The Fundamental Unit of Life – Class 9 Biology Chapter 1

Practice and learn the important question of chapter 1 of Biology Class 9- The fundamental unit of life. The chapter is the most basic and the easiest one of Biology. Since the chapter carries a good weightage in the exam, the students can easily score maximum marks in this chapter. NTSE Guru Experts have designed the most probable questions that are likely to appear in the exams. Start your class 9th exam preparation today with these questions and answers of chapter 1 of Biology.

Important Questions of  the Chapter – The Fundamental Unit of Life

1.  When and by whom was cell discovered?

Ans. Cell was discovered in 1665 by Robert Hooke.

 2. Who gave cell theory? Write down the various postulates of cell theory. Who extended this theory and when.

Ans.  Cell theory was given by – Matthias Schleiden and Theodor Schwann.

It states that –

       1)   All organisms are composed of cells and cell products.

2)   All metabolic reactions take place in cell. Thus, cell is the basic structural and functional unit of life.

3)   Every organism starts its life as a single cell.

       4)   It was extended by Rudolf Virchow in 1855. He stated that:

       All cells arise from pre-existing cells.

3. Differentiate between unicellular organism and multicellular organism.

Ans.                    

Unicellular Organism Multicellular Organism
1. Uni = Single Multi = Many

2. Organism with single cell

With many cell
3. Division of labour absent Division of labour present
4. Simple organism Comparatively complex
E.g., Amoeba, Paramecium E.g., Human, Cat

4. What is plasma membrane? State the composition and function of the same.

Ans. Plasma membrane is the outermost covering of animal cell and second most outer covering in plant cell.

       It is made up of lipoproteins and phospholipids.

Function –

(i) It gives shape and structure to the cell.

(ii) It protects the internal cell organelle.

(iii) It checks transport of materials.

5. Mention the significance of osmosis and diffusion.

Ans.  i) Diffusion helps in exchange of gases whereas, Osmosis helps in exchange of water especially in aquatic organism.

 ii) Osmosis helps in absorption of water in plant.

        iii)     Osmosis regulates opening and closing of stomata.

 6. Give examples to explain:

 1) Hypertonic        2) Isotonic and          3) Hypotonic solutions

Ans. 1)  If the solution has lower concentration of water than the cell i.e., it is very concentrated solution, the cell will lose water by osmosis. Such a concentrated solution is called – hypertonic solution.

 2)  If the medium surrounding the cell is of the same water concentration as the cell, there will be no net movement of water across the plasma membrane. Such a solution is called – Isotonic solution.

 3)  If the medium surrounding the cell has a higher water concentration than the cell i.e., if solution is a very dilute solution, the cell will gain water by osmosis, such a solution is called hypotonic solution.

7. What is the difference between a cell wall and a plasma membrane?

Ans. 

Cell Wall Cell Membrane
1) It is the outermost thick layer present in plant cell. It is outside the plasma membrane. 1) It is the outermost layer of animal cell and second layer of plant cells.
2) It is freely permeable to water and substances in solution. 2) It is semi-permeable in nature.
3) It is made up of cellulose. 3) It is made up of phospholipids and lipoprotein.
4)   It gives mechanical support and shape to plant cell. 4)  It gives protection and support to inner cell organelles.
5)  It is dead. 5)  It is living.

8. What is a eukaryotic cell?

Ans. ‘Eu’ means true and ‘Karyon’ means nucleus. Cells with true nucleus, i.e., definite nucleus with nuclear membrane are called eukaryotic cell.

It also contains membrane – bound organelles in its cytoplasm, e.g., Endoplasmic reticulum, Golgi body, mitochondria, etc.

9.  What is nucleoid?

Ans. In prokaryotic cell the nuclear region containing chromatin material but not bound by nuclear membrane is called nucleoid (under-developed Nucleus).

10.  Name the following cell organelles and write their function:

1) An organelle which is suicidal bag.

2) An organelle which is secretory.

3) An organelle which is power house of cell

4) An organelle which is kitchen of cell

5) An organelle which provide color to the cell.

Ans. 1) Lysosome → help in digestion of protein, carbohydrates, lipids, etc.

2) Golgi bodies → packing, storing, modifying protein

       3) Mitochondria → formation of ATP

       4) Chloroplast → formation of glucose

       5) Chromoplast → (Plastid) Imparts color to plant parts and cells

 11. What is known as the energy currency of a cell? Why?

Ans. Energy currency of cell is ATP (Adenosine triphosphate) because it is required to perform vital functions in cell.

12. Name the types of plastids found in plant cell and also write their function.

Ans. Types of plastids –

(1)   Chloroplast Green in color due to presence of chlorophyll, helps in photosynthesis by absorption of light.

(2)   Chromoplast  – Red, Yellow or orange in color, gives colors to flowers, fruits and vegetables.

(3)   Leucoplast White in color, stores lipids, proteins and carbohydrates found in roots, grains, etc.

13. What are vacuoles? What are the substances stored in it?

Ans.  A fluid filled single-membrane organelle present mainly in plant cells. The substances stored in it are: Water, salt, sugar, pigments, wastes, gases, etc.

14.  (a) Golgi apparatus has a system of membrane bound vesicles arranged in parallel stacks. What are these called?

       (b)  What are the functions of golgi apparatus?

Ans.  (a)   Cisternae.

       (b)   Function of Golgi apparatus are:

(i)    Packing and dispatching of materials.

(ii)   Biogenesis of cell membrane, cell wall, lysosome

(iii)  Secretion

(iv)  Formation of cell plate in plant cells.

15. Name two cell organelles which are found in plant cell but absent in animal cells.

Ans. Two cell organelles which are found in plant cells but absent in animal cells are polar cap (counterpart of centriole of animal cell) and plastids.

If you want such more important questions for other subjects, click here: Chapter-wise important questions

Leave a Reply

Your email address will not be published. Required fields are marked *