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level: 4.2 Diffusion

Questions and Answers List

level questions: 4.2 Diffusion

QuestionAnswer
Diffusion definition- The net movement of molecules from a region of high concentration to a region of low concentration - Until evenly distributed - Passive
Key points of diffusion- No energy needed - Particles diffuse down concentration gradient - Only free particles can diffuse through cell membranes
Simple diffusion meaning- When molecules diffuse directly through a cell membrane
Facilitated diffusion- When large or charged particles diffuse through carrier or channel proteins in the membrane
Carrier proteins- Large molecules attach to carrier proteins - The protein changes shape - This releases molecule on the opposite side of the membrane - Different carrier proteins for different molecules
Channel proteins- Pores in the membrane for charged particles to move through - Different channel proteins for different molecules
Factors that affect the rate of simple diffusion- Concentration gradient - The thickness of exchange surface - The surface area
Concentration gradient and simple diffusion- The higher it is the faster the rate - Difference in concentration decreases as equilibrium is reached
The thickness of exchange surfaces and simple diffusion- The thinner the exchange surface the faster the rate
Surface area and simple diffusion- The larger the surface area the the faster the rate e.g. microvilli
Factors that affect the rate of facilitated diffusion- The concentration gradient - The number of channel or carrier proteins
The concentration gradient and facilitated diffusion- The higher it is the faster the rate - Difference in concentration decreases as equilibrium is reached
The number of channel or carrier proteins and facilitated diffusion- The more proteins the faster the rate - Once all proteins are in use, facilitated diffusion cant happen any faster