NCERT Class 9 Science Solutions: Chapter 5 –The Fundamental Unit Of Life Part 1

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Question 1:

Q. Who discovered cells and how?

Image of Discovered Cells for The Fundamental Unit of LIfe

Cells as the Fundamental Unit of LIfe

Image of Discovered Cells for The Fundamental Unit of LIfe

A. Cells were discovered in 1665 by an English Botanist, Robert Hooke. He used a primitive microscope to observe cells in a thin slice of cork.

Question 2:

Q. Why is the cell called the structural and functional unit of life?

A. Cells constitute various components of plants and animals. A cell is the smallest unit of life and is capable of all living functions. Cells ae the building blocks of life. This is the reason why cells are referred to as the basic structural and functional units of life. All cells vary in their shape, size and activity they perform. In fact, the shape and size of the cell is related to the specific functions they perform.

Question 1:

Q. How do substances like and water move in and out of the cell? Discuss.

Image of CO2 and Water Move in and Out of the Cell for The Fundamental Unit of Life

CO2 and Water Move in and Out of the Cell

Image of CO2 and Water Move in and Out of the Cell for The Fundamental Unit of Life

A. The cell membrane is selectively permeable and regulates the movement of substances in and out of the cell.

Movement of :

is produced during cellular respiration. Therefore, it is present in high concentrations inside the cell. This must be excreted out of the cell. In the cell’s external environment, the concentration of is low as compared to that inside the cell. Therefore, according to the principle of diffusion, moves from a region of higher concentration (inside the cell) towards a region of lower concentration (outside the cell). Similarly, enters the cell by the process of diffusion when the concentration of inside the cell is low as compared to its surroundings.

Movement of Water:

Water moves from a region of high concentration to a region of low concentration through the plasma membrane. The plasma membrane acts as a semi-permeable membrane, and this movement of water is known as osmosis. However, the movement of water across the plasma membrane of the cell affected by the amount of substance dissolved in water.

Question 2:

Q. Why is the plasma membrane called a selectively permeable membrane?

A. The cell membrane or the plasma membrane is known as a selectively permeable membrane because it regulates the movement of substances in and out of the cell. This means that the plasma membrane allows the entry of only some substances and prevents the movement of some other materials.