Assume that the import of a particular amino acid across the plasma membrane is observed (1) to occur only down its concentration gradient and (2) to slow when a different but similar amino acid is added to the extracellular fluid. The movement of the amino acid through the membrane is most likely by:

1. the energy lost to disorder metabolism     -entropy

2. related to or possessing motion potential     -kinetic

3. all of the chemical reactions in an organism required for maintenance of the processes of life entropy     -metabolism

4. possible; ability to go into action or perform work kinetic     -potential

5. the study of energy and its transformations thermodynamics     -thermodynamics

b is the correct answer