1. What are cells, and why are they important?

Cells are the fundamental structural and functional units of living organisms. They are important because all living organisms are made up of cells, and cells perform essential functions like respiration and nutrition.

2. What is the difference between unicellular and multicellular organisms?

Unicellular organisms are made up of one cell, while multicellular organisms are made up of numerous cells. Examples of unicellular organisms include Amoeba, Chlamydomonas, Paramoecium, and bacteria, while examples of multicellular organisms include plants and animals.

3. What is division of labour in multicellular organisms?

In multicellular organisms, different groups of cells (tissues) are present, and each tissue performs specific functions. This is known as division of labour.

4. Who discovered cells and when?

Robert Hooke, an English scientist, saw cells for the first time in 1665 in a thin slice of cork taken from the bark of a tree (Quercus). He named these structures as cellular or cells.

5. What is the cell theory?

The cell theory was formulated by two German biologists: M.J. Schleiden, a botanist, and T. Schwann, a zoologist. According to this theory, all living organisms are made up of cells and their products, cell is the basic structural and functional unit of life, and all cells arise from pre-existing cells.

6. What is the plasma membrane?

The plasma membrane, also known as the cell membrane, is the outermost covering of the cell that separates the components of the cell from its external environment. It is a selectively permeable membrane made of a bilayer of phospholipids and proteins.

7. What is the role of plasma membrane?

The plasma membrane plays a vital role in providing flow of information among different cells of the same organism apart from being a mechanical barrier that protects the internal contents of the cell. It also regulates the movement of substances in and out of the cell.

8. What is diffusion?

Diffusion is a process in which substances move from their region of high concentration to a region of their low concentration.

9. What is osmosis?

Osmosis is a special type of diffusion in which the movement of water molecules occurs from the area of low solute concentration to the region of high solute concentration through a semi-permeable membrane.

10. What are the different types of osmotic solutions?

Osmotic solutions are of three types, namely hypotonic, isotonic, and hypertonic. In a hypotonic solution, water will enter into the cell, causing it to swell. In an isotonic solution, there is no net movement of water. In a hypertonic solution, water will move out of the cell, causing it to shrink.

11. What are the three parts of a nucleus?

The three parts of a nucleus are the nuclear envelope, nucleoplasm, and nucleolus.

12. What is the function of the nuclear envelope?

The nuclear envelope delimits the nucleus from the cytoplasm and is a double membranous covering. It is connected with the endoplasmic reticulum and has nuclear pores that facilitate the exchange of materials between nucleus and cytoplasm.

13. What is chromatin and what is its role in cell division?

Chromatin is a granular network of DNA and protein. During cell division, chromatin becomes highly condensed, thick and rod-like structures, known as chromosomes. Chromosomes contain information for inheritance of characters from parents to offspring

14. What is cytoplasm and what are its two parts?

Cytoplasm is the protoplasmic mass of the cell inner to plasma membrane and excluding nucleus. Its two parts are cytosol, the fluid viscous part of cytoplasm in which a number of metabolic reactions takes place, and cell organelles, submicroscopic structures that are specialized to perform specific cellular functions.

15. What is the difference between eukaryotic and prokaryotic cells?

Eukaryotic cells have a well-defined nucleus and membrane-bound cell organelles, while prokaryotic cells lack a nucleus and membrane-bound cell organelles.

16. What are the three types of cell organelles based on membranous covering?

The three types of cell organelles based on membranous covering are double membranous (mitochondria, plastids, golgi apparatus, endoplasmic reticulum), single membranous (lysosomes, vacuole), and non-membranous (ribosomes).

17. What is the function of mitochondria?

Mitochondria are rod-shaped or sausage-shaped cell organelles which are known as the powerhouse of the cell. They contain enzymes necessary for the oxidation of food during the process of respiration and for the release of energy in the form of ATP.

18. What is the role of endoplasmic reticulum?

18. What is the role of endoplasmic reticulum?

Endoplasmic reticulum consists of a large network of membrane-bound channels, tubules, and vesicles. It is the site of protein synthesis in the case of rough endoplasmic reticulum (RER), and it helps in lipid synthesis in the case of smooth endoplasmic reticulum (SER).

19. What is the function of lysosomes?

Lysosomes are small spherical vesicles covered by a single membrane which contains digestive enzymes for intracellular digestion and waste disposal. They play an important role in removing dead and worn-out cellular organelles, help in the destruction of foreign particles, and aid in intracellular digestion of food particles.