Question

1.3.1 test (cst): cell biology unit test
one way that cells maintain homeostasis is by transporting molecules across the cell membrane when a concentration gradient builds up on either side of the membrane. there are several methods of cell transport. passive transport moves small, mostly lipid - soluble molecules, while active transport moves larger proteins and charged ions. the graph below shows the energy needed for cell transport as the concentration gradient increases. which description correctly describes the cell transport indicated by the graph?
a. diffusion of small molecules requiring an initial input of energy
b. active transport of larger molecules requiring the input of energy
c. passive transport of small molecules that generate energy

Explanation:

Active transport requires energy (usually in the form of ATP). As the concentration gradient (which represents the difference in molecule concentration across the membrane) increases, more energy is needed for active transport to move molecules against their concentration gradient (from low to high concentration). Passive transport (like diffusion) does not require energy input as molecules move down their concentration gradient (from high to low concentration). Option A is incorrect because diffusion (a passive - transport process) does not require an initial energy input. Option C is incorrect because passive transport does not generate energy in the context of moving molecules across the membrane; it is a process that occurs spontaneously without energy input for molecule movement.

Answer:

B. Active transport of larger molecules requiring the input of energy