Question

During transport of sugar or amino acid into the cell through cell membrane

• A. Na${}^{+}$ ions move against the direction of concentration gradient
• B. Na${}^{+}$ ions move in both direction irrespective concentration of its gradient
• C. No net Na${}^{+}$ ions movement
• D. Na${}^{+}$ ions move in the direction of its concentration gradient

Answer 1

The correct option is D Na${}^{+}$ ions move in the direction of its concentration gradient

The cell membrane plays an important role in the transport of molecules. Because it acts as a semi-permeable barrier, allowing only specific molecules to cross. The movements of solutes into the cell are mediated through the action of specific transport proteins that are present in the cell membrane. Such proteins are required for movements of ions, such as Na${}^{+}$, K${}^{+}$, Ca${}^{2+}$ and Cl${}^{-}$, as well as metabolites such as pyruvate, amino acids, sugars, and nucleotides, and even water.

Facilitated diffusion is the movement of a substance along the concentration gradient (i.e. from high to low concentration). Example: Glucose symporter, which co-transports one glucose molecule into the cell for every two sodium ions it imports into the cell.

So, the answer is A.