Many solutes that must move into and out of cells exist in either a protonated o

Question

Many solutes that must move into and out of cells exist in either a protonated or ionized form, or they have functional groups that can be either protonated or ionized. Simple molecules such as CO_2, H_3 PO_4 (phosphoric acid), and NH_3 (ammonia) are in this category, as are organic molecules with carboxylic acid groups, phosphate groups, and/or amino groups. For a cell that must take up ammonia from its environment, will uptake of the charged form require more or less energy than uptake of the uncharged form, assuming that the cell has a negative membrane potential? Explain your answer. Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

Explanation / Answer

To say that the cell has a negative membrane potential means that the inner surface of plasma membrane has a more negative charge than the outer surface. A positively charged sulute such as NH4+ will therefore be drawn inward by the membrane potential, which means that uptake of negatively charged across the plasma membrane will require more energy than the uptake of NH3 assuming the same concentration gradient for the two solutes of course.

Asthere is more negative charge inside the more positive NH4+ will be attracted and neutral such as NH3 will requre less energy for transport than negatively charged molecules due to repulsion of same charges.

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