In co-transport and counter-transport, which solute moves downhill: A. potassium B. hydrogen C. sodium D. calcium?

Understand the Problem

The question is asking which solute is involved in the downhill movement in co-transport and counter-transport mechanisms in biological systems. It presents four options: potassium, hydrogen, sodium, and calcium.

More Information

Sodium ions often move down their concentration gradient during secondary active transport, providing the energy needed to transport other substances against their gradients in processes like co-transport or counter-transport.

Tips

A common mistake is confusing which ion moves down the gradient. Remember, sodium typically moves down its gradient in these mechanisms, powering the uphill transport of other substances.

Sources

• Lecture-2 Cell membrane .pdf - KSUMSC - ksumsc.com
• Active transport: primary & secondary overview (article) - Khan Academy - khanacademy.org