Question

In 1968, Harold Reuter and Norbert Seitz published findings that, when sodium ions are removed from the medium surrounding a cell, the flow of calcium ions is inhibited. They proposed that there might be a mechanism for exchanging the two ions. What does this experiment suggest about the transport of ions in and out of cells?

a) It happens passively through diffusion.
b) It involves the use of energy in the form of active transport.
c) It is driven by the concentration gradient alone.
d) It relies on the random movement of ions.

Answer 1

The findings by Reuter and Seitz suggest active transport is involved in ion exchange in cells, as sodium and calcium ions are moved against their concentration gradients using energy, often from ATP. Secondary active transport also uses created gradients to move other substances.

Step-by-step explanation:

The experiment conducted by Harold Reuter and Norbert Seitz in 1968 suggests that the transport of ions in and out of cells involves the use of energy in the form of active transport. The proposed mechanism for the exchange of sodium and calcium ions indicates that cells actively regulate the movement of these ions. The sodium-potassium pump is a well-known example of active transport, using ATP to move ions against their concentration gradient. Moreover, secondary active transport (co-transport) can use the energy stored in the electrochemical gradient of sodium ions to transport other substances like glucose and amino acids.

Secondary active transport is a process where the movement of sodium ions creates an electrochemical gradient used to transport other substances. The energy used in this process essentially comes from primary active transport, which creates the initial gradient by moving sodium ions out of the cell. This process shows that ion transport is not solely based on passive processes like diffusion or driven only by a concentration gradient, but rather involves active mechanisms.