Gaseous Exchange

 Gaseous Exchange - Short Questions Answers Biology - XI

Chapter # 13 Short Questions Answers

Section IV - Functional Biology

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BOTANY PART

Q.1: Describe Photorespiration in Plants?

Ans: Photorespiration in Plants:

• When plants use oxygen and release CO₂ during day time, in the presence of sunlight, it is called photorespiration.
• Photorespiration occurs in special plants during hot and dry days, such plants are called C₃ plants, for example wheat, rice, sugarcane.

When the weather is hot and dry during the day, the stomata are closed to prevent the loss of water. Photosynthesis takes place, in which O₂ is released. Due to the increase of O₂ than the amount of CO₂, the oxygen combines with an enzyme, called ribulose bisphosphate carboxylase/oxygenase or Rubisco. This enzyme takes part to catalyze the process of carbon dioxide fixation, ribulose bisphosphate combines oxygen instead of CO₂. By the combination of O₂, RuBP compound divides into two compounds.

• Phosphoglyceric acid (PGA)
• Phosphoglycolate

Phosphoglycolate compound forms Serine and CO₂. The process can be shown in the following way.

• Ribulose bisphosphate (RuBP) → PGA + phosphoglycolate
• Phosphoglycolate → Serine + CO₂

By the process it is indicated that photorespiration is similar to respiration, because in this process O₂ is used and CO₂ is released, it is an oxidation process. In photorespiration energy rich compounds ATP are not formed, in this way energy is not produced, so this process is not useful for plants, it is wasteful and without any benefit. It also reduces photosynthesis as a result of which crop production may be reduced.

Q.2: Describe the respiratory system of Cockroach?

Ans: Respiratory Organs of Cockroach:

In cockroach respiratory organs are tube like structures, called trachea. They are present throughout its body in the form of a network. In this way the oxygen is supplied to all.

Continuation of Cockroach Respiration:

The tracheae open to the outside through ten pairs of spiracles (two in the thorax and eight in the abdomen). Valves in spiracles allow abdominal spiracles to open inward for air intake, while thoracic spiracles open outward to release CO₂.

The tracheae branch into smaller tubes, called tracheoles, that penetrate body tissues. The cockroach’s abdomen contracts and expands, facilitating airflow. During expansion, abdominal spiracles open, letting air rush in, filling tracheae and tracheoles. Oxygen diffuses slowly, while CO₂ mixes with air. During contraction, air is expelled through thoracic spiracles.

Q.3: Describe the respiratory system of Fish?

Ans: Respiratory System of Fish:

In fish, the respiratory organs are called gills. These gills arise from the pharynx and open to the outside by gill slits. The water enters through the mouth, passes over the gills, and is then excreted out through gill slits.

Structure of Gills: Each gill consists of rows of numerous structures called filaments, which are arranged in a V-shaped manner. These are supported by a curved bone, called gill bar or gill arch. Each filament contains many plate-like structures known as lamellae. These lamellae contain a network of blood capillaries to absorb oxygen from water.

Mechanism of Respiration: In fish, the blood which is supplied from the heart to the gills is deoxygenated. Gill lamellae allow blood to flow in a direction opposite to the flow of water; this is called counter-current flow. In fish, the water enters through the mouth. This oxygenated water passes over the gills. The blood which enters the gills from the body has a low concentration of O₂ and a high concentration of CO₂. The oxygen of water diffuses into the blood, and CO₂ moves from blood into the water. This exchange is helped by counter-current flow because blood and water move in opposite directions. The water with CO₂ leaves out through the gill slits on the sides of the pharynx.

This counter-current flow is very useful in fishes, allowing them to obtain 80% - 90% of the oxygen from the water flowing over the gills.

Q.4: Describe the respiratory system of Frog?

Ans: Respiratory Organs of Frog:

Frogs are amphibians and have three types of respiration:

• Cutaneous respiration - through the skin.
• Bucco-pharyngeal respiration - through the buccal cavity.
• Pulmonary respiration - through the lungs.

Cutaneous Respiration: Occurs through the skin when the frog is in water or during hibernation.

Bucco-Pharyngeal Respiration: Occurs in the buccal cavity, which has blood capillaries to facilitate gas exchange.

Pulmonary Respiration: Occurs through the lungs, involving:

• External nares (nostrils)
• Internal nares (nostrils)
• Buccal cavity (bucco-pharyngeal part)

Continuation of Frog Respiration:

• Pharynx (bucco-pharyngeal part)
• Larynx (or laryngo-tracheal chamber)
• Bronchi
• Lungs

The nostrils open into the buccal cavity, which has an opening called the glottis leading to the larynx (sound box). The larynx splits into bronchi that open into simple, elastic, spongy sac-like lungs divided into alveoli with capillaries for gas exchange.

