Ch 2 :- Cell: The Building Block of Life
Important Questions and Answers
Ques 1 :- Differentiate between plant and animal cell.
Ans:-
| Features | Plant Cell | Animal Cell |
|---|---|---|
| Cell Shape | Square or rectangular in shape | Irregular or round in shape |
| Cell Wall | Present | Absent |
| Nucleus | Present and lies on one side of the cell | Present and lies in the centre of the cell |
| Plastids | Present | Absent |
| Vacuoles | Few large or a single, centrally positioned vacuole | Usually small and numerous |
| Mode of Nutrition | Primarily autotrophic | Heterotrophic |
| Cilia | Absent | Present in most animal cells |
| Mitochondria | Present but fewer in number | Present and more numerous |
Ques 2 :- Differentiate between Prokaryotic Cell and Eukaryotic Cell.
| Features | Prokaryotes | Eukaryotes |
|---|---|---|
| Type of Cell | Always unicellular | Unicellular or multicellular |
| Nucleus | Absent. DNA floats freely in a region called the nucleoid. | Present. DNA is enclosed within a true, double-membrane nucleus. |
| Cell Organelles | Membrane-bound organelles are absent. | Membrane-bound organelles are present and perform specific functions. |
| Reproduction | Asexual | Both asexual and sexual |
| DNA Arrangement | Circular | Linear |
| Mitochondria | Absent | Present |
| Endoplasmic Reticulum | Absent | Present |
| Plasmids | Present | Very rarely found |
| Example | Bacteria and Archaea | Plant and Animal cells |
Ques 3 :- Describe the structural and functional features of cells.
Ans:- Cells are the basic structural and functional units of life. Their structural and functional features are as follows:
Structural Features
• Cells are enclosed by a cell membrane that separates them from the external environment.
• Most cells have a nucleus that controls cellular activities.
• Plant cells possess a cell wall , chloroplasts, and a large vacuole.
Functional Features
• Cells perform all vital life processes such as nutrition, respiration, excretion, and reproduction.
• The nucleus controls and coordinates all activities of the cell.
• Mitochondria release energy required for cellular functions.
• Cells help in the growth, repair, and maintenance of the organism.
Therefore, cells provide structure to living organisms and carry out all essential life processes
Ques 4 :- Why is the Cell Called the Structural and Functional Unit of Life?
Ans:- A cell is called the structural unit of life because all living organisms are made up of cells. Cells combine to form tissues, tissues form organs, and organs form organ systems. Thus, cells provide the basic structure and shape of an organism.
A cell is called the functional unit of life because all vital life processes such as nutrition, respiration, excretion, growth, and reproduction take place within cells. The proper functioning of cells ensures the survival and functioning of the entire organism.
Therefore, the cell is the basic structural and functional unit of life because it forms the body of an organism and carries out all essential life processes.
Ques 5 :- Differentiate between Osmosis and Diffusion ?
Ans:-
| Osmosis | Diffusion |
|---|---|
| ➜ It is a special type of diffusion involving only water molecules. | ➜ It is a general process involving the movement of any particles. |
| ➜ Commonly occurs in living cells and biological systems. | ➜ Occurs in both living and non-living systems. |
| ➜ Helps in water absorption by plant roots and maintaining cell turgidity. | ➜ Helps in the exchange of gases and spreading of substances. |
| ➜ The rate depends on the water potential difference. | ➜ The rate depends on the concentration gradient. |
| ➜ Example: Movement of water into raisin cells placed in water. | ➜ Example: Spread of perfume fragrance in a room. |
Ques 6 :- Explain the role of cell division mitosis and meiosis in creating similarities and variations ?
Ans:- Cell division plays an important role in creating both similarities and variations among organisms.
• Mitosis produces two genetically identical daughter cells. It helps in growth, repair, and replacement of worn-out cells. Since the daughter cells are identical to the parent cell, mitosis maintains similarities between cells and organisms.
• Meiosis produces gametes (sex cells) with half the number of chromosomes. During meiosis, genetic material is exchanged and chromosomes are shuffled, resulting in new combinations of genes. This creates variations among offspring.
Therefore, mitosis maintains genetic continuity and similarities, while meiosis generates genetic variations that are important for evolution and adaptation.
Ques 7 :- Identify and describe the role of bio molecules in the structure and function of cell ?
Ans:- Biomolecules are the chemical substances present in cells that help in maintaining their structure and performing various functions. The main biomolecules are carbohydrates, proteins, lipids, and nucleic acids.
• Carbohydrates provide energy for cellular activities.
• Proteins help in building cell structures and carry out various functions such as enzyme activity.
• Lipids form an important part of the cell membrane and store energy.
• Nucleic acids (DNA and RNA) store and transmit genetic information and control cellular activities.
Therefore, biomolecules are essential for the structure, growth, maintenance, and proper functioning of cells.
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