15. Energy is required to transport moleculesa. if they are charged, like chloride ions.b. against the concentration gradient.c. if they are large, like amino acids.d. dissolved gases needed for respiration.e. water when it is needed for photosynthesis.
Active transport is when the molecules are moved across the cell membrane using energy, which happens when the molecule has to go against the concentration gradient, this is, from a lower concentration to a zone with greater concentration (B).
