Discuss the transport of gases (O 2 and CO 2 ) in the blood.

The transport of O 2 and CO 2 happens through blood. The RBC in the blood carry 97% of O 2 while plasma carries the remaining 3% of O 2 in a dissolved state. In case of CO 2 the RBC carry about 20-25%, plasma carries 7% of CO 2 in a dissolved state while the remaining 70% is carried as bicarbonate. Transport Of Oxygen: O 2 binds reversibly to haemoglobin in blood to give oxyhaemoglobin. Haemoglobin is a red coloured pigment in the RBC that contains iron. A maximum of molecules of O 2 can bind to a molecule of haemoglobin. The partial pressure of O 2 is the primary factor that affects this binding. Other factors that can influence this binding are partial pressure of CO 2 temperature and hydrogen ion concentration. In the alveoli, there is high pO 2 low pCO 2 low temperature, and low H + concentration. These conditions are favourable for the formation of oxyhaemoglobin. However, in the tissues, there is low pO 2 high pCO 2 high temperature, and high H + concentration which is favourable for the dissociation of O 2 from oxyhaemoglobin. This shows that O 2 binds to haemoglobin on the lung surface and gets dissociated in the tissues. Under normal physiological conditions, every 100ml of oxygenated blood delivers about 5ml of O 2 to the tissues. Transport of carbon dioxide: Apart from O 2 ,haemoglobin also carries about 20-25% of CO 2 , as carbamino-haemoglobin. This binding is primarily related to the partial pressure of CO 2 , however, pO 2 is also a major factor that affects this binding. In the tissues, when the pCO 2 is high and pO 2 is low, more binding of CO 2 takes place. On the other hand, when pCO 2 is low and pO 2 is high in the alveoli, CO 2 dissociates from carbamino-haemoglobin formed in the tissues and is released in the alveoli. The enzyme carbonic anhydrase is present in high concentration in the RBC. Small amounts of this enzyme are also present in plasma. This enzyme catalyses the following reaction in both directions: C O 2 + H 2 O ⇔ H 2 C O 3 ⇔ H C O 3 – + H + The partial pressure of CO 2 is high in the tissues due to catabolism. Here, CO 2 diffuses into the blood (plasma and RBC) and gives rise to HCO 3– and H + . The reaction takes place in the opposite direction in the alveoli where the pCO 2 is low, leading to the formation of CO 2 and H 2 O. Thus, at the tissue level, CO 2 is trapped as bicarbonate, transported to the alveoli and released as CO 2 . Under normal physiological conditions, every 100ml of deoxygenated blood delivers about 4 ml of CO 2 to the alveoli.

E M B I B E

TRUEMAN'S ELEMENTARY BIOLOGY VOL. I For XI Class of 10+2>Chapter 21 - Breathing and Exchange of Gases>TEST QUESTIONS>Q 2

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How does respiration fulfil the energy requirement of an organism.

Important Questions on Breathing and Exchange of Gases

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TRUEMAN'S ELEMENTARY BIOLOGY VOL. I For XI Class of 10+2>Chapter 21 - Breathing and Exchange of Gases>TEST QUESTIONS>Q 3

Discuss the transport of gases (O₂and CO₂) in the blood.

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TRUEMAN'S ELEMENTARY BIOLOGY VOL. I For XI Class of 10+2>Chapter 21 - Breathing and Exchange of Gases>TEST QUESTIONS>Q -1

The diagram represents the human larynx. Choose the correct combination of labelling from the options given.

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TRUEMAN'S ELEMENTARY BIOLOGY VOL. I For XI Class of 10+2>Chapter 21 - Breathing and Exchange of Gases>TEST QUESTIONS>Q -2

Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?

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TRUEMAN'S ELEMENTARY BIOLOGY VOL. I For XI Class of 10+2>Chapter 21 - Breathing and Exchange of Gases>TEST QUESTIONS>Q -3

The figure given below shows a small part of the human lung where the exchange of gases takes place. Select the option which represents labelled parts (A, B, C and D) correctly identified along with their function.

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TRUEMAN'S ELEMENTARY BIOLOGY VOL. I For XI Class of 10+2>Chapter 21 - Breathing and Exchange of Gases>TEST QUESTIONS>Q -4

When the blood contains a high percentage of CO₂ and a very low percentage of O₂, the breathing stops and the person becomes unconscious. This condition is known as

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TRUEMAN'S ELEMENTARY BIOLOGY VOL. I For XI Class of 10+2>Chapter 21 - Breathing and Exchange of Gases>TEST QUESTIONS>Q -5

The amount of CO₂ in expired air is about

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TRUEMAN'S ELEMENTARY BIOLOGY VOL. I For XI Class of 10+2>Chapter 21 - Breathing and Exchange of Gases>TEST QUESTIONS>Q -6

Emphysema is a _____.

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