Which of the following determines the direction of gas movement?
a. Solubility in water
b. Partial pressure gradient
c. Temperature
d. Molecular weight and size of the gas molecule

Verified step by step guidance

Understand that gas movement, especially in biological systems like the lungs, occurs primarily by diffusion.

Recall that diffusion of gases depends on differences in partial pressures, which create a gradient that drives gas molecules from areas of higher partial pressure to areas of lower partial pressure.

Recognize that while solubility, temperature, and molecular weight can affect the rate of diffusion, they do not determine the direction of gas movement.

Identify that the key factor determining the direction of gas movement is the partial pressure gradient, because gases move down their partial pressure gradients.

Conclude that among the options given, the partial pressure gradient (option b) is the correct determinant of the direction of gas movement.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Partial Pressure Gradient

The partial pressure gradient refers to the difference in the partial pressures of a gas between two areas. Gas molecules move from regions of higher partial pressure to lower partial pressure, driving diffusion. This gradient is the primary factor determining the direction of gas movement in processes like respiration.

Solubility in Water

Solubility in water describes how well a gas dissolves in a liquid, such as blood or water. While it affects the amount of gas that can be carried or absorbed, it does not determine the direction of gas movement, which depends on pressure differences.

Molecular Weight and Size of Gas Molecules

Molecular weight and size influence the rate at which gas molecules diffuse, with smaller and lighter molecules generally diffusing faster. However, these factors do not dictate the direction of gas movement, which is governed by partial pressure gradients.

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Related Practice

Textbook Question

The detergent-like substance that keeps the alveoli from collapsing between breaths because it reduces the surface tension of the water film in the alveoli is called:

a. Lecithin

b. Bile

c. Surfactant

d. Reluctant

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Textbook Question

Oxygen and carbon dioxide are exchanged in the lungs and through all cell membranes by:

a. Active transport

b. Diffusion

c. Filtration

d. Osmosis

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