Question

q7. to move to the roots of a plant, a sugar molecule must exit the cell where it was produced and enter the stream of plant fluid that carries sugar to other parts of the plant (known as phloem). a newly created sugar molecule is transported to the phloem through diffusion. this means that sugar molecules:
move randomly within the cell until, by chance, they exit the cell and enter the phloem.
travel away from the cell organelle where they are produced (chloroplast), until they enter the phloem.
travel away from areas of high sugar concentration, such as the chloroplast, until they enter the phloem.
move randomly until they encounter the phloem, and then stop moving as they are carried along by the phloem.

Explanation:

Diffusion is the movement of particles from an area of high concentration to an area of low concentration. Sugar molecules are produced in the chloroplast (high concentration), so they travel away from high - concentration areas (chloroplast) to low - concentration areas (phloem).

• Option 1: Diffusion is not just random movement until chance exit; it's driven by concentration gradients, so this is wrong.
• Option 2: The direction is due to concentration, not just moving away from the chloroplast organelle, so this is incorrect.
• Option 3: Correctly describes diffusion - moving from high (chloroplast) to low (phloem) concentration.
• Option 4: Molecules don't stop moving in phloem; they are still in motion (even if carried, they have random motion too), so this is wrong.

Answer:

C. Travel away from areas of high sugar concentration, such as the chloroplast, until they enter the phloem.