Most Important Diagrams in Class 9 to practice for CBSE Class 9 Science Exam 2024. Simple Plasma Membrane Diagram Class 9 NCERT with Labels Easy Colour Drawing and Explanation.
Plasma Membrane Diagram Class 9 With Labels And Explanation
This is the outermost covering of the cell that separates the contents of the cell from its external environment. The plasma membrane allows or permits the entry and exit of some materials in and out of the cell. It also prevents movement of some other materials. The cell membrane, therefore, is called a selectively permeable membrane. How does the movement of substances take place into the cell? How do substances move out of the cell?
Some substances like carbon dioxide or oxygen can move across the cell membrane by a process called diffusion. We have studied the process of diffusion in earlier chapters. We saw that there is spontaneous movement of a substance from a region of high concentration to a region where its concentration is low. 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. 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.
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