Question

1. when the cell needs to move molecules from an area of low concentration to one of high concentration, it uses specialized channels or carriers in the cell membrane. this process expends energy and is called

a. active transport.
b. replication.
c. mitosis.
d. passive transport.

Explanation:

To solve this, we analyze each option:

• Option a: Active transport is the movement of molecules against their concentration gradient (from low to high concentration) and requires energy (ATP) and specialized carriers/channels. This matches the description.
• Option b: Replication is the process of copying DNA, not related to molecule movement across cell membranes.
• Option c: Mitosis is cell division, not related to molecule transport.
• Option d: Passive transport moves molecules from high to low concentration (down the gradient) and does not require energy, which is the opposite of the described process.

Answer:

a. Active transport.