The Respiratory System

Progress Check 1

Question 1

Given below is the definition of respiration with a few blanks to be filled in. Write suitable words in the blanks:

Respiration is a process of releasing ............... by breaking down ............... for carrying out ............... processes.

Answer

Respiration is a process of releasing energy by breaking down glucose for carrying out life processes.

Question 2

Write the overall chemical equation representing the above definition of respiration.

Answer

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \xrightarrow{\text{enzymes}} 6\text{CO}_2 + 6\text{H}_2\text{O} + \underset{\text{chemical energy}}{38 \text{ ATP}} + \underset{\text{heat energy}}{420 \text{ kcal}}$

Question 3

In what form is the energy liberated in respiration?

Answer

The energy liberated in respiration is in the form of ATP (adenosine triphosphate).

Question 4

Give two examples of life activities which need energy.

Answer

1. Synthesis of proteins from amino acids
2. Production of enzymes

Progress Check 2

Question 1

State whether the following statements are true (T) or false (F):

1. Strenuous physical exercise may cause fatigue due to accumulation of CO₂ in the blood.
2. No CO₂ is produced in anaerobic respiration in the human body.
3. Breathing and gaseous transport are one and the same thing.
4. CO₂ is transported to the lungs by the blood in two forms: as bicarbonates and as carbamino-haemoglobin.
5. Tissue respiration means chemical changes occurring inside the cell.

Answer

1. False
   Corrected Statement— Strenuous physical exercise may cause fatigue due to accumulation of lactic acid.
2. True
3. False
   Corrected Statement— Breathing and gaseous transport are first two steps of the four step respiration process in humans and animals.
4. True
5. False
   Corrected Statement— Cellular respiration means chemical changes occurring inside the cell.

Progress Check 3

Question 1

Match the items in Column I with those in Column II

Answer

Question 2

How do the following contribute in inspiration during breathing?

1. Ribs
2. Diaphragm

Answer

1. During inhalation, the ribs move upwards and outwards due to contraction of the external intercostal muscles stretched between them. This enlarges the chest cavity.
2. The diaphragm flattens, expanding the chest cavity lengthwise. This increases the volume and decreases the pressure inside the lungs. Air is then drawn in from outside to equalize the pressure.

Question 3

Match the lung capacities in Column I with the quantities given in Column II.

Answer

Progress Check 4

Question 1

Mention any two points of difference in the quality of inspired and expired air.

Answer

Question 2

Give reasons for:

1. People climbing to high altitudes may suffer from dizziness and unsteady vision.
2. Lime water is used in most experiments on respiration.
3. Respiration rate is higher in animals than in plants.

Answer

1. At higher altitudes, the density of air is less and amount of oxygen is also less. This causes deficiency of oxygen in the body which further results in dizziness and unsteady vision.
2. Lime water is used in most experiments on respiration as lime water turns milky when it comes in contact with carbon dioxide. It is thus an easy way to detect carbon dioxide.
3. Animals lead an active life where physical movement is involved and have complex organ systems that require constant energy supply. Hence, respiration rate is higher in animals than in plants to meet the higher energy requirements.

Question 3

Given along side is an experiment intended to demonstrate the action of diaphragm, but some thing has gone wrong.

What is the mistake in the diagram? Explain.

Answer

The mistake in the diagram is that the balloons are expanded and air is rushing in when the rubber sheet is pushed upwards. In the correct experiment, when the sheet is pushed upward, the volume is decreased, pressure inside the jar increases and balloons collapse due to air rushing out.

Multiple Choice Type

Question 1

During inspiration, the diaphragm

1. Relaxes
2. Contracts
3. Expands
4. Gets folded

Answer

Contracts

Reason — During inspiration, the chest is expanded and the diaphragm contracts.

Question 2

The ultimate end parts of the respiratory system in humans are known as

1. Alveoli
2. Bronchioles
3. Tracheoles
4. Bronchi

Answer

Alveoli

Reason — Alveoli is the part of respiratory system where the gaseous exchange occurs.

Question 3

During respiration there is

1. Gain in dry weight
2. Loss in dry weight
3. No change in dry weight
4. Increase in the overall weight

Answer

Loss in dry weight

Reason — Respiration burns glucose to form carbon dioxide (which escapes) and releases energy. This leads to loss in dry weight.

