Question

Secondary active transport (aka cotransport)

Answer 1

Secondary active transport is the cellular process where substances are moved across the plasma membrane using the energy of an electrochemical gradient created by primary active transport. It does not directly use ATP, but it is considered active transport because it leverages energy. Examples include sodium/glucose symport in the kidneys and hydrogen ion movement in mitochondria.

Step-by-step explanation:

Understanding Secondary Active Transport

Secondary active transport is a crucial cellular process occurring in the plasma membrane. It involves the movement of material against its concentration gradient (an endergonic process) coupled with another substance moving down its concentration gradient (an exergonic process). This form of transport does not directly require ATP, instead it relies on the electrochemical gradient established by primary active transport.

Primary active transport, which moves ions like sodium and potassium, is necessary to create this gradient. In secondary active transport, substances such as sodium ions and glucose enter the cell by utilizing the energy stored in these gradients. For example, in the kidneys, glucose reabsorption takes place through secondary active transport, where a sodium/glucose symporter uses the sodium gradient to move glucose against its own gradient into the cell.

There are two types of secondary active transport mechanisms: symport and antiport. Symport mechanisms transport substances in the same direction, while antiport mechanisms move them in opposite directions. An important use of secondary active transport is in the mitochondria where it helps generate ATP by the transport of hydrogen ions.

Answer 2

Secondary active transport is a biological process that moves substances against their concentration gradients by using the energy from an electrochemical gradient established by primary active transport. It involves symport and antiport mechanisms for molecule movement and is crucial for maintaining proper concentrations of substances within the body, as well as ATP synthesis in mitochondria.

Step-by-step explanation:

Understanding Secondary Active Transport

Secondary active transport, also known as cotransport, is a biological process where the energy from an electrochemical gradient, established by primary active transport, is used to move molecules across a cell membrane. This gradient is primarily created by the pumping of sodium ions out of the cell, which consumes ATP directly. Subsequently, as sodium ions naturally want to diffuse back into the cell, secondary active transport uses this opportunity to transport other substances, such as glucose or amino acids, into the cell against their concentration gradients.

This process can occur through symport mechanisms, where both sodium and another substance like glucose move in the same direction at the same time, or through antiport mechanisms, where they move in opposite directions. One example of secondary active transport is the reabsorption of glucose in the kidneys, where glucose is transported into cells along with sodium. Additionally, in the mitochondria, secondary active transport is vital for creating the hydrogen ion gradient used to convert ADP into ATP, a crucial energy currency in biological organisms.

Overall, while secondary active transport does not directly use ATP, it is still considered an active process because it relies on energy created from primary active transport. It is also an essential mechanism for maintaining the proper concentration of various substances within different parts of the body, including the renal tubules, gut, and various cellular membranes.