Mechanism of Respiration:

1. Inspiration:

   • Air enters through nostrils; the bucco-pharyngeal floor lowers, closing the mouth and glottis.
   • When nostrils close and glottis opens, the floor rises, pushing air into the lungs.
   • Incomplete ventilation occurs as the lungs are not fully emptied or refilled.

2. Expiration:

   • Gas exchange occurs in the alveoli.
   • After exchange, the bucco-pharyngeal floor lowers, transferring air from lungs to the buccal cavity.
   • When the floor moves up, air exits through the nostrils.

Q.5: Describe the respiratory system of Birds.

Ans: Respiratory System of Birds: Respiration occurs through the lungs in birds, known as pulmonary respiration. Respiratory organs include nostrils, nasal passage, larynx, trachea, syrinx (voice box), bronchi, and lungs.

Respiratory System of Birds:

• External Nostrils: Small openings where fresh air enters the nasal cavity, leading to the pharynx.
• Pharynx: Contains a small opening called the glottis, which allows air to pass into the larynx, then into the trachea.
• Syrinx: Located where the bronchi split; produces sound in birds (larynx does not produce sound in birds).
• Lungs & Air Sacs:
  • Birds have compact, reddish, spongy lungs with 8-9 thin-walled air sacs located in the abdomen, neck, and wings.
  • Bronchi pass through the lungs, forming secondary bronchi and parabronchi, which connect to air sacs for constant ventilation.
  • Air sacs work like bellows, pushing air through parabronchi in one direction for efficient oxygen exchange.

Mechanism of Respiration:

• Inspiration: Air enters nasal cavity, moves through glottis, trachea, bronchi, secondary bronchi, and air capillaries for gas exchange, with air stored in air sacs.
• Expiration: Compression of air sacs pushes air through bronchi and out through nostrils. Birds take two breaths per respiration cycle, supporting efficient oxygen supply for high-altitude flight.

Q.6: What are the different organs of respiration in humans?

Ans: Organs of Respiration:

• External Nostrils
• Nasal Cavities
• Internal Nostrils
• Pharynx
• Larynx
• Trachea
• Bronchi
• Lungs

Description:

• External Nostrils & Nasal Cavities: Openings that lead to nasal cavities, which keep air moist and warm before it enters the pharynx.
• Pharynx: Contains the glottis, leading to the larynx. The epiglottis prevents food from entering the glottis.
• Larynx: Known as the voice box, containing vocal cords that produce sound.
• Trachea: A windpipe with ring-like structures to prevent collapse, allowing easy airflow.
• Bronchi & Bronchioles:
  • The trachea splits into bronchi that enter each lung, further branching into smaller bronchi and bronchioles.
  • Bronchioles end in alveoli, small sacs rich in blood capillaries for gas exchange.

Alveoli: Considered the main site for gas exchange, with a thin fluid layer aiding oxygen absorption by the blood.

Lungs: The lungs are two pink, spongy organs located in the thoracic cavity, surrounded by ribs and intercostal muscles. Each lung is encased in a thin membrane called pleura, and the space they occupy is known as the pleural cavity. The diaphragm, a thin muscular wall, separates the thorax from the abdomen. Lungs expand and contract through systematic diaphragm movements and rib adjustments driven by intercostal muscles.

Q.7: Describe the mechanism of breathing?

Ans: Mechanism of Breathing: Breathing involves two main steps:

• Inspiration (Inhalation)
• Expiration (Exhalation)

During breathing, air is taken in due to negative pressure in the thoracic cavity, where pressure is lower than atmospheric pressure (negative pressure breathing).

Inspiration (Inhalation):

• The diaphragm moves downward, and intercostal muscles push ribs forward, enlarging the pleural cavity.
• This expansion allows air to flow through the nasal cavity, pharynx, larynx, trachea, and bronchi into the alveoli of the lungs.
• Oxygen diffuses into the blood in alveolar capillaries, where it binds with hemoglobin, while CO₂ diffuses into the air.

Expiration (Exhalation):

• After gas exchange, the diaphragm rises, and ribs move inward due to intercostal muscle relaxation.
• This reduces thoracic cavity volume, compressing the lungs and forcing air out through the bronchi, trachea, and nasal cavity.

Q.8: Write a note on rate of breathing in man?

Ans: Rate of Breathing: Humans have two types of breathing:

• Voluntary Control Breathing: Involves conscious control, allowing brief breath-holding or adjusted breathing as needed.
• Involuntary Control Breathing: Automatic and managed by respiratory and cardiovascular coordination. CO₂ and H⁺ levels in blood influence breathing rate, detected by chemoreceptors (aortic and carotid bodies). The medulla oblongata in the brain regulates breathing rate based on these concentrations.

