Problem 42 - Objective Biology for NEET

Question

Gaseous exchange between blood and alveolar air across respiratory membrane occurs by (a) Osmosis (b) Diffusion (c) Active transport (d) Phagocytosis

Step-by-Step Solution

Answer

The gaseous exchange between blood and alveolar air across the respiratory membrane occurs through diffusion.

Step 1: Understanding the Concepts

Gaseous exchange refers to the transfer of oxygen from the alveolar air to the blood, and the removal of carbon dioxide from the blood to the alveolar air. There are different biological processes that facilitate the transfer of substances, these include osmosis, diffusion, active transport, and phagocytosis.

Step 2: Examining each process

Osmosis refers to the movement of a solvent from a region of low solute concentration to a region of high solute concentration. Active transport uses energy to move substances against a concentration gradient. Phagocytosis is a process that allows a cell to engulf other substances or cells. Diffusion, however, refers to the movement of substances from a region of high concentration to a region of low concentration.

Step 3: Applying the correct concept

In the case of gaseous exchange in the lungs, Oxygen moves from a region of high concentration (in the alveolar air) to a region of low concentration (in the blood). The same can be said for the carbon dioxide, which moves from a region of high concentration (in the blood) to a region of low concentration (in the alveolar air). The process that best describes this scenario is diffusion.

Key Concepts

Gas Exchange

Gas exchange is a critical function of the respiratory system where oxygen is passed from the environment into the bloodstream, and carbon dioxide is expelled from the blood into the environment. This exchange is crucial for maintaining the proper levels of gases in the body and occurs in the tiny sacs within the lungs known as alveoli.

In the alveoli, oxygen from the inhaled air diffuses into the blood in the surrounding capillaries. Simultaneously, carbon dioxide from the blood diffuses into the alveoli to be exhaled. This two-way exchange ensures that the body maintains adequate oxygen levels while eliminating carbon dioxide, a waste product of cellular respiration. Efficient gas exchange is vital for sustaining life and supporting cellular activities. It is facilitated by the thin walls of the alveoli and the close proximity of blood vessels.

Diffusion

Diffusion is the primary mechanism by which gases are exchanged in the lungs. It is a passive process that does not require energy but is reliant on the concentration gradients of the gases.

The principle of diffusion involves the movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is achieved. In the context of the respiratory system, oxygen in the alveolar air, where it is in higher concentration, diffuses into the blood. Conversely, carbon dioxide, which is in higher concentration in the blood, diffuses into the alveolar air.

• Passive Process: No energy is needed for diffusion.
• Concentration Gradient: Drives the movement of gases.
• Equilibrium: Achieved when gas concentrations are balanced.

This straightforward mechanism is essential in ensuring the efficient functionality of the respiratory system.

Alveolar Air

Alveolar air forms a critical component of the gas exchange process. It comprises the air found within the alveoli, the tiny air sacs in the lungs where diffusion occurs. The composition of alveolar air is vital as it directly affects the efficiency of gas exchange.

Alveoli have a large surface area and come into close contact with the capillary network, facilitating rapid gas exchange. The oxygen-rich air that enters the lungs during inhalation fills the alveoli, ready for diffusion into the blood. During this process, the carbon dioxide from the venous blood is exchanged for oxygen, effectively clearing the blood of carbon dioxide and enriching it with oxygen. This exchange through the walls of alveoli ensures that the bloodstream carries adequate oxygen to the body while removing carbon dioxide efficiently.

Respiration

Respiration is a broader term that encompasses the processes of breathing, gas exchange, and cellular respiration. While breathing involves the physical movement of air into and out of the lungs, gas exchange, as previously detailed, occurs at the alveolar level.

Breathing is an involuntary action controlled by the respiratory center in the brainstem, responding to the body's needs based on carbon dioxide and oxygen levels in the blood. Cellular respiration, on the other hand, refers to the metabolic process in which cells use oxygen to produce energy from glucose, producing carbon dioxide as a byproduct.

• Breathing: Involuntary action to move air in and out.
• Gas Exchange: Happens in alveoli, involves diffusion of gases.
• Cellular Respiration: Uses oxygen for energy production.

Each aspect of respiration is interconnected, ensuring that our bodies function efficiently and continuously.