Class 9 Chapter 5 Cell

 Class 9 Chapter 5 Cell 

Q1: Who discovered the cell and when? A: Robert Hooke discovered the cell in 1665 by observing a thin slice of cork under a self-designed microscope.

Q2: What does the word 'cell' mean? A: The word 'cell' is derived from a Latin word meaning a "little room".

Q3: Who was the first to discover free-living cells? A: Leeuwenhoek (1674) was the first to discover free-living cells in pond water using an improved microscope.

Q4: Who coined the term 'protoplasm'? A: J.E. Purkinje (1839) coined the term 'protoplasm' for the fluid biological substance found within the cell.

Q5: Who proposed the cell theory? A: Two biologists, M. Schleiden (1838) and T. Schwann (1839), proposed the cell theory, which was later expanded by Virchow (1855) who stated that all cells arise from pre-existing cells.

Q6: What is the plasma membrane also known as and why? A: The plasma membrane is known as a selectively permeable membrane because it permits or restricts the entry and exit of specific materials in and out of the cell.

Q7: What is the main component of a plant cell wall? A: The plant cell wall is mainly composed of cellulose, a complex substance that provides structural strength to plants.

Q8: What is plasmolysis? A: When a living plant cell loses water through osmosis, there is a shrinkage or contraction of the inner contents away from the cell wall, a phenomenon known as plasmolysis.

Q9: What are the functional segments of DNA called? A: The functional segments of DNA are called genes.

Q10: What are chromosomes composed of? A: Chromosomes are composed of DNA and proteins.

Q11: What is membrane biogenesis? A: The process by which some proteins and lipids (synthesized by the Endoplasmic Reticulum) help in building the cell membrane is called membrane biogenesis.

Q12: Which cell organelle is called the 'suicide bag'? A: Lysosomes are known as the 'suicide bags' of a cell because if the cell gets damaged, they can burst and their powerful digestive enzymes end up digesting their own cell.

Q13: Why are mitochondria known as the 'powerhouse' of the cell? A: Mitochondria are the powerhouse of the cell because they provide the energy required for various life activities in the form of ATP (Adenosine Triphosphate).

Q14: Name two cell organelles that contain their own DNA and ribosomes. A: Mitochondria and Plastids are two unique organelles that possess their own DNA and ribosomes.

Q15: What are the two types of plastids found in plant cells? A: The two types of plastids are chromoplasts (colored plastids, like chloroplasts which contain chlorophyll) and leucoplasts (colorless or white plastids primarily used for storing starch, oils, and proteins).

Q16: Which type of cell division is responsible for growth and tissue repair? A: Mitosis is the cell division responsible for the growth and repair of tissues, where a mother cell divides to form two identical daughter cells.

Q17: Which type of cell division is used to form gametes? A: Meiosis is the specialized cell division that forms gametes in reproductive organs, resulting in new cells that have half the number of chromosomes compared to the mother cell.