Question

1. in terms of diffusion, describe what is most likely to happen to the particles in the image below? (the dashed lines represent a plasma membrane)
2. explain why energy is not required for facilitated diffusion.
3. using the diagram above, label a) simple diffusion, b) facilitated diffusion, and c) osmosis
4. describe the movement of molecules in diffusion.
5. what type of molecules pass directly through the membrane?
6. what type of molecules pass through the membrane via channel proteins?
7. what types of molecules pass through the membrane via carrier proteins?

Explanation:

1. Particles will move from area of higher concentration (bottom) to area of lower concentration (top) across the plasma - membrane due to diffusion.
2. Facilitated diffusion is a passive process that moves molecules down their concentration gradient, so no energy (ATP) is required as it does not work against the gradient.
3. a) Simple diffusion: Molecules passing directly through the lipid - bilayer of the membrane. b) Facilitated diffusion: Molecules passing through channel or carrier proteins. c) Osmosis: Movement of water molecules through aquaporins (a type of channel protein) across the membrane.
4. Molecules in diffusion move randomly from an area of higher concentration to an area of lower concentration until equilibrium is reached.
5. Small, non - polar molecules (e.g., oxygen, carbon dioxide) can pass directly through the membrane.
6. Ions (e.g., sodium, potassium) and some small polar molecules pass through the membrane via channel proteins.
7. Larger polar molecules (e.g., glucose) and some ions pass through the membrane via carrier proteins.

Answer:

1. Particles will diffuse from the more concentrated area (bottom) to the less concentrated area (top) across the plasma membrane.
2. Facilitated diffusion is a passive transport down the concentration gradient, so no energy is needed.
3. a) Simple diffusion: Molecules crossing lipid - bilayer directly. b) Facilitated diffusion: Molecules using channel or carrier proteins. c) Osmosis: Water movement through aquaporins.
4. Molecules move randomly from high to low concentration until equilibrium.
5. Small, non - polar molecules.
6. Ions and some small polar molecules.
7. Larger polar molecules and some ions.