Q.9: Describe the different disorders of respiration in man?

Ans: Disorders of Respiratory Tract: Some common respiratory disorders include:

• Lung Cancer: Caused primarily by smoking; substances like nicotine and SO₂ damage respiratory tract cells, removing cilia, allowing dust and germs to enter. Abnormal cell growth damages the lung lining.

Respiratory Disorders (continued):

• Emphysema:

  • A disorder where alveoli are damaged and lose elasticity, often due to pollutants like nitrogen oxide (NO) and sulfur dioxide (SO₂).
  • Damaged alveoli reduce oxygen supply to body parts, causing breathing difficulties, lethargy, and irritability.
  • Precaution & Control:
    • Maintain a pollution-free environment.
    • Use effective medications.

• Asthma:

  • A respiratory disease marked by recurrent difficulty in breathing, often triggered by allergens like dust, pollen, or animal fur.
  • Asthma can lead to bronchiole contraction, posing risks to patients.
  • Precaution & Treatment:
    • Use effective medication and ensure a pollution-free environment.

• Tuberculosis:

• A serious lung disease caused by Mycobacterium tuberculosis, with symptoms like persistent cough, chest pain, and fever.
• It is contagious and spreads through respiratory droplets.
• Precaution & Treatment:
• Isolate patients, avoid sharing personal items, and use antibiotics.

Q.10: Write a note on Lung capacities?

Ans: Lung Capacities:

• Tidal Volume: Approximately 500 ml of air taken in and out during normal breathing (10% of lung capacity).
• Vital Capacity: Maximum air volume during deep breaths, around 4 liters.
• Residual Volume: Remaining air in the lungs after exhalation, ensuring they do not collapse.

Q.11: Describe the role of Hemoglobin (Transport of O₂)

Ans: Role of Hemoglobin:

• Hemoglobin is a red, iron-containing protein in red blood cells (RBCs) that binds with oxygen.
• Each hemoglobin molecule can carry four oxygen molecules, with each RBC containing millions of hemoglobin molecules.
• Oxygen binds to hemoglobin to form oxyhemoglobin, which transports oxygen throughout the body and releases it to tissues.

Q.12: Describe the transport of CO₂ in the body of man?

Ans: Transport of CO₂:

• CO₂ is transported from tissues to the lungs by:
• Hemoglobin: Carries approximately 35% of CO₂.
• Plasma: Dissolves CO₂ in water of plasma for transport.

Transport of CO₂ (continued):

• Carbaminohemoglobin Formation: CO₂ combines with hemoglobin to form carbaminohemoglobin, which breaks down in alveoli, releasing CO₂.
• Water of RBCs: 60% of CO₂ is transported in the water of RBCs through reactions that form compounds like carbonic acid and bicarbonate.
  • Reactions include:
    • $\text{CO₂ + H₂O} \leftrightarrow \text{H₂CO₃ (Carbonic acid)}$
    • $\text{H₂CO₃} \leftrightarrow \text{H⁺ + HCO₃⁻ (Bicarbonate)}$
    • $\text{H⁺ + NH₃} \leftrightarrow \text{NH₄⁺ (Ammonium)}$
• Water of Plasma: 5% of CO₂ is transported in plasma as potassium bicarbonate.
  • Reactions include:
    • $\text{CO₂ + H₂O} \leftrightarrow \text{H₂CO₃}$
    • $\text{H₂CO₃} \leftrightarrow \text{H⁺ + HCO₃⁻}$

Q.13: What is the role of Myoglobin?

• Role of Myoglobin: Myoglobin, smaller than hemoglobin, also absorbs oxygen and provides red color to muscles due to its strong oxygen-binding ability.

Q.14: Differentiate between Positive Pressure Breathing & Negative Pressure Breathing:

• Positive Pressure Breathing: Involves more body pressure relative to atmospheric pressure, occurring during expiration, where CO₂ is expelled.
• Negative Pressure Breathing: Involves less pressure in the thoracic cavity compared to atmospheric pressure, occurring during inspiration, where oxygen is inhaled.

Inspiration and Expiration (Comparison):

Inspiration	Expiration
Oxygen is taken in, fresh air enters.	CO₂ is expelled, air is not fresh.
Decreased thoracic cavity pressure.	Increased thoracic cavity pressure.
Ribs move outward, enlarging thoracic cavity.	Ribs move inward, reducing thoracic cavity.
Energy-consuming process.	Not an energy-consuming process.