Determine if each statement applies to facilitated diffusion, active transport, or both.
A Does not require energy
B Molecules move against their concentration gradient
C Requires a membrane protein
D Requires energy
E Molecules move down their concentration gradient
The correct answer and explanation is :
Let’s break down each statement and determine whether it applies to facilitated diffusion, active transport, or both.
A. Does not require energy
- Correct answer: Facilitated diffusion
- Explanation: Facilitated diffusion is a passive transport mechanism, meaning it does not require energy. Molecules move across the cell membrane from an area of higher concentration to an area of lower concentration with the help of a transport protein. Since no ATP or energy is needed, this process relies purely on the concentration gradient. Active transport, on the other hand, requires energy to move molecules against their concentration gradient, so it does require energy.
B. Molecules move against their concentration gradient
- Correct answer: Active transport
- Explanation: Active transport is the process where molecules are transported from a region of lower concentration to a region of higher concentration, against their concentration gradient. This requires energy, typically in the form of ATP. Facilitated diffusion does not involve movement against a concentration gradient; it only moves molecules from an area of higher concentration to an area of lower concentration, which is why it does not require energy.
C. Requires a membrane protein
- Correct answer: Both facilitated diffusion and active transport
- Explanation: Both facilitated diffusion and active transport require a membrane protein to assist in the movement of molecules. In facilitated diffusion, the membrane protein acts as a channel or carrier to allow larger or charged molecules (such as glucose or ions) to pass through the membrane. In active transport, membrane proteins, such as pumps, actively transport molecules across the membrane, often using ATP to do so. Therefore, both processes rely on membrane proteins for molecular transport.
D. Requires energy
- Correct answer: Active transport
- Explanation: Active transport is energy-dependent because it involves moving molecules against their concentration gradient, a process that requires ATP or another form of energy. Facilitated diffusion, by contrast, is a passive process that moves molecules down their concentration gradient and does not require energy.
E. Molecules move down their concentration gradient
- Correct answer: Facilitated diffusion
- Explanation: In facilitated diffusion, molecules move from an area of higher concentration to an area of lower concentration, down their concentration gradient. This passive movement requires no energy, as it follows the natural tendency of molecules to disperse. Active transport, in contrast, moves molecules against their concentration gradient, so it does not fit this description.
Conclusion:
- Facilitated diffusion is a passive process that does not require energy, moves molecules down their concentration gradient, and requires a membrane protein.
- Active transport requires energy, moves molecules against their concentration gradient, and also requires a membrane protein.
Understanding these distinctions is crucial for comprehending how cells maintain homeostasis by regulating the movement of various substances.