NCERT solutions for class 9 science : Intext Solutions

Chapter 05-Fundamental Unit of Life-Intext Solutions

Intext Questions-Page Number 59
Q.1. Who discovered cells and how?
Answer. Robert Hooke, by observing a thin section of cork under self-designed microscope.
Q.2. Why is the cell called structural and functional unit of life?
Answer. All living organisms are made up of cells and these cells perform all the functions essential for the survival of the organisms, e.g., respiration, digestion, excretion, etc. Thus, cell is the functional unit of life.
In unicellular organism, a single cell carries out all these functions and in multicellular organisms different groups of cells carry out different functions. Thus, cell is the structural unit of all living organisms.

Intext Questions Page Number 61
Q.1. How do substances like $CO_{2}$ and water move in and out of the cell? Discuss.
Answer. When concentration of carbon dioxide is more inside the cell than outside, $CO_{2}$ diffuses from the cell to outside of cell. If $CO_{2}$ concentration inside the cell is less, $CO_{2}$ moves inside the cell from outside.
The water moves in and out of the cell by the process of osmosis. Osmosis is the passage of water from a region of high water concentration to a region of low concentration of water through semi permeable membrane.
Q.2. Why is the plasma membrane called as selectively permeable membrane?
Answer. 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.
Intext Questions Page Number 63
Q.1. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells.

 

Answer. 2. Nuclear region: An undefined nuclear region and nuclear membrane is absent and known as nucleoid.
4. Nuclear membrane as well as membrane enclosed organelles present.
Intext Questions Page Number 61
Q.1. Can you name the two organelles we have studied that contain their own genetic material.
Answer. Mitochondria and plastids.
Q.2. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
Answer. The damaged cell will not be able to perform functions like respiration, obtaining nutrition and cleaning of waste materials or forming new proteins.
Q.3. Why are lysosomes known as suicidal bags?
Answer. Lysosomes are called suicidal bags because they secrete certain enzymes, which helps in digesting the dead cell organelles and sometimes they also cause the digestion of whole cell.
Q.4. Where are proteins synthesised inside the cell?
Answer. Ribosomes are the sites of protein synthesis.