Class 11 Biology Important Chapter 8 Cell: The Unit of life

Class 11 Biology Important Chapter 8 Cell: The Unit of life Solutions English Medium As Per AHSEC New Syllabus to each chapter is provided in the list so that you can easily browse through different chapters ASSEB Class 11 Biology Important Solutions and select need one. AHSEC Class 11 Biology Additional Notes English Medium Download PDF. HS 1st Year Biology Important Solutions in English.

Class 11 Biology Important Chapter 8 Cell: The Unit of life

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Cell: The Unit of life

Chapter: 8

IMPORTANT QUESTION AND ANSWER

Very Short and Short Answer Type Question: 

1. Define a cell.

Ans: Cell is defined “as the structural and functional unit of the organism.”

2. What is the major function of SER.

Ans: SER is engaged in the synthesis and storage of glycogen, fat and sterols.

3. Who discovered the nucleus?

Ans: Robert Brown.

4. What is the full form of PPLO?

Ans: Pleuro Pneumonia Like Organisms.

5. Who proposed the cell theory?

Ans: Schleiden and Schwann (1838-1839).

6. Name some unicellular organisms.

Ans: Amoeba, Paramecium, Euglena.

7. Which organelle is considered as the ‘power house of the cell’?

Ans. Mitochondrion.

8. Which structure is called little nucleus?

Ans. The nucleolus.

9. Give the chemical composition of biomembrane.

Ans: Proteins, lipids, carbohydrates and enzymes.

10. What are the basic shapes of bacteria?

Ans: Bacillus, Coccus, Vibrio, Spirillum.

11. What is meant by cell theory? Who contributed to it?

Ans: The cell theory is a fundamental concept in biology which explains the structure and origin of all living organisms. According to this theory, all living organisms are composed of cells and their products, and all cells arise from pre-existing cells. This concept emphasizes that the cell is the basic structural and functional unit of life. The theory was initially proposed by Matthias Schleiden, a German botanist, and Theodor Schwann, a German zoologist. Later, in 1855, Rudolf Virchow modified their hypothesis by adding that all cells arise from pre-existing cells (Omnis cellula e cellula), giving the cell theory its present form.

12. What is the significance of the plasma membrane?

Ans: The cell membrane or plasma membrane. It is in extremely thin membrane. It is also called as plasmalemma. It is present as an outer covering of animal cells. In plant cells, it is present below the cell wall surrounding the protoplasm of the cell. 

Significance of Plasma membrane:

(i) It forms the outer boundary of the cell. Thus it helps in giving cell a definite shape.

(ii) It protects the inner contents of the cell.

(iii) It allows the passage of excreta substances through it. Hence it acts as a selectively permeable membrane.

(iv) It forms a molecular boundary between cell and its environment.

13. What structural and functional characteristics of cilia, flagella and centrioles have in common?

Ans. The common structural feature of cilia, flagella and centriole is that all of them have basal bodies as starting point which has (9 + 2) arrangement of triplets of microtubules. Functionally, they show contraction and expansion causing movement or migration.

14. What are histones. What are their function?

Ans: Histones are basic (alkaline) proteins found in the nucleus of eukaryotic cells. They are rich in amino acids like lysine and arginine and are positively charged, which helps them bind with the negatively charged DNA.

Their primary function is to package and organize DNA into structural units called nucleosomes, enabling efficient DNA condensation within the nucleus. By wrapping DNA around themselves, histones help in DNA compaction and also play a crucial role in regulating gene expression, replication, and repair processes.

15. Which organelle is responsible for increasing the surface area of absorption in a cell?

Ans. The endoplasmic reticulum: It remains in the form of convoluted tubule in the cytoplasm in the form of a network. This provides more area for chemical reaction and increases the surface area of absorption.