Question

Question 14. Match the transport process to the correct description or example. Secondary Active Transport is:

1. transport of sodium out of a neuron
2. transport of glucose into a cell, against its concentration gradient
3. transport of glucose out of cell, with its concentration gradient
4. transport of a steroid hormone into a cell
5. transport of large macromolecules into a cell
6. transport of signal molecules out of an endocrine cell
7. making a new covalent bond
8. import of an entire bacterium into a white blood cell
9. breaking of a covalent bond to create new molecules

Answer 1

Answer

B) transport of glucose into a cell, against its concentration gradient

Explanation :- Secondary active Transport :

When sodium ions are transported out of cells by primary active transport, a large concentration gradient of sodium ions across the cell membrane develops high concentration outside the cell and very low concentration inside.This gradient represents a storehouse of energy because the excessive sodium outside the cell membrane attempts to diffuse to the interior. Under appropriate conditions, this diffusion energy of sodium can pull other substances along with the sodium through the cell membrane. This phenomenon is called co-transport; it is one form of secondary active transport.

For sodium to pull another substance along with it, a coupling mechanism is required. This is achieved by means of still another carrier protein in the cell membrane.

The carrier in this instance serves as an attachment point for both the sodium ion and the substance to be co-transported. Once they both are attached, the energy gradient of the sodium ion causes both the sodium ion and the other substance to be transported together to the interior of the cell.

Co-Transport of Glucose and Amino Acids:

Along with Sodium Ions Glucose and many amino acids are transported into most cells against large concentration gradients; the

mechanism of this is entirely by co-transport, as. the transport carrier protein has two binding sites on its exterior side, one for sodium and one for glucose.Also, the concentration of sodium ions is very high on the outside and very low inside, which provides energy for the transport. A special property of the transport protein is that a conformational change to allow sodium movement to the interior will not occur until a glucose molecule also attaches. When they both become attached, the conformational change takes place automatically, and the sodium and glucose are transported to the inside of the cell at the same time. Hence, this is a sodium-glucose

co-transport mechanism.