Diffusion

Definition

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached. This process plays a crucial role in various biological systems, particularly in how substances like gases and nutrients move across cell membranes, and it is significantly influenced by the properties of water, which is a key solvent in biological reactions.

5 Must Know Facts For Your Next Test

1. Diffusion is a passive process, meaning it does not require energy input to occur as substances move down their concentration gradient.
2. Factors such as temperature, size of molecules, and the medium through which diffusion occurs can affect the rate of diffusion.
3. In biological contexts, diffusion is essential for processes like respiration, where oxygen diffuses into cells and carbon dioxide diffuses out.
4. Water’s unique properties, including its polarity and ability to form hydrogen bonds, influence how solutes diffuse in biological systems.
5. Cell membranes are selectively permeable, allowing certain substances to diffuse while restricting others, which is critical for maintaining homeostasis.

Review Questions

• How does diffusion contribute to the maintenance of homeostasis in living organisms?
  • Diffusion plays a vital role in maintaining homeostasis by allowing essential substances such as nutrients and gases to move across cell membranes. For example, oxygen diffuses into cells where it is used for cellular respiration, while carbon dioxide produced as a waste product diffuses out. This continuous exchange ensures that cells have the necessary resources for metabolism while removing waste products efficiently.
• Discuss the role of water in facilitating diffusion and how this relates to biological significance.
  • Water serves as a solvent in biological systems and greatly influences the process of diffusion. Its unique properties allow it to dissolve various solutes, creating an environment where diffusion can occur efficiently. For instance, nutrients dissolve in water and then diffuse into cells through the plasma membrane. Additionally, osmosis, a specific type of diffusion related to water movement, is critical for maintaining cell turgor pressure and overall cellular function.
• Evaluate how changes in temperature affect the rate of diffusion and what implications this has for cellular functions.
  • Changes in temperature can significantly impact the rate of diffusion; generally, higher temperatures increase kinetic energy, leading to faster movement of particles. This means that at elevated temperatures, substances can diffuse more quickly across membranes. In a biological context, this has implications for metabolic processes. For instance, higher temperatures can enhance nutrient uptake and waste removal but may also lead to cellular stress if temperatures exceed optimal levels, affecting enzyme activity and overall cellular integrity.

Related terms

Osmosis:

The diffusion of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Concentration Gradient: The difference in the concentration of a substance between two areas, which drives the movement of particles during diffusion.

Passive Transport: The movement of substances across a cell membrane without the use of energy, often involving diffusion or osmosis.