Question 4

The product of anaerobic respiration in animals is:

1. Amino acids
2. Uric acid
3. Lactic acid
4. Ethanol

Answer

Lactic acid

Reason — The product of anaerobic respiration in animals is lactic acid. No CO₂ is produced.

Question 5

Anaerobic respiration in animals mostly occurs in:

1. Cardiac muscles
2. Skeletal muscles
3. Both (i) and (ii)
4. Smooth muscles

Answer

Skeletal muscles

Reason — Anaerobic respiration in animals mostly occurs in skeletal muscles when they have to work very fast with insufficient oxygen.

Question 6

Which of the following is popularly called as Adam's apple ?

1. Larynx
2. Glottis
3. Pharynx
4. Epiglottis

Answer

Larynx

Reason — Larynx or voice box is called as Adam's apple.

Question 7

The basic structural and functional unit of a lung is

1. Capillaries
2. Alveolus
3. Bronchioles
4. Bronchi

Answer

Alveolus

Reason — Alveolus is the basic structural and functional unit of a lung as the gaseous exchange occurs in alveolus.

Question 8

The protective membranous covering of lung is:

1. Capsule
2. Pericardium
3. Epithelium
4. Pleura

Answer

Pleura

Reason — The lungs are protected by pleural membrane and pleural fluid.

Question 9

The muscular sheet which separates the thoracic and abdominal chamber of the human body is:

1. Peritoneum
2. Diaphragm
3. Parietal pleura
4. Visceral pleura

Answer

Diaphragm

Reason — The muscular sheet which separates the thoracic and abdominal chamber of the human body is Diaphragm.

Question 10

Which of the following produces mucus in the respiratory passage?

1. Ciliated cells
2. Air sacs
3. Goblet cells
4. Tertiary bronchi

Answer

Goblet cells

Reason — Goblet cells make mucus which traps dust particles.

Very Short Answer Type

Question 1

Name the following :

(a) The energy currency of the cell.

(b) The compound formed by the combination of oxygen and haemoglobin.

(c) The common passage of Oesophagus and Trachea.

(d) The muscles found between the ribs which can change the size of the chest cavity lengthwise.

(e) The compound formed by the combination of haemoglobin and carbon dioxide gas.

Answer

(a) ATP

(b) Oxy-haemoglobin

(c) Pharynx

(d) Diaphragm

(e) Carbamino-haemoglobin

Question 2

Name the body structure concerned with the given functional activity:

(a) Prevents food from entering the trachea during swallowing.

(b) Transports oxygen to the body cells.

(c) Helps to increase the volume of the chest activity lengthwise.

(d) Combines with the oxygen in the lungs.

(e) Protects the lungs from mechanical injuries.

(f) Provides actual diffusion of respiratory gases in lungs.

Answer

(a) Epiglottis

(b) Capillaries

(c) Diaphragm

(d) Bronchioles

(e) Ribs

(f) Air sacs / Alveoli

Question 3

Name:

(a) Two kinds of respiration

(b) Two steps of cellular respiration

(c) Two phases of breathing

(d) Two main raw materials for respiration

(e) Two parts of tidal volume

Answer

(a) Aerobic respiration and Anaerobic respiration

(b) Glycosis and Krebs Cycle

(c) Inhalation and Exhalation

(d) Glucose and Oxygen

(e) Dead Air space (150 ml) and Alveolar air (350 ml)

Question 4

Arrange the organs of the human respiratory system in a proper logical sequence:

Bronchi, Lungs, Larynx, Nose, Trachea, Pharynx.

Answer

Nose → Pharynx → Larynx → Trachea → Bronchi → Lungs

Question 5

What is the normal percentage composition of gases in inspired air and expired air respectively?

Answer

The following table depicts the gas composition in percentage:

Question 6

Match the items in Column I with the ones most appropriate in Column II. Rewrite the matching pairs:

Answer

Short Answer Type

Question 1

Given below is an example of a certain structure and its special functional activity:

"Kidney and excretion"

Fill in the blanks on a similar pattern.

(a) Alveoli and ...............

(b) Mitochondria and ...............

(c) Epiglottis and ...............

(d) Pleura and ...............

(e) Diaphragm and ...............

