Question

model 3 - facilitated diffusion

1. which part of the cell membrane is shown in more detail in model 3?
2. what is the gap between the proteins called?
3. what type of molecules attach to the protein?
4. explain in detail what happened that allowed the glucose molecules to pass through.

Explanation:

• For question 18: Model 3 shows facilitated diffusion, which involves membrane proteins (channel or carrier proteins). The cell membrane part in detail is the membrane - spanning proteins (like the gated channel).
• For question 19: In the context of membrane proteins, the gap between them (when they form a channel) is the channel pore (in the case of channel - type proteins for facilitated diffusion).
• For question 20: Hormones (as shown in the model) attach to the protein (at the hormone - binding site).
• For question 21: Hormones bind to the protein (at the hormone - binding site). This binding causes a conformational change in the protein (the channel begins to open). As the channel opens fully, it creates a pathway (the gap or pore) through which glucose molecules (which are polar and cannot easily pass through the lipid bilayer) can move down their concentration gradient (from an area of higher glucose concentration to an area of lower glucose concentration) via facilitated diffusion.

Answer:

1. Membrane - spanning proteins (channel proteins).
2. Channel pore.
3. Hormones.
4. Hormones bind to the protein (at the hormone - binding site), causing a conformational change. This change opens the channel (the gap between the proteins), creating a pathway. Glucose molecules, which cannot pass through the lipid bilayer easily (due to being polar), move through the opened channel down their concentration gradient via facilitated diffusion.