Question

What does active transport of K+ in the Malpighian tubules ensure?

a) Maintenance of a high concentration of K+ in the tubules.
b) Removal of excess K+ from the tubules.
c) Secretion of K+ into the surrounding tissues.
d) Reabsorption of K+ from the surrounding tissues.

Answer 1

The active transport of K+ in the Malpighian tubules maintains a high concentration of potassium ions, ensuring the efficient excretion of waste and conservation of water, while maintaining osmotic balance.

Step-by-step explanation:

Active transport of K+ (potassium ions) in the Malpighian tubules ensures the maintenance of a high concentration of K+ within the tubules. When Na+ and/or K+ ions are actively transported into the lumen of the tubules, water follows osmotically, forming urine. As the urine passes through the insect's intestine and into the rectum, nutrients diffuse back into the hemolymph while the ions are actively transported back in, and water again follows. The concentrated waste is then excreted, all while maintaining osmotic balance in the organism.

The correct answer to the given question is a) Maintenance of a high concentration of K+ in the tubules. This process is essential for the excretion of wastes while conserving water and ensuring solute balance, which is particularly critical for insects and other arthropods living in dry environments.