NEET Biology Chapter 1 The Fundamental Unit Of Life Question And Answers
Question 1. Who discovered cells and how?
Answer:
Discovery Of Cell:
Cell was discovered by Robert Hooke in 1665 while studying a thin slice of cork through a crude microscope. He observed that cork resembled the structure of a honeycomb having many small compartments. These compartments were later known as cells.
Question 2. Why cell is called the structural and functional unit of life?
Answer: Cells are called the structural and functional unit of life because all living organisms are made up of cells. These cells carried out specific functions which is important for life processes.
Question 3. Write the main postulates of cell theory. Who propounded the cell theory?
Answer:
Rudolf Virchow propounded the concept of cell theory and gave the idea that all cells arise from pre-existing cells.
The main postulates of the modern cell theory are as follows.
- All organisms are made up of one or more cells and cell products.
- All metabolic reactions occur in cells. Hence, cells are structural and functional units of life.
- All cells arise from pre-existing cells, as an animal gives birth only to an animal and a plant gives rise only to a plant.
- An organism begins its life as a single cell.
Question 4. Differentiate between prokaryotic and eukaryotic cells.
Answer:
Difference between prokaryotic and eukaryotic cells
Question 5. What is chromatin?
Answer:
Chromatin
The chromatin is a thin, thread-like entangled mass of chromosome material and it consists of the genetic material DNA and proteins (i.e., histones). The chromatin is formed of repeating subunits called nucleosomes.
Question 6. What is plasmodesmata?
Answer:
Plasmodesmata
Cell wall consists of narrow pores known as pits through which very fine strands of cytoplasm known as plasmodesmata.
Question 7. Which organelle is known as the powerhouse of the cell and why?
Answer: Mitochondria is known as the powerhouse of cells because the energy required for various chemical activities needed to support life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules.
Question 8. Where do the lipids and proteins constituting the cell membrane gets synthesized?
Answer: Lipids are synthesized in smooth endoplasmic reticulum and the proteins are synthesized in endoplasmic reticulum.
Question 9. What are nuclear pores?
Answer:
Nuclear pores
The nuclear envelope makes the nucleus distinct from cytoplasm. It also contains many pores called nuclear pores and it consists of the liquid ground substance called nucleoplasm.
Question 10. What are the functions of nucleus?
Answer:
The functions of nucleus are
- Nucleus controls all metabolic activity of the cell.
- Nucleus regulates the cell cycle.
- Nucleus controls the transmission of hereditary characteristics from the parent to offspring.
Question 11. Name the following.
(a) Outer most layer of the cell wall connecting the two adjoining cells.
(b) Cell membrane is chemically made up of
(c) Fold of plasma membrane in bacterial cells.
(d) Component which is considered as dynamic part of cell.
(e) What happens to cell when placed in salt solution?
(f) Who proposed fluid mosaic model?
Answer: (a) Middle lamella (b) protein (c) mesosomes (d) nucleus (e) cell swells (f) S. J. Singer and G. L. Nicolson (1972)
Question 12. Define phagocytosis.
Answer:
Phagocytosis
Intake of solid material by evagination of cell membrane on the periphery is known as phagocytosis.
Question 13. Define active transport.
Answer:
Active transport
Active transport is a speedy process. Diffusion is a slow process. This transport can move substances through a biological membrane against the concentration gradient and it is unidirectional in nature.
Question 14. Define exocytosis.
Answer:
Exocytosis
Exocytosis is the process by which the intracellular vesicles in the cytoplasm fuse with the plasma membrane and release their contents into the surrounding medium.
Question 15. Differentiate between diffusion and osmosis.
Answer:
Difference between diffusion and osmosis
