Biology Class 11 NCERT Solutions: Chapter 17 Breathing and Exchange of Gases Part 3

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Q: 11. Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?

Answer :

The oxygen dissociation curve is a graph showing the percentage saturation of oxyhaemoglobin at various partial pressures of oxygen.

The curve shows the equilibrium of oxyhaemoglobin and haemoglobin at various partial pressures.

In the lungs, the partial pressure of oxygen is high. Hence, haemoglobin binds to oxygen and forms oxyhaemoglobin.

Tissues have a low oxygen concentration. Therefore, at the tissues, oxyhaemoglobin releases oxygen to form haemoglobin.

The sigmoid shape of the dissociation curve is because of the binding of oxygen to haemoglobin. As the first oxygen molecule binds to haemoglobin, it increases the affinity for the second molecule of oxygen to bind. Subsequently, haemoglobin attracts more oxygen.

Oxygen dissociation curve

Oxygen Dissociation Curve

Q: 12. Have you heard about hypoxia? Try to gather information about it, and discuss with your friends.

Answer:

Hypoxia is a condition characterised by an inadequate or decreased supply of oxygen to the lungs. It is caused by several extrinsic factors such as reduction in , inadequate oxygen, etc. The different types of hypoxia are discussed below.

Image of the different types of hypoxia

The Different Types of Hypoxia

Hypoxemic hypoxia:

In this condition, there is a reduction in the oxygen content of blood as a result of the low partial pressure of oxygen in the arterial blood.

Anemic hypoxia:

In this condition, there is a reduction in the concentration of haemoglobin.

Stagnant or ischemic hypoxia:

In this condition, there is a deficiency in the oxygen content of blood because of poor blood circulation. It occurs when a person is exposed to cold temperature for a prolonged period of time.

Histotoxic hypoxia:

In this condition, tissues are unable to use oxygen. This occurs during carbon monoxide or cyanide poisoning.

Q: 13. Distinguish between

(A) IRV and ERV

(B) Inspiratory capacity and Expiratory capacity

(C) Vital capacity and Total lung capacity

Answer:

(A)

Q_13_A_Table of Inspiratory Reserve Volume and Expiratory Reserve Volume
Q_13_A_Table of Inspiratory reserve volume and Expiratory reserve volume

Inspiratory reserve volume

Expiratory reserve volume (ERV)

1.

It is the maximum volume of air that

Can be inhaled after a normal inspiration

1.

It is the maximum volume of air that

can be exhaled after a normal expiration.

2.

It is about in the

human lungs.

2.

It is about in the human lungs.

(B)

Q_13_B_Table of Inspiratory Capacity and Expiratory Capacity
Q_13_B_Table of Inspiratory Capacity and Expiratory Capacity

Inspiratory Capacity (IC)

Expiratory Capacity(EC)

1.

It is the volume of air that can be

inhaled after a normal expiration.

1.

It is the volume of air that can be exhaled after a normal inspiration.

2.

It includes tidal volume and inspiratory reserve volume.

2.

It includes tidal volume and expiratory

reserve volume.

(C)

Q_13_C_Table of Vital Capacity and Total Lung Capacity
Q_13_C_Table of Vital Capacity and Total lung Capacity

Vital Capacity (VC)

Total lung Capacity(TLC)

1.

It is the volume of air that can be

inhaled after a normal expiration.

1.

It is the volume of air that can be exhaled after a normal inspiration.

2.

It includes tidal volume and inspiratory reserve volume.

2.

It includes tidal volume and expiratory

reserve volume.

Q: 14. What is Tidal volume? Find out the Tidal volume (approximate value) for a healthy human in an hour.

Answer

Tidal volume is the volume of air inspired or expired during normal respiration.

Image shows the tidal volume

Image Shows the Tidal Volume

It is about of air per minute.

The hourly tidal volume for a healthy human can be calculated as:

Tidal volume in an hour

Therefore, the hourly tidal volume for a healthy human is approximately

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