Which Molecule, When Moving Across a Plasma Membrane, Would Require

Question

Which molecule, when moving across a plasma membrane, would require the most ATP to be used?
A) a water molecule
B) a simple sugar, such as glucose
C) a dissolved gas, such as carbon dioxide
D) an ion moving against a concentration gradient

Accepted Answer

Ions moving against a concentration gradient require the most ATP to be used as it involves active transport, which requires energy. This is because ions move from an area of low concentration to high concentration which is energetically unfavorable.