CBSE Class 11 Biology Very Short Answer Questions: Cell – The Unit of Life (NCERT-Based)

Course and Examination Framework

Course: CBSE Class 11 Biology

Board: Central Board of Secondary Education

Unit III: Cell Structure and Function

Chapter 8: Cell – The Unit of Life

Question Type: Very Short Answer Questions (VSA)

Answer Length: 20–30 Words

Syllabus: Strictly as per NCERT

Exam Relevance: CBSE Class 11 Annual & School Examinations

Section A: Cell Discovery and Cell Theory (Questions 1–10)

Q1. Who discovered the cell and in which year?
Ans: Robert Hooke discovered the cell in 1665 while observing thin slices of cork under a compound microscope.

Q2. What is cytology?
Ans: Cytology is the branch of biology that deals with the study of cells, including their structure, function, and composition.

Q3. State the cell theory.
Ans: Cell theory states that all living organisms are composed of cells, the cell is the basic unit of life, and new cells arise from pre-existing cells.

Q4. Who proposed the cell theory?
Ans: The cell theory was proposed by Matthias Schleiden and Theodor Schwann.

Q5. Who added the third postulate to cell theory?
Ans: Rudolf Virchow added the postulate that all cells arise from pre-existing cells.

Q6. Why is the cell called the basic unit of life?
Ans: The cell performs all vital functions such as metabolism, growth, respiration, and reproduction, making it the basic unit of life.

Q7. Name the first living cell observed.
Ans: Antonie van Leeuwenhoek first observed living cells using improved microscopes.

Q8. What is the significance of cell theory?
Ans: Cell theory explains the unity of life and establishes the cellular basis of all biological processes.

Q9. Define unicellular organism.
Ans: A unicellular organism consists of a single cell that performs all life functions independently.

Q10. Give one example of a unicellular organism.
Ans: Amoeba is an example of a unicellular organism.

Section B: Prokaryotic and Eukaryotic Cells (Questions 11–20)

Q11. What is a prokaryotic cell?
Ans: A prokaryotic cell lacks a true nucleus and membrane-bound organelles, with genetic material present in a nucleoid region.

Q12. Give two examples of prokaryotic organisms.
Ans: Bacteria and cyanobacteria are examples of prokaryotic organisms.

Q13. What is a eukaryotic cell?
Ans: A eukaryotic cell has a true nucleus enclosed by a nuclear membrane and contains membrane-bound organelles.

Q14. Name two eukaryotic organisms.
Ans: Plants and animals are eukaryotic organisms.

Q15. What is nucleoid?
Ans: Nucleoid is the irregular region in prokaryotic cells containing naked circular DNA without a nuclear membrane.

Q16. State one difference between prokaryotic and eukaryotic cells.
Ans: Prokaryotic cells lack membrane-bound organelles, whereas eukaryotic cells possess membrane-bound organelles.

Q17. What type of ribosomes are found in prokaryotic cells?
Ans: Prokaryotic cells contain 70S ribosomes.

Q18. Which ribosomes are found in eukaryotic cytoplasm?
Ans: Eukaryotic cytoplasm contains 80S ribosomes.

Q19. Name the genetic material in eukaryotic cells.
Ans: Linear DNA associated with histone proteins forms chromosomes in eukaryotic cells.

Q20. What is glycocalyx?
Ans: Glycocalyx is the outer protective covering found in some prokaryotic cells.

Section C: Cell Membrane and Cell Wall (Questions 21–30)

Q21. What is the plasma membrane?
Ans: Plasma membrane is a selectively permeable membrane that surrounds the cell and regulates movement of substances.

Q22. Which model explains the structure of plasma membrane?
Ans: The Fluid Mosaic Model explains the structure of the plasma membrane.

Q23. Name the components of plasma membrane.
Ans: Plasma membrane is composed of phospholipids, proteins, and carbohydrates.

Q24. What is selective permeability?
Ans: Selective permeability is the ability of plasma membrane to allow some substances to pass while restricting others.

Q25. Define diffusion.
Ans: Diffusion is the passive movement of molecules from higher concentration to lower concentration.

Q26. What is active transport?
Ans: Active transport is the movement of substances across the membrane against concentration gradient using energy.

Q27. What is endocytosis?
Ans: Endocytosis is the process by which cells engulf substances through the plasma membrane.

Q28. Where is cell wall found?
Ans: Cell wall is found in plant cells, fungi, and bacteria but absent in animal cells.

Q29. Name the main component of plant cell wall.
Ans: Cellulose is the main structural component of the plant cell wall.

Q30. State one function of cell wall.
Ans: Cell wall provides rigidity, protection, and prevents osmotic bursting of plant cells.

Section D: Cell Organelles (Questions 31–50)

Q31. What is the nucleus?
Ans: The nucleus is a membrane-bound organelle that contains genetic material and controls cellular activities.

Q32. Name the double membrane of nucleus.
Ans: Nuclear envelope is the double membrane surrounding the nucleus.

Q33. What is nucleolus?
Ans: Nucleolus is a dense structure inside the nucleus involved in ribosome formation.

Q34. Define endoplasmic reticulum.
Ans: Endoplasmic reticulum is a network of membranous tubules involved in synthesis and transport of biomolecules.

Q35. Differentiate RER and SER in one sentence.
Ans: RER synthesizes proteins, while SER synthesizes lipids and helps in detoxification.

Q36. What is Golgi apparatus?
Ans: Golgi apparatus is a membrane-bound organelle involved in modification, packaging, and secretion of proteins.

Q37. Why are lysosomes called suicidal bags?
Ans: Lysosomes contain hydrolytic enzymes that can digest damaged organelles and cause cell autolysis.

Q38. State one function of mitochondria.
Ans: Mitochondria produce ATP through aerobic respiration.

Q39. Why are mitochondria called powerhouse of the cell?
Ans: They generate energy-rich ATP molecules required for cellular activities.

Q40. Name the site of photosynthesis in plant cells.
Ans: Chloroplast is the site of photosynthesis in plant cells.

Q41. What are plastids?
Ans: Plastids are double-membraned organelles in plant cells involved in photosynthesis, storage, and coloration.

Q42. Name three types of plastids.
Ans: Chloroplasts, chromoplasts, and leucoplasts are the three types of plastids.

Q43. What is the function of ribosomes?
Ans: Ribosomes are the sites of protein synthesis.

Q44. Are ribosomes membrane-bound?
Ans: Ribosomes are non-membranous organelles.

Q45. What is cytoskeleton?
Ans: Cytoskeleton is a network of protein filaments that maintains cell shape and enables movement.

Q46. What is centrosome?
Ans: Centrosome is an organelle found in animal cells involved in spindle formation during cell division.

Q47. Name the structural arrangement of cilia and flagella.
Ans: Cilia and flagella have a 9+2 arrangement of microtubules.

Q48. What is vacuole?
Ans: Vacuole is a membrane-bound sac involved in storage and maintenance of cell turgidity.

Q49. Which cell has a large central vacuole?
Ans: Plant cells possess a large central vacuole.

Q50. Name two organelles having their own DNA.
Ans: Mitochondria and chloroplasts have their own DNA.