5.3 Diffusion Flashcards
Define diffusion
The net movement of particles from a region of higher concentration to a region of lower concentration (down the concentration gradient)
Is diffusion an active or passive process?
Passive, it does not require metabolic energy.
Where is the energy for diffusion supplied from?
From the kinetic energy of random movement of molecules
When does diffusion stop?
When there is a concentration equilibrium between the two areas.
What is an equilibrium?
A balance, or no difference, in concentrations.
What are the factors affecting the rate of diffusion? (Simple diffusion)
Distance, temperature, concentration difference.
What are the factors affecting the rate of diffusion across membranes?
Distance, temperature, concentration difference, surface area, thickness of membrane, number of protein channels present.
How does distance affect the rate of diffusion?
As distance decreases, the rate of diffusion increases.
Explain how distance affects the rate of diffusion.
-Particles move at high speeds and are constantly colliding, which slows down their overall movement.
-Over short distances, there are less collisions taking place, so the rate of diffusion is higher.
Why are cells microscopic?
So that they can maximise their surface area : volume ratio to increase the rate of diffusion.
How does temperature affect the rate of diffusion?
As temperature increases, the rate of diffusion increases.
Explain how temperature affects the rate of diffusion.
At higher temperatures, the particles have more kinetic energy, and can move at higher speeds, increasing the rate of diffusion.
How does concentration difference affect the rate of diffusion?
The greater the difference in concentration, the greater the rate of diffusion.
Explain how concentration difference affects the rate of diffusion.
The overall movement will be larger if the concentration difference is greater.
What is the definition of simple diffusion?
Diffusion in the absence of a barrier or membrane.
What does diffusion across membranes involve?
Particles passing through the phospholipid bilayer.
When can diffusion across membranes only happen?
When the membrane is permeable to the particles (for example if the particles are non-polar, they can diffuse freely)
How permeable are membranes?
Partially permeable
What makes membranes partially permeable?
-The hydrophobic interior of the membrane repels substances with a charge, so they cannot easily pass through
-Polar molecules can diffuse through membranes at a very slow rate
-Small polar molecules pass through more easily than larger ones.
What is facilitated diffusion?
Diffusion across a membrane through a protein channel
What types of proteins are involved in facilitated diffusion?
Carrier proteins, channel proteins.
Why are membranes with channel proteins selectively permeable?
Because the channel proteins are specific to one molecule or ion.
