Question

Diffusion rate is affected by (a) Concentration gradient (b) Membrane permeability through which it occur (c) Pressure and temperature (d) All of these

Short answer

The correct answer is (d) All of these. All these factors - concentration gradient, membrane permeability, pressure and temperature - influence the rate of diffusion.

Step-by-step solution

Evaluate Option A - Concentration Gradient

The concentration gradient affects the diffusion rate. Diffusion occurs as molecules move from a region of higher concentration to a region of lower concentration. The larger the gradient between these two regions, the faster the rate of diffusion.

Evaluate Option B - Membrane Permeability

The permeability of the membrane through which diffusion occurs also affects the diffusion rate. If a membrane is highly permeable to certain particles, these particles will diffuse more rapidly across it than across a membrane that is less permeable.

Evaluate Option C - Pressure and Temperature

Both pressure and temperature influence the rate of diffusion. Higher temperatures or pressures increase the kinetic energy of particles, leading to increased rates of diffusion.

Evaluate Option D - All of the Above

Looking at the three previous steps, it's clear that all these factors (concentration gradient, membrane permeability, pressure and temperature) do have an impact on the diffusion rate. This makes option D the correct answer.

Key concepts

Concentration Gradient

Understanding the concentration gradient is crucial to grasp the movements of particles in various environments, including biological systems. A concentration gradient exists whenever there is a difference in the concentration of a substance across a space. Imagine a crowded room where everyone wants to escape to a less crowded area outside; the movement of people from the inside to the outside represents a high-to-low concentration flow.

This gradient acts as a driving force for diffusion, propelling the particles from a region where they are more concentrated to one where they are less so. This process continues until the concentrations are equal on both sides, a state known as equilibrium.

In biology, cells often maintain concentration gradients across their membranes, which allows for the selective import and export of substances. Essential nutrients flow into the cell where they are less concentrated, while waste products are expelled to areas of lower concentration.

Membrane Permeability

Membrane permeability is a term that refers to the ease with which molecules can pass through a membrane. Biological membranes, such as cell membranes, are selectively permeable; they allow certain molecules to pass while blocking others. This selectivity is crucial for cellular function, as it enables the cell to maintain a distinct internal environment.

Several factors contribute to a membrane's permeability, including the size and polarity of the molecules trying to pass through, as well as the presence of channels or carriers within the membrane that assist in the transport of specific substances. For instance, small nonpolar molecules, like oxygen and carbon dioxide, can easily diffuse through cell membranes, as they are lipophilic or fat-loving. In contrast, larger polar molecules, such as glucose, require specific transport proteins to help them cross efficiently.

When evaluating diffusion rate, a membrane with a higher permeability will allow a faster exchange of substances compared to one with lower permeability. This concept plays a crucial role in processes such as respiration, nutrient absorption, and the excretion of waste products.

Pressure and Temperature

Pressure and temperature stand as two physical factors that deeply influence the rate of diffusion. Just as squeezing a tube of toothpaste increases the pressure and expels the paste more quickly, increasing the pressure in a system can propel molecules to move faster.

Temperature, on the other hand, is directly related to the kinetic energy of particles. Higher temperatures impart more energy to molecules, causing them to move more rapidly. This increased motion results in more collisions and a greater likelihood that particles will spread out or diffuse. For students visualizing this process, think of how sugar dissolves more quickly in hot tea compared to cold water.

The relationship between these factors and diffusion is constantly observed in nature and industry. For instance, in the human body, oxygen distribution is optimized by the lung's warm temperature and the pressure differences in the circulatory system.