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Science & Technology General Science
Q.

 Consider the following statements:

1. Some substances like carbon dioxide or oxygen can move across the cell membrane by a process called Osmosis. 

2. In the cell’s external environment, the concentration of carbon dioxide is low as compared to that inside the cell.

Which of the statement(s) given above is/are correct?
Explanation:

ANSWER: (B)

  • Statement 1 is not correct.

Some substances like carbon dioxide or oxygen can move across the cell membrane by a process called diffusion. Under this process, there is spontaneous movement of a substance from a region of high concentration to a region where its concentration is low. As soon as there is a difference of concentration of CO2 inside and outside a cell, CO2 moves out of the cell, from a region of high concentration, to a region of low concentration outside the cell by the process of diffusion. 

Similarly, O2 enters the cell by the process of diffusion when the level or concentration of O2 inside the cell decreases. Thus, diffusion plays an important role in gaseous exchange between the cells as well as the cell and its external environment. Water also obeys the law of diffusion. The movement of water molecules through such a selectively permeable membrane is called osmosis.

  • Statement 2 is correct.

Something similar to this happens in cells when, for example, some substance like CO2 (which is cellular waste and requires to be excreted out by the cell) accumulates in high concentrations inside the cell. In the cell’s external environment, the concentration of CO2 is low as compared to that inside the cell. 

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