(f) 'C' shaped cartilage rings and ...............

Answer

(a) Alveoli and gaseous diffusion.

(b) Mitochondria and cellular respiration.

(c) Epiglottis and swallowing food.

(d) Pleura and protection of the lungs.

(e) Diaphragm and breathing.

(f) 'C' shaped cartilage rings and support and strengthen trachea.

Question 2

Match the items in Column A with those in Column B.

Answer

Question 3

State one function of each of the following:

(a) Ciliated epithelium lining the respiratory tract

(b) Mitochondria

(c) Diaphragm

(d) Intercostal muscles

(e) Pleural fluid

Answer

(a) Ciliated epithelium lining the respiratory tract — The entire lining of the larynx, trachea, bronchi and bronchioles is formed of ciliated epithelium. It is the protective inner lining of the respiratory passage. It helps in motion, driving any fluid that is on them.

(b) Mitochondria — In mitochondria, pyruvic acid is further broken down step by step in a cyclic manner in the presence of oxygen.

(c) Diaphragm — Diaphragm contributes to the enlargement of the chest cavity lengthwise.

(d) Intercostal muscles — The muscles help the inward and outward movement of ribs enlarging the chest cavity all around.

(e) Pleural fluid — It provides lubrication for free movement of the contracting and expanding lungs.

Question 4

Under what conditions would the breathing rate increase?

Answer

Breathing rate can increase under the following circumstances:

1. Accumulation of carbon dioxide in blood.
2. Vigorous physical exercise.

Question 5

How would you prove that the air you breathe out is warmer?

Answer

During breathing, the air expelled out is always warmer or at the body temperature. It can be felt by breathing out the air on our own hand. One can feel the warmth of the air expelled out during breathing.

Question 6

How is the respiratory passage kept free of dust particles?

Answer

The nasal cavity is lined by ciliated epithelium and mucous glands. The mucous glands secrete mucous. The ciliated epithelium is present on the entire lining of the trachea, larynx, bronchioles and bronchi. The constant motion of cilia and mucous trap dust, micro-organisms, pollen and other minute particles present in the air. In this way, the respiratory passage is kept free of dust particles.

Question 7

What is wrong in the statement "We breathe in oxygen and breathe out carbon dioxide"?

Answer

We inhale air containing much oxygen and very little carbon dioxide and exhale air containing less of oxygen and more of carbon dioxide. Therefore, the statement “We breathe in oxygen and breathe out carbon dioxide” is wrong.

Question 8

Write the balanced chemical equations for the following:

(a) Aerobic respiration

(b) Anaerobic respiration in plants

(c) Anaerobic respiration in animals

(d) Photosynthesis

(e) Phosphorylation

Answer

(a) Aerobic respiration
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP + 420 kcal

(b) Anaerobic respiration in plants
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2ATP

(c) Anaerobic respiration in animals
C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid) + 2ATP

(d) Photosynthesis
6CO₂ + 12H₂O $\xrightarrow[\text{chlorophyll}]{\text{sunlight}}$ C₆H₁₂O₆ + 6H₂O + 6O₂↑

(e) Phosphorylation
ADP + P_i (inorganic phosphate) → ATP

Question 9

Define:

(a) Respiration

(b) Hypoxia

(c) Asphyxiation

(d) Breathing

(e) Vital capacity

Answer

(a) Respiration — Respiration is the biochemical process of releasing energy by breaking down glucose for carrying out life processes.

(b) Hypoxia — Hypoxia is the deficiency of oxygen reaching the tissue. It may occur due to over crowding with poor ventilation or at high altitudes.

(c) Asphyxiation — Asphyxiation is a condition in which the blood becomes more venous by accumulation of more carbon dioxide and the oxygen supply is diminished.

(d) Breathing — Breathing is a physical process in which the atmospheric air is taken in and forced out of the oxygen-absorbing organs, the lungs.

(e) Vital capacity — Vital Capacity is defined as the volume of air that can be taken in and expelled out by maximum inspiration and expiration. It is 4500 ml.

Long Answer Type

Question 1

Differentiate between the following pairs on the basis of the aspect given in the brackets.

