1. Who discovered cells, and how?
Ans:In 1665, Robert Hooke discovered cells while examining a thin slice of cork through a self-designed microscope. He observed that the cork resembled the structure of a honeycomb consisting of numerous tiny compartments. The minuscule boxes are referred to as cells.
2. Why is the cell called the structural and functional unit of life?
Ans:Cells form the structure of an entity. A group of cells forms a tissue, which further forms an organ, and ultimately an organ system. They perform essential life functions like respiration, digestion, excretion, etc., in both unicellular and multicellular organisms. Cells perform all activities independently, making them the structural and functional units of life.
3. How do substances like CO2 and water move in and out of the cell?
Ans: CO2 moves by diffusion, from a higher concentration in the cell to a lower concentration outside. Water moves by osmosis through the selectively permeable membrane, from a region of higher concentration to a region of lower concentration, until equilibrium is reached.
4. Why is the plasma membrane called a selectively permeable membrane?
Ans:The plasma membrane is called selectively permeable because it allows the movement of certain molecules in and out of the cell while restricting others. This selective movement helps the cell maintain homeostasis.
5. Fill in the gaps in the following table, illustrating the differences between prokaryotic and eukaryotic cells.
6. Can you name the two organelles we have studied that contain their own genetic material?
Ans:The two organelles that contain their own genetic material are:
Mitochondria
Plastids
7. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
Ans:If the cell is damaged and cannot revive, lysosomes burst, releasing enzymes that digest the cell. This process is known as autolysis, where the cell breaks down itself.
8. Why are lysosomes known as suicide bags?
Ans:Lysosomes are known as “suicide bags” because, in cases of severe damage to the cell, they may rupture and release digestive enzymes that break down and destroy the cell.
9. Where are proteins synthesized inside the cell?
Ans:Proteins are synthesized in ribosomes, which are located on the rough endoplasmic reticulum (ER) or free in the cytoplasm. Ribosomes are also known as protein factories.