Organelles & Their Functions

Level 1: Recognition (MCQ, Matching & True/False with Justification)

Time Limit: 20 minutes Total Marks: 30

---

Section A — Multiple Choice (1 mark each) — 10 marks

Choose the ONE best answer.

Q1. Which organelle is the primary site of ribosome subunit assembly?

• (a) Golgi apparatus
• (b) Nucleolus
• (c) Smooth endoplasmic reticulum
• (d) Lysosome

Q2. The "9+2" arrangement of microtubules is a defining feature of:

• (a) Centrioles
• (b) Intermediate filaments
• (c) Cilia and flagella
• (d) Microvilli

Q3. Which structure is responsible for detoxification, lipid synthesis, and calcium ion storage?

• (a) Rough ER
• (b) Smooth ER
• (c) Nucleolus
• (d) Peroxisome

Q4. The infolded inner membrane of the mitochondrion is called the:

• (a) Thylakoid
• (b) Stroma
• (c) Cristae
• (d) Matrix

Q5. Peroxisomes are notable for breaking down which harmful by-product using catalase?

• (a) Lactic acid
• (b) Hydrogen peroxide ($H_2O_2$)
• (c) Ammonia
• (d) Carbon dioxide

Q6. The main structural component of the plant cell wall is:

• (a) Chitin
• (b) Peptidoglycan
• (c) Cellulose
• (d) Keratin

Q7. Light-dependent reactions of photosynthesis occur in the:

• (a) Stroma
• (b) Thylakoid membranes
• (c) Outer chloroplast membrane
• (d) Matrix

Q8. Which cytoskeletal element is the thinnest and made of actin?

• (a) Microtubules
• (b) Intermediate filaments
• (c) Microfilaments
• (d) Centrioles

Q9. The correct order of the endomembrane secretory pathway for a protein is:

• (a) Golgi → Rough ER → vesicle → plasma membrane
• (b) Rough ER → Golgi → vesicle → plasma membrane
• (c) Smooth ER → nucleolus → Golgi → vesicle
• (d) Ribosome → lysosome → Golgi → nucleus

Q10. In a mature plant cell, the large central vacuole primarily maintains:

• (a) ATP production
• (b) Turgor pressure
• (c) DNA replication
• (d) Ribosome assembly

---

Section B — Matching (1 mark each) — 8 marks

Match each organelle (Column X) to its function (Column Y). Write the letter next to the number.

Column X (Organelle)	Column Y (Function)
Q11. Nucleus	A. Digests worn-out organelles via autophagy
Q12. Golgi apparatus	B. Contains genetic material; controls cell activity
Q13. Lysosome	C. Modifies, sorts, and packages proteins
Q14. Mitochondrion	D. Site of aerobic respiration / ATP synthesis
Q15. Rough ER	E. Organizes microtubules; forms spindle in animal cells
Q16. Centrosome	F. Studded with ribosomes; synthesizes secretory proteins
Q17. Chloroplast	G. Site of photosynthesis
Q18. Ribosome	H. Site of protein synthesis (translation)

---

Section C — True/False WITH Justification (2 marks each) — 12 marks

State True or False (1 mark) and give a brief justification (1 mark).

Q19. Ribosomes are membrane-bound organelles found only on the rough ER.

Q20. The nucleolus is a distinct membrane-enclosed compartment inside the nucleus.

Q21. Both mitochondria and chloroplasts contain their own DNA and double membranes.

Q22. Centrioles are typically present in higher plant cells and organize their spindle.

Q23. Smooth ER has ribosomes attached, whereas rough ER does not.

Q24. Intermediate filaments provide mechanical strength and help cells resist tension.

---

[
  {"claim": "Catalase decomposition of hydrogen peroxide is balanced: 2 H2O2 -> 2 H2O + O2 (H and O atoms conserved)", "code": "H_left=2*2; O_left=2*2; H_right=2*2; O_right=2*1+2; result=(H_left==H_right and O_left==O_right)"},
  {"claim": "Cilia/flagella axoneme 9+2 gives 9*2 (doublets) + 2 (central singlets) = 20 microtubules", "code": "total=9*2+2; result=(total==20)"},
  {"claim": "Section A has 10 one-mark, B has 8 one-mark, C has 6 two-mark questions summing to 30 marks", "code": "result=(10*1+8*1+6*2==30)"},
  {"claim": "Microfilament diameter (~7 nm) is smaller than intermediate filament (~10 nm) and microtubule (~25 nm)", "code": "mf=7; imf=10; mt=25; result=(mf<imf<mt)"}
]