The correct answer is c) Two. When glucose is reabsorbed by the proximal convoluted tubule, it is co-transported with sodium ions. This is known as secondary active transport. As sodium ions are actively transported out of the tubule cells into the interstitial fluid, glucose molecules are able to passively diffuse into the tubule cells along with the sodium ions. This co-transport mechanism allows for efficient reabsorption of glucose from the filtrate back into the bloodstream.
