Cell Structure & Function
About Science MCQs
Science is a core subject in almost every competitive examination, including CSS, PMS, PPSC, FPSC, and NTS. It encompasses the study of the physical world and natural phenomena. Whether you are preparing for a general science paper or a specialized entry test, mastering Science MCQs requires a clear understanding of fundamental concepts and the ability to apply them logically.
Topics Covered in This Category
- Biology: Human anatomy, cell biology, genetics, and ecology.
- Chemistry: Chemical reactions, periodic table, organic and inorganic chemistry.
- Physics: Mechanics, electricity, magnetism, optics, and modern physics.
- Everyday Science: Practical applications of science in daily life, famous inventions, and scientific laws.
How to Prepare for Science Exams
Science is not just about memorizing facts; it is about understanding the "why" and "how" behind natural phenomena. Focus on conceptual clarity rather than rote learning. When practicing MCQs, pay special attention to units of measurement, chemical formulas, and scientific terminologies. Reviewing the explanations for wrong answers is the fastest way to improve your score.
All Questions for: Cell Structure & Function
Question 1: Which scientist first observed cells in 1665 using a microscope?
- A Robert Hooke
- B Anton van Leeuwenhoek
- C Robert Brown
- D Matthias Schleiden
Explanation: Robert Hooke observed cork cells in 1665, coining the term 'cell'.
Question 2: The cell theory was proposed by:
- A Schleiden and Schwann
- B Watson and Crick
- C Hooke and Leeuwenhoek
- D Pasteur and Koch
Explanation: Schleiden and Schwann (1838–39) formulated cell theory; Virchow later added 'omnis cellula e cellula'.
Question 3: Which of the following is a key feature distinguishing prokaryotes from eukaryotes?
- A Prokaryotes lack a membrane-bound nucleus
- B Prokaryotes have mitochondria
- C Prokaryotes are always multicellular
- D Prokaryotes have a nuclear envelope
Explanation: Prokaryotes lack a membrane-bound nucleus; eukaryotes have one.
Question 4: Which organelle is known as the 'powerhouse of the cell'?
- A Mitochondria
- B Nucleus
- C Ribosome
- D Golgi apparatus
Explanation: Mitochondria generate ATP through oxidative phosphorylation.
Question 5: The site of protein synthesis in a cell is the:
- A Ribosome
- B Nucleus
- C Lysosome
- D Golgi apparatus
Explanation: Ribosomes synthesize proteins from amino acids using mRNA as template.
Question 6: The nucleus contains which genetic material?
- A DNA
- B Only RNA
- C Proteins only
- D Lipids
Explanation: The nucleus houses the cell's DNA, which contains the genetic code.
Question 7: Which organelle is responsible for packaging and modifying proteins?
- A Golgi apparatus
- B Lysosome
- C Ribosome
- D Mitochondria
Explanation: The Golgi apparatus modifies, sorts, and packages proteins from the ER.
Question 8: Lysosomes are known as:
- A Suicide bags
- B Powerhouses
- C Protein factories
- D Lipid factories
Explanation: Lysosomes contain digestive enzymes and are the cell's 'suicide bags' or garbage disposal system.
Question 9: The rough endoplasmic reticulum differs from smooth ER by:
- A Having ribosomes attached
- B Having no membrane
- C Being found only in prokaryotes
- D Producing ATP
Explanation: Rough ER has ribosomes attached for protein synthesis; smooth ER lacks ribosomes and is involved in lipid synthesis.
Question 10: Chloroplasts are found in:
- A Plant cells and some algae
- B Animal cells only
- C Bacterial cells only
- D Fungal cells only
Explanation: Chloroplasts occur in plant cells and some algae — not in animal cells.
Question 11: Chloroplasts are the site of:
- A Photosynthesis
- B Cellular respiration
- C Protein synthesis
- D Lipid breakdown
Explanation: Chloroplasts perform photosynthesis, converting light energy into chemical energy.
Question 12: Which organelle is absent in animal cells?
- A Chloroplasts
- B Mitochondria
- C Ribosomes
- D Golgi apparatus
Explanation: Chloroplasts are absent in animal cells; mitochondria are present in both.
Question 13: The cell wall of plant cells is primarily made of:
- A Cellulose
- B Chitin
- C Peptidoglycan
- D Phospholipid
Explanation: Plant cell walls are composed mainly of cellulose.
Question 14: The cell wall of bacteria is primarily made of:
- A Peptidoglycan
- B Cellulose
- C Chitin
- D Lignin
Explanation: Bacterial cell walls are made of peptidoglycan (murein).
Question 15: Fungal cell walls are mainly composed of:
- A Chitin
- B Cellulose
- C Peptidoglycan
- D Lignin
Explanation: Fungal cell walls contain chitin, distinguishing them from plants.
Question 16: The cytoskeleton is made up of which three main components?
- A Microfilaments, intermediate filaments, and microtubules
- B Nucleic acids, lipids, and proteins
- C Ribosomes, lysosomes, and vacuoles
- D Cellulose, chitin, and peptidoglycan
Explanation: The cytoskeleton consists of microfilaments, intermediate filaments, and microtubules.
Question 17: Which of the following is NOT membrane-bound?
- A Ribosome
- B Mitochondria
- C Nucleus
- D Golgi apparatus
Explanation: Ribosomes are non-membrane-bound organelles found free or attached to ER.
Question 18: The nucleolus is the site of:
- A rRNA synthesis and ribosome assembly
- B DNA replication
- C ATP production
- D Lipid synthesis
Explanation: The nucleolus is where ribosomal RNA (rRNA) is synthesized and ribosome assembly begins.
Question 19: Peroxisomes function primarily to:
- A Break down fatty acids and detoxify
- B Synthesize proteins
- C Produce ATP
- D Store water
Explanation: Peroxisomes break down fatty acids and detoxify hydrogen peroxide.
Question 20: The central vacuole is found predominantly in:
- A Plant cells
- B Animal cells
- C Bacterial cells
- D Fungal cells only
Explanation: Plant cells have large central vacuoles for storage, turgor, and waste management.
Question 21: Which organelle modifies proteins with carbohydrate chains?
- A Golgi apparatus
- B Nucleus
- C Ribosome
- D Mitochondria
Explanation: The Golgi apparatus performs glycosylation — adding carbohydrate chains to proteins.
Question 22: The fluid mosaic model describes:
- A The structure of the cell membrane
- B The structure of DNA
- C The structure of ribosomes
- D The structure of chloroplasts
Explanation: The fluid mosaic model (Singer & Nicolson, 1972) describes the cell membrane as a fluid phospholipid bilayer with embedded proteins.
Question 23: Protein synthesis begins in the cytoplasm when:
- A mRNA is translated on ribosomes
- B DNA enters the cytoplasm
- C Ribosomes enter the nucleus
- D The cell divides
Explanation: Translation begins on free ribosomes; proteins destined for secretion move to the ER.
Question 24: Which cellular component is responsible for maintaining cell shape?
- A Cytoskeleton
- B Nucleus
- C Golgi apparatus
- D Lysosome
Explanation: The cytoskeleton provides structural support and maintains cell shape.
Question 25: The endosymbiotic theory explains the origin of:
- A Mitochondria and chloroplasts
- B Nucleus and ribosomes
- C Cell wall and membrane
- D Golgi and ER
Explanation: The endosymbiotic theory proposes that mitochondria and chloroplasts evolved from engulfed prokaryotes.