Why does sodium and potassium ions need a protein pump to pass through the cell membrane? A. The ions have a charge and cannot pass directly through the cell membrane.
B. The ions are moving against the concentration gradient.
C. Energy is needed to move the ions.
D. All of the above.

Study the picture of the ocean. which is the best example of an organism’s niche shown in the picture? a. the environment contains several of the same species of coral. b. the shallow area of the ocean meets the needs of the coral and the fish. c. the ocean has fish and coral that live in the same area. d. the coral take in food from the water and provide shelter for the fish.

What could happen if two base pairs on a strand of dna or switched

What are the subsystem of the earth