep breathe during or immediately after exercise? Or Why rate of breathing change with different conditions? OR What will be the rate of breathing at rest or during exercise?
Ans: We deep breathe during and immediately after exercise because the rate of breathing changes automatically according to the changes in internal or external conditions.
Breathing is largely an involuntary process. It is regulated by hypothalamus of our brain. When we are doing exercise our muscles work harder, rate of breathing would increase because of increased consumption of oxygen by our muscles. Thus gradually increase in concentration of carbon dioxide in our blood will cause an increase our breathing rate.
If the exercise condition persists, the muscle cells will start breaking down glucose without oxygen. It is termed as "anaerobic respiration". As a result of this, lactic acid is formed in the muscles rather than carbon dioxide. It causes pain and cramps in normal muscles. The breaking down of lactic acid requires additional amount of oxygen. The extra amount of oxygen is obtained through deep breathes.

Q.16: Define oxygen debt?
Ans: Oxygen Debt:
During exercise, the muscle cells start breaking down glucose without oxygen. As a result of this , lactic acid is formed in the muscles rather than carbon dioxide. The breaking down of lactic acid requires additional amount of oxygen. That extra amount is called oxygen debt and is obtained through deep breathes.

OR

A temporary oxygen shortage in the body tissues arising from exercise. In this condition break down of lactic acid requires additional amount of oxygen which is termed as "oxygen debt". The extra amount of oxygen is obtained through deep breathes.

Q.17: What is artificial ventilator? Illustrate its process?
Ans: Artificial ventilator:
It is a machine that works like lungs when patient's natural breathing becomes difficult. Through this machine, the oxygen rich air is directly supplied to the trachea through a tube inserted in the mouth up to the windpipe.

Process Of Artificial Ventilator:

Q.18: Describe respiratory disorder?
Ans: RESPIRATORY DISORDERS Or DISORDERS OF RESPIRATORY SYSTEM:
1. BRONCHITIS: This is a type of COPD. The long-term (chronic) inflammation of the air passageways is termed as Bronchitis.
Cause: It is caused either by smoking or by some bacteria.
Symptoms: It is characterized by cough, increased mucous secretion, shortness of breath and low fever.
Treatment: Bronchitis is treated by using antibiotics, bronchodilator oxygen therapy and anti-inflammatory drugs.

2. EMPHYSEMA: This is also a type of COPD. It is related to the progressive destruction to the alveoli.
Cause: It occur due to long term exposure usually to the industrial pollutants or smoking.
Symptoms: It is characterized by laborious breathing. It causes cough with phlegm production and extreme tiredness (fatigue). It can also cause sleeping and heart problems, weight loss and depression.
Treatment: Its effect is permanent and irreversible however if a person is stop smoking soon, further damage might be reduced.

3. PNEUMONIA: It is an infectious disease.
Cause: It usually caused by special bacteria, viruses or fungi.
Symptoms: In pneumonia, the alveoli are infected so they may be filled with fluid or pus. The breathing becomes difficult. The patient suffers from fever, cough, chill and chest pain.
Treatment: Antibiotics are used for its treatment.

4. ASTHMA: It is an inflammatory condition of airways of lungs.
Cause: Asthma is actually an allergic response to pollen dust, smoke, fur, feathers and number of other substances. It may obstruct the airways making it difficult to breath for its patient.
Symptoms: It is characterized by shortness of breath, chest pain, fever, wheezing sound during expiration and cough.
Treatment: It can be treated by using cough syrups, anti-inflammatory drugs, allergy medication and bronchodilators.

5. LUNG CANCER: Lung cancer is a respiratory disease, more common in men than women. In it abnormal cells appear in lungs which may spread to other tissues. It can cause lumps, masses or tumors to grow in the lungs. It may start in the lining of the bronchi or it may be in other areas of the lungs.
Causes: Smoking, Industrial carcinogens, Air pollution.
Main cause of any cancer is a carcinogen, ionizing radiation, and viral infection. Smoking is the main contributor to lung cancer. Cigarette smoke contains over 69 known carcinogens.
Symptoms: Cough with sputum and blood, breathlessness (shortness of breath), pleural chest pain, repeated lung infections, weight loss, bone ache, hoarseness, weakness, fatigue etc.
In the early stages, lung cancer does not show any symptoms. However, in the advanced stage when it has fully spread, it is very painful and incurable and becomes fatal.
Other Types Of Cancer: Smoking increases the risk of the nose, sinuses, voice box and throat. It also increases the risk of many other cancers like cancer of gastrointestinal, urinary and female reproductive system.
Treatment: The patient of lung cancer is given one or more treatments, including: surgery, chemotherapy and radiation.

Q.19: Define Guard cell?
Ans: Guard Cells:
Each stoma is formed by two special cells called guard cells. They are chlorophyll containing cells with thicker inner while thinner and elastic outer cell walls. The opening and closing of stomata depend upon the turgidity of the guard cells.

Q.20: Give the death ratio due to air pollution?
Ans : Death Ratio Due To Air Pollution:

PRACTICAL ACTIVITY

Q.21: Explain the effect of light on the net gaseous exchange from leaf by using Hydrogen bicarbonate as indicator through experiment.
Theory:
Hydrogen bicarbonate is an indicator for carbon dioxide. Its colour turns as follows according to the level of carbon dioxide:

Photosynthesis	Respiration
Highest	Yellow
High	Orange
Atmospheric level	Red
Low	Magenta
Lowest	Purple

Requirements:

• Four test tubes
• Test tube stand
• Aluminum foils or black paper
• Tissue paper
• Fresh green leaves
• Four corks
• Wax
• Thread
• Glass marking
• Pencil

Steps:

1. Mark test tubes as 1, 2, 3 and 4.
2. Fill each test tube quarter full with Hydrogen bicarbonate indicator.
3. Attach each leaf with separate thread and hang one into the test tube 1, test tube 2 and test tube 3.
4. Plug all the tubes with corks and seal them with wax.
5. Wrap tube 2 with aluminum foil or black paper from all side so that light cannot penetrate into this test tube. Similarly wrap test tube 3 with tissue paper.
6. Place all tubes on stand and put the stand in well lighted place.
7. Note and record your observations given below in the table by tick marking the right in the following table:

Observations:

Critical Thinking:
(i) Is there any change of coloration of Hydrogen bicarbonate indicator?
Ans: Yes, Hydrogen bicarbonate is an indicator for carbon dioxide. Its colour turns as follows according to the level of carbon dioxide.

Concentration Of CO2	Colour Of Hydrogen bicarbonate
Highest	Yellow
High	Orange
Atmospheric level	Red
Low	Magenta
Lowest	Purple

(ii) What account for these changes?
Ans: The change in colour of Hydrogen bicarbonate indicator with the different levels of carbon dioxide shows that:
During daytime in the presence of light, when photosynthesis process occurs the concentration of carbon dioxide is lowest because the amount of CO₂ absorbs by plant is greater than the amount of carbon dioxide release during respiration.
While at night in the absence of light only respiration process takes place, so the concentration of carbon dioxide is higher.

Source: Special Thanks To Sir Syed Arif Ali