selectivity in membrane permeability Flashcards
What does a semi-permeable membrane do?
A semi-permeable membrane allows the passage of certain small solutes and is freely permeable to the solvent (e.g., water).
How is the selective permeability of cell membranes different from that of artificial membranes like Visking tubing?
Cell membranes are more selectively permeable compared to artificial membranes. They control the passage of specific particles more strictly and have variable permeability to substances like water.
What is a selectively permeable membrane?
A selectively permeable membrane allows the passage of certain particles but blocks others, often based on factors like size, polarity, or the presence of specific channels or pumps.
How do facilitated diffusion and active transport contribute to selective permeability?
Facilitated diffusion and active transport contribute to selective permeability because they involve channel proteins and pump proteins that are specific to certain types of particles, allowing only particular molecules to pass through.
How does simple diffusion differ in terms of selectivity?
Simple diffusion is not selective; it depends only on the size and polarity of particles. Small hydrophobic molecules can cross freely, while larger or polar molecules might struggle.
What does the term “partially permeable” mean for cell membranes?
Partially permeable refers to the fact that cell membranes are semi-permeable (allowing some substances to pass) and selectively permeable (controlling the passage of others) depending on the mechanisms in place (e.g., channels, pumps).
