How does active transport differ from passive
transport?
1. Molecules move down a concentration
gradient in active transport.
2. Carrier proteins are used only in active
transport.
3. Energy is required only in active trans-
port.
4. Energy is required only in passive trans-
port.
Active transport differs from passive transport in several ways:
1. Molecules move against the concentration gradient in active transport, while they move down the concentration gradient in passive transport. In active transport, molecules are pumped from an area of lower concentration to an area of higher concentration, requiring energy to overcome this uphill movement. In contrast, passive transport allows molecules to simply diffuse or flow down their concentration gradient without the need for energy.
2. Carrier proteins are used in both active and passive transport, but they play a more prominent role in active transport. Carrier proteins are membrane proteins that aid in the movement of molecules across cell membranes. In active transport, these carrier proteins undergo conformational changes to actively transport molecules against their concentration gradient. In passive transport, carrier proteins may still be involved, but their role is primarily to facilitate the movement of molecules with the concentration gradient.
3. Energy is required only in active transport. Active transport mechanisms, such as the sodium-potassium pump, require the input of energy (usually in the form of ATP) to move molecules against their concentration gradient. This energy is used to change the conformation of the carrier proteins and drive the movement of molecules. In passive transport, no energy is required as molecules move freely down their concentration gradient.
4. The statement "Energy is required only in passive transport" is incorrect. Passive transport does not require energy as molecules move spontaneously down their concentration gradient. However, active transport does require energy. Therefore, option 4 is incorrect.