Active transport is only used to move molecules against the concentration gradient. True or False?

Active transport is only used to move molecules against the concentration gradient. True or False?

• A. True
• B. Not always
• C. Always
• D. False

Answer: (D)

Active transport uses energy to move substances uphill, against their gradient, and includes pumps and secondary transport systems that rely on another gradient to drive uptake. But this isn’t the whole story. There are energy-dependent cellular processes, like vesicular transport (endocytosis and exocytosis), that move cargo without a simple, single-mol-level uphill transport across the membrane, and transporter proteins can operate in reverse under different conditions. Because of these cases, active transport isn’t limited to moving substances strictly against a concentration gradient in every scenario. Hence the statement is false.

Active transport uses energy to move substances uphill, against their gradient, and includes pumps and secondary transport systems that rely on another gradient to drive uptake. But this isn’t the whole story. There are energy-dependent cellular processes, like vesicular transport (endocytosis and exocytosis), that move cargo without a simple, single-mol-level uphill transport across the membrane, and transporter proteins can operate in reverse under different conditions. Because of these cases, active transport isn’t limited to moving substances strictly against a concentration gradient in every scenario. Hence the statement is false.