CBSE Questions for Class 11 Medical Biology Breathing And Exchange Of Gases Quiz 15 - MCQExams.com

Nearly 20-25% of $$CO_{2}$$ is transported by RBCs whereas 70% of it is carried as bicarbonate in plasma. About 7% of $$CO_{2}$$ is carried in a dissolved state through plasma. About 97% of $$O_{2}$$ is carried by RBCs in the blood. About 3% of $$O_{2}$$ Is transported in a dissolved state through the plasma.

The given graph shows the relationship between the partial pressure of oxygen with the amount of oxygen that can bind with haemoglobin. The P$$O_{2}$$ of the air within alveoli is about 100 mm Hg. As the blood travels through the systemic blood capillaries, oxygen leaves the blood and diffuses into the tissues. Consequently, the bipod that leaves the tissues in the veins has a P$$O_{2}$$ that is decreasing (in a resting person) to about 40 mm Hg. Therefore, A depicts oxygenated blood and B depicts systemic blood. The steep portion of the curve from 60 down to 20 mm Hg is ideal for unloading oxygen in the tissue, Le., for a small decrease in P$$O_{2}$$ (due to diffusion of oxygen) a large quantity of oxygen can be unloaded to the peripheral tissue capillary. During strenuous exercise, the muscles accelerated metabolism uses more oxygen from the capillary blood and thus decreases the venous blood P$$O_{2}$$, for example, the P$$O_{2}$$ of the venous blood could drop to 20 mm Hg. Hence, D, E and F show venous blood in exercise, normal venous blood and normal arterial blood respectively. As we know, in the resting person, the P$$O_{2}$$ of tissue is 40 mm Hg, which is favourable for oxygen diffusion from arterial blood to the tissues. Oxygen unloaded to the tissues by arterial blood is 5 mL/100 mL of blood (20 mL- 15 mL = 5mL/100mL, from the graph). During strenuous exercise, the muscle interstitial fluid P$$O_{2}$$ falls to 20 mm Hg, so the oxygen that unloads to the tissue Is 15 mL/100 ml of blood, (20 - 5) ml/100 mL = 15 mL/100mL, from the graph i.e., three times as much as normal.

If alveolar pressure ($$P_{alv}$$) is negative with respect to atmospheric pressure ($$P_{atm}$$), then driving force for airflow is inward i.e., from the atmosphere into the lungs.

• The nasopharynx is the portion of the pharynx. Other two portions of the pharynx are oropharynx and hypopharynx.
  
• The larynx is called as a cartilaginous box as it is made up of 9 cartilages which help in the production of voice.
  
• Primary and secondary bronchi are supported by incomplete hyaline cartilage c-shaped rings.
  
• The pleural fluid of pleural space reduces friction on lung surface. The pleural fluid is secreted by visceral(inside) pleura.
  

• The tidal volume represents the volume of air inhaled or exhaled during normal respiration. The value of tidal volume in a normal healthy person is approximately 6000-8000 ml/min.

Sum of the partial pressure of all gases is 760 mm of Hg.

• There are three pair of conchae are present in our nose on either side of the septum.

Ganong's respiroscope is a device which is used to demonstrate or measure the production of carbon dioxide during aerobic respiration.

During inspiration external intercoastal muscles and diaphragm contract because it allows air to be moved into the lungs and requires the contraction of various musceles; the diaphragm and external intercoastal muscles contract.

Oxygen hemoglobin dissociation curve - This curve shows the relationship between oxygen level and hemoglobin saturation or we can say it shows the affinity for hemoglobin.

Due to low oxygen tension and high carbon dioxide oxyhaemoglobin at the tissue level liberates the oxygen to the cells. Oxygen dissociates from the hemoglobin and diffuses into tissue.

Gaseous exchange occurs when a large surface is provided which increases the quantity and quality of exchange with a moist lining which helps in capturing impure substances and also close to blood capillaries which increases more solubility and transfer of gaseous substances. However, thick walls hinder gaseous exchange. 

Respiratory quotient if the protein is 0.8-0.9

• The part starting with the external nostrils up to the terminal bronchioles constitute the conducting part whereas the alveoli and their ducts form the respiratory or exchange part of the respiratory system.
• The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs.
  
• Within the exchange part, the exchange of gases (O$$_2$$ and CO$$_2$$)  takes place between alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.
  

A.Correct option -A

Insects, and some other invertebrates, exchange oxygen and carbon dioxide between their tissues and the air by a system of air-filled vasculat tubes called tracheae. Tracheae open to the outside through small holes called spiracles. Insects have an impermeable exoskeleton and internal gas exchange system in order to prevent water loss (dessication). This is an adaptation to their terrestrial (land) lifestyle. These tracheae are highly branched helping to increase the Surface area : volume ratio available for gas exchange.

Hint: One of the prominent symptoms of lead poisoning is sluggishness and fatigue. 

Part 1- Poison:
The substance which can result in death or harm organs, tissues due to its action is termed as poison. Poisons depending on its chemical component is classified into two types, they are;

1. Metallic poison

2. Non-metallic poison

Metallic poison are often slowly eliminated and gets accumulated in the body. 

Part 2- Lead poisoning:
Lead [Pb (plumbum)] is a heavy metal. They are the main constituent of paint, industrial dust and effluents and also gasoline products. This metallic poison often on exposure poses a great threat to health. The symptoms of lead poisoning are vomiting, breathlessness, fatigue, abdominal pain, anemia, etc.

Part 3- Action of lead on hemoglobin:
The chronic exposure to lead poses risk to the process of formation of hemoglobin. It inhibits the ability to produce hemoglobin by disrupting the steps in the heme synthesis pathway, which ultimately decreases the hemoglobin content and thereby causing anemia.

Part 4- Conclusion:
Hemoglobin is an oxygen carrier molecule present in red blood cells. Lead poisoning affects the synthesis of hemoglobin, thereby reducing its oxygen carrying capacity.

Final Step: Lead poisoning affects the oxygen carrying capacity of blood cell as it affects the heme-synthesis pathway.