In the experiment with Na+ and lycine, what explanation best fits the observed concentrations?

The option that has been selected is based on the observed behavior of sodium ions (Na+) and lysine during the transport process. In this scenario, lysine, an amino acid, is typically transported via a sodium-dependent transport mechanism, where the gradients of both sodium and lysine play essential roles.

When lysine concentration is lower on one side of a membrane, sodium ions can bind to specific transporters located in that area. This binding induces a conformational change in the transporter, allowing lysine to be co-transported along with Na+. The important aspect here is that the movement of sodium occurs from an area of higher concentration to an area of lower concentration, which is energetically favorable. This movement provides the necessary energy for the transport of lysine against its concentration gradient, effectively pulling lysine into the area where its concentration is lower.

Consequently, the correct explanation underscores the role of sodium in facilitating the movement of lysine through a process that does not merely rely on passive diffusion but rather utilizes the established sodium gradient to actively transport lysine into the cell. This is a classic example of secondary active transport, where one solute's gradient (Na+) is used to drive the transport of another (lysine), demonstrating an intricate coupling