(a) Aerobic and anaerobic respiration (end products of the process)

(b) Respiration and photosynthesis (gas released)

(c) Photosynthesis and respiration (reactants)

(d) Respiration and breathing (organs involved)

(e) Tidal volume and residual volume (quantity of air)

Answer

(a) Aerobic and anaerobic respiration (end products of the process)

(b) Respiration and photosynthesis (gas released)

(c) Photosynthesis and respiration (reactants)

(d) Respiration and breathing (organs involved)

(e) Tidal volume and residual volume (quantity of air)

Question 2

Give suitable explanations for the following:

(a) Breathing through the nose is said to be healthier than through the mouth.

(b) Why does gaseous exchange continue in the lungs even during expiration?

(c) Why does a person feel breathlessness at higher altitudes?

(d) Why do you shiver and why do your teeth chatter when it is very cold in winter?

Answer

(a) Breathing through the nose is said to be healthier than through the mouth because the external part of the nose bears two nostrils separated by a cartilaginous septum. The hairs present in the nostrils prevent large particles from entering the respiratory system. So, always breathe through the nose and not through the mouth.

(b) Gaseous exchange continue in the lungs even during expiration because expiration is the result of reverse movements of the ribs and diaphragm. As a result of the movements of the ribs and the diaphragm, the thoracic cavity is diminished and the lungs are compressed, forcing the air out into the atmosphere.

(c) A person feel breathlessness at higher altitudes because as we go higher up, the air we breathe in decreases in pressure accompanied by a gradual decrease in oxygen content.

(d) We shiver and our teeth chatter when it is very cold in winter in order to increase the heat production in the body. To maintain the temperature of the body constant in extremely cold conditions, the production of heat is increased through heightened metabolic rate and greater muscular activity and shivering and teeth chattering involves a lot of muscular activity.

Question 3

With regard to the respiratory system and the process of respiration in man, answer the following questions:

(a) Name the two muscles that help in breathing.

(b) Briefly describe how the above mentioned muscles help in the inspiration of air.

(c) Give the overall chemical equation to represent the process of respiration in humans.

(d) What is meant by:

1. Residual air
2. Dead air space

Answer

(a) The two muscles that help in breathing are — intercostal muscles and abdominal muscles.

(b) When the intercostal muscles stretch between the ribs, they move outwards and inwards causing them to enlarge the chest cavity.

(c) The overall chemical equation for the process of respiration in humans is as given below:

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \xrightarrow{\text{enzymes}} 6\text{CO}_2 + 6\text{H}_2\text{O} + \underset{\text{chemical energy}}{38 \text{ ATP}} + \underset{\text{heat energy}}{420 \text{ kcal}}$

(d) The meanings of Residual air and Dead air space are as follows:

1. Residual Air — Even after forcibly breathing out, some air always remains in the lungs. This air is referred to as residual air. The volume of this air is 1500mL.
2. Dead air space — Some tidal air is remaining in the respiratory passages such as bronchi and trachea. Here no gas diffusion takes place. This volume is referred to as dead air space and its volume is 150mL.

Question 4

Starting from the nostrils, trace the path in sequence which the transpired air takes until it reaches the air sacs.

Answer

The path taken by the transpired air through the nostrils until it reaches the air sacs is as follows:

Nose → Pharynx → Larynx → Trachea → Bronchi

Question 5

What are the functions of the following in breathing?

(a) Ribs

(b) Diaphragm

(c) Abdominal muscles

Answer

(a) Ribs — The ribs move upwards and outwards due to the contraction of the external intercostal muscles stretched between them thus enlarging the chest cavity all around. (The internal intercostal muscles are relaxed).

(b) Diaphragm — The diaphragm contracts and flattens from the dome shaped outline to an almost horizontal plane and thus contributes to the enlargement of the chest cavity lengthwise.

(c) Abdominal muscles — It helps to increase the size of the thoracic cavity through the motion of the diaphragm which assists in inspiration.

Structured / Application / Skill Type

Question 1

Given alongside is a diagrammatic sketch of a part in human lungs

(i) Name the parts numbered 1-4

(ii) What do the arrows 5 and 6 indicate?

Answer

(i) The parts numbered 1-4 are:

• 1 → Thin walls of capillary
• 2 → Red blood corpuscles
• 3 → Plasma
• 4 → Thin wall of alveoli

(ii) Arrows at 5 & 6 indicate diffusion of carbon dioxide outside and diffusion of oxygen inside respectively.

