DiffusionCambridge IGCSE Biology: Flashcards

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Define diffusion.

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Define diffusion.: Diffusion is the net movement of particles (molecules or ions) from a region of higher concentration to a region of lower concentration down a concentration gradient, due to the random movement of particles.
What is the source of energy for diffusion?: The kinetic energy of the random movement of molecules and ions provides the energy for diffusion. No additional cellular energy (ATP) is required.
What is meant by a concentration gradient?: A concentration gradient is the difference in concentration of a substance between two regions. Diffusion occurs down the concentration gradient, from high to low concentration.
Name four factors that influence the rate of diffusion.: The four factors are: surface area, temperature, concentration gradient, and distance (or thickness of the barrier).
Explain how surface area affects the rate of diffusion.: A larger surface area allows more particles to diffuse across the barrier per unit time, increasing the rate of diffusion.
Explain how temperature affects the rate of diffusion.: Higher temperature increases the kinetic energy and random movement of particles, causing them to move faster and more frequently, increasing the rate of diffusion.
Explain how concentration gradient affects the rate of diffusion.: A steeper concentration gradient (greater difference in concentration between regions) results in more particles moving down the gradient, increasing the rate of diffusion.
Explain how distance affects the rate of diffusion.: A shorter distance between high and low concentration regions increases the rate of diffusion, as particles take less time to travel across the barrier.
Name two substances that diffuse into cells across the cell membrane.: Oxygen and glucose (or other solutes such as amino acids, ions, or carbon dioxide) diffuse into cells by diffusion.
Name two substances that diffuse out of cells across the cell membrane.: Carbon dioxide and urea (or other metabolic waste products) diffuse out of cells by diffusion.
Explain the importance of gas diffusion in living organisms.: Gas diffusion allows oxygen to enter cells for aerobic respiration and allows carbon dioxide produced by respiration to exit cells, maintaining the concentration gradients necessary for life processes.
Explain the importance of solute diffusion in living organisms.: Solute diffusion allows essential nutrients and ions to enter cells and allows metabolic waste products to exit cells, enabling nutrient uptake, waste removal, and maintenance of cell function.
Is diffusion an active or passive process? Justify your answer.: Diffusion is a passive process because it does not require energy from the cell (ATP). It relies only on the kinetic energy of random particle movement.
Explain why diffusion requires random movement of particles.: Random movement allows particles to move in all directions throughout the medium. Over time, more particles randomly move from the high concentration region to the low concentration region, resulting in net movement down the gradient.
Why is diffusion important for gas exchange in living organisms?: Diffusion enables the exchange of respiratory gases (oxygen and carbon dioxide) between cells and their environment without requiring metabolic energy, allowing cells to obtain oxygen for respiration and remove carbon dioxide waste continuously.