Question

3.How do cells overcome the energy requirement of active transport?

Answer 1

Active transport uses energy stored in ATP to fuel the transport. Active transport of small molecular-size material uses integral proteins in the cell membrane to move the material—these proteins are analogous to pumps..To move substances against a concentration or electrochemical gradient, a cell must use energy. Active transport mechanisms do just this, expending energy (often in the form of ATP) to maintain the right concentrations of ions and molecules in living cells. In fact, cells spend much of the energy they harvest in metabolism to keep their active transport processes running. For instance, most of a red blood cell’s energy is used to maintain internal sodium and potassium levels that differ from those of the surrounding environment.

Active transport mechanisms can be divided into two categories. Primary active transport directly uses a source of chemical energy (e.g., ATP) to move molecules across a membrane against their gradient. Secondary active transport (cotransport), on the other hand, uses an electrochemical gradient – generated by active transport – as an energy source to move molecules against their gradient, and thus does not directly require a chemical source of energy such as ATP. We’ll look at each type of active transport in greater detail below.

One of the most important pumps in animal cells is the sodium-potassium pump, which moves Na^++start superscript, plus, end superscript out of cells, and K^++start superscript, plus, end superscript into them. Because the transport process uses ATP as an energy source, it is considered an example of primary active transport.