Question 2

Given below is an overall chemical reaction of a certain process:

C₆H₁₂O₆ → lactic acid + 2ATP + heat energy

(a) Name the process.

(b) Is this reaction applicable to animals or to plants or to both animals and plants?

(c) Name one tissue in which this reaction may occur.

Answer

(a) The process is anaerobic respiration.

(b) The reaction is applicable to animals only.

(c) The reaction may occur in skeletal muscular tissues.

Question 3

Given below are chemical reactions (1 to 5) involving glucose and five other chemical products (A-E).

(a) Write the reaction number of the following:

(i) Anaerobic respiration in plants ...............

(ii) End-products in aerobic respiration ...............

(iii) Reaction occurring in liver ...............

(iv) Anaerobic respiration in animals ...............

(v) Storage in the liver ...............

(b) Which reactions (1-5) in the above correspond to the following (write the corresponding number of reaction next to them).

(i) Aerobic respiration

(ii) Change taking place in the liver

(iii) Anaerobic respiration in yeast

(iv) Change taking place in a plant storage organ – e.g. potato.

(v) Anaerobic respiration in animals

Answer

(i) Anaerobic respiration in plants - 5

(ii) End-products in aerobic respiration - 4

(iii) Reaction occurring in liver - 2

(iv) Anaerobic respiration in animals - 1

(v) Storage in the liver – 3

(b) The corresponding reaction number is as follows:

(i) Aerobic respiration - 4

(ii) Change taking place in the liver - 3

(iii) Anaerobic respiration in yeast - 5

(iv) Change taking place in a plant storage organ, e.g., potato - 2

(v) Anaerobic respiration in animals - 1

Question 4

The volume of air in the lungs and the rate at which it is exchanged during inspiration and expiration was measured.

The following diagram shows a group of the lung volumes and capacities:

Study the diagram carefully and explain briefly the following:

1. Tidal volume
2. Inspiratory reserve volume
3. Expiratory reserve volume
4. Vital capacity
5. Residual volume

Answer

1. Tidal volume — It is the air breathed in and out in a normal quiet breathing. The tidal volume(TV) is 500mL.
2. Inspiratory reserve volume — Air that can be drawn in forcibly over and above the tidal air is known as inspiratory reserve volume. It is referred to as IRV or complemental air and is 3000mL.
3. Expiratory reserve volume — It is the air that can be expelled out forcibly after a normal expiration. It is referred to as ERV or supplemental air and is 1000mL.
4. Vital capacity (VC) — It is the volume of air that can be inhaled and exhaled by maximum inspiration and expiration respectively and is about 4500mL.
5. Residual volume (RV) — Even after forcible expiration, there is some air left in the lungs and is referred to as residual volume. It is about 1500mL.

Question 5

The figure given below represents a certain organ of the human chest cavity. Study the same and answer the following questions.

(a) Identify the organ and the organ system.

(b) Label the guidelines 1 to 6.

(c) What are the two advantages of C-shaped cartilaginous rings found in structure 1 ?

(d) Name the fluid filled between the two protective layers of the organ shown as part 2.

(e) Name the basic structural and functional unit of part 2.

Answer

(a) The given figure shows respiratory system and lungs.

(b) Labelled guidelines 1 to 6 are :

• 1 → Trachea
• 2 → Left lung
• 3 → Bronchus
• 4 → Rib cage
• 5 → Pleural fluid
• 6 → Diaphragm

(c) Two advantages of C-shaped cartilaginous rings of trachea are:

• Provide strength to trachea.
• Provide flexibility and keep the trachea distended permanently.

(d) Pleural fluid

(e) Alveoli

Question 6

The figure given alongside shows an experimental set up to demonstrate a process. Answer the following questions.

(a) Name the process depicted.

(b) What are the two steps of the above mentioned process?

(c) What do the following parts in the diagram represent ?

1. Balloons
2. Rubber sheet
3. Bell jar

(d) Write the exact location of the organ represented by the balloons in the human body.

Answer

(a) Breathing.

(b) Inspiration and expiration.

(c) The parts represent:

1. Lungs
2. Diaphragm
3. Chest cavity

(d) In the chest cavity, enclosed within the rib cage.