Question

Discuss the mechanism of primary active transport and provide an example of how it is used in the kidney.

Answer 1

Ans :

Mechanism of Primary Active Transport

Primary active transport also called direct active transport which directly uses chemical energy such as ATP in cell membrane to transport all sorts of solutes across a membrane against their concentration gradient. An example of this type of transport is (Na+/K+) ATPase pump on the basolateral cell membranes of the tubules. The sodium (Na+) concentration are lower inside the cell than outside whereas potassium (K+) concentration is greater inside the cell than outside. If it is a passive transport the ions will transport from higher to lower concentration. But with the expense of ATP, sodium is pumped out of the cell and at the same time potassium is moved into the cell. This is done by the primary active transport which utilize ATP to pump both (Na+ and K+) against the concentration gradient. Uptake of glucose in the human intestines is another example of primary active transport.

Active Transport in Kidney

Active transport can be seen in the kidneys, at the reabsorption stage in the nephrons. Kidneys are responsible for the filteration of blood to moveout waste from blood and also for the reabsorption of substances that required by the body from wastes. Along the nephron, a large network of capillaries surround the tubules that carry the waste. Substances that the body needs from the waste that can be re-used are reabsorbed into the blood stream. These substances are usually glucose, amino acids, vitamins, water and more. This reabsorption usually happens in the proximal and distal convoluted tubules and the loop of Henle. Since reabsorption of substances from wastes is against the concentration gradient, by the primary active transport mechanism the reabsorption process of the nutrients from wastes is taken place inside the kidney.