Why does the cell sometimes have to expend energy to move individual molecules across the cell membrane?

Normally, molecules move naturally down a concentration gradient [From an area of high concentration to an area of low concentration] by a process called diffusion. However, sometimes the concentration of the needed substance is higher in the cell than out of it, so the cell uses a different process called Active Transport. Unlike Diffusion, Active transport requires energy, as it is going against a concentration gradient.

Cells expend energy to move cells across the cell membrane as they use Active transport rather than diffusion.

starchy vegetables are high in carbohydrates.

starchy vegetables contain more carbohydrates than non-starchy vegetables.

explanation:

there are two primary categories of carbohydrates, essentially differentiated on the basis of their carbohydrate content (which is in the form of starch - a complex carbohydrate):

those vegetables which contain little amounts of starch are termed as non-starchy vegetables, and some examples include: artichokes, broccoli and bean sprouts.

vegetables high in their starch content are distinguished as starchy vegetables, and some examples include: potatoes, chickpeas and corn.