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The diagram represents the movement of sugar molecules across a plasma membrane.Which of the following arguments BEST explains the movement of the sugar molecules?

Question 9 options:

The sugar molecules moved across the membrane through simple diffusion due to the higher concentration of molecules inside the cell and a lesser concentration of molecules outside the cell.

The sugar molecules moved across the membrane through osmosis due to the higher concentration of water molecules outside the cell and the lesser concentration of water molecules inside the cell.

The sugar molecules moved across the membrane through active transport due to the higher concentration of molecules on the outside of the cell and a lesser concentration inside the cell.

The sugar molecules moved across the membrane through facilitated diffusion due to the higher concentration of molecules outside the cell and the lesser concentration of molecules inside the cell.

1 answer

To determine the best explanation for the movement of sugar molecules across a plasma membrane, let's briefly analyze the options provided:

  1. Simple diffusion - This mechanism typically applies to small, nonpolar molecules passing through the membrane without assistance. For sugar molecules, which are polar and larger, simple diffusion is unlikely to be the correct explanation.

  2. Osmosis - This term specifically refers to the movement of water molecules across a semipermeable membrane, not the movement of sugar molecules. Therefore, osmosis is not applicable here.

  3. Active transport - Active transport requires energy (usually from ATP) to move molecules against their concentration gradient. This would suggest that sugar molecules are being moved from an area of lower concentration inside the cell to an area of higher concentration outside, which may not be the typical scenario for sugar movement.

  4. Facilitated diffusion - This process involves the movement of molecules across the plasma membrane via specific transport proteins, typically down their concentration gradient (from higher to lower concentration). If sugar molecules are moving from a higher concentration outside the cell to a lower concentration inside, this would align with facilitated diffusion.

Given these considerations, the best explanation among the provided options is:

The sugar molecules moved across the membrane through facilitated diffusion due to the higher concentration of molecules outside the cell and the lesser concentration of molecules inside the cell.