Free Prokaryotic and Eukaryotic Cells MCQs with Answers

1. The main difference between a prokaryotic and a eukaryotic cell is that a prokaryotic cell has

• A. no ribosomes
• B. no membrane bound nucleus or organelles
• C. no genetic material
• D. no plasma membrane

Explanation: Prokaryotes keep their DNA in a nucleoid region with no surrounding envelope and have no mitochondria, endoplasmic reticulum or Golgi apparatus. They do have ribosomes, though the 70S type rather than the 80S type of the eukaryotic cytoplasm, and that difference is exactly what several antibiotics exploit. Every cell has genetic material and a plasma membrane.

2. Ribosomes in the cytoplasm of a bacterium are of which type?

• A. 70S
• B. 80S
• C. 90S
• D. 60S

Explanation: Prokaryotic ribosomes are 70S, made of a 50S and a 30S subunit, while eukaryotic cytoplasmic ribosomes are 80S. Antibiotics such as streptomycin and tetracycline bind the 70S ribosome and leave the host's 80S ribosomes alone, which is why they kill bacteria without killing the patient. Mitochondria and chloroplasts also contain 70S ribosomes, evidence for the endosymbiotic theory.

3. An electron microscope can reveal detail that a light microscope cannot because

• A. it magnifies the specimen many more times
• B. the wavelength of an electron beam is far shorter, giving much greater resolving power
• C. it can be used on living specimens
• D. it uses ultraviolet light instead of visible light

Explanation: Resolution is limited by wavelength, and the very short wavelength of an electron beam allows two points less than a nanometre apart to be seen as separate, against about 200 nanometres for a light microscope. Magnification without resolution simply enlarges a blur, which is the distinction the question is testing. The specimen must be dead and in a vacuum, so living material cannot be examined.

4. The cell wall of a fungus is made mainly of

• A. cellulose
• B. peptidoglycan
• C. chitin
• D. lignin

Explanation: Fungal walls are built from chitin, the same nitrogen containing polysaccharide found in the exoskeleton of insects, which is one reason fungi are placed in their own kingdom rather than with plants. Plant walls are cellulose and bacterial walls are peptidoglycan. Lignin is an additional strengthening material deposited in the walls of woody plant tissue.

5. The cell wall of a bacterium is composed of

• A. peptidoglycan
• B. cellulose
• C. chitin
• D. phospholipid

Explanation: Peptidoglycan, also called murein, is a mesh of sugar chains cross linked by short peptides, and it is unique to bacteria, which is why penicillin can block its synthesis and kill a growing bacterium without harming human cells. The Gram stain works by distinguishing a thick peptidoglycan layer from a thin one. A phospholipid bilayer is a membrane, not a wall.

6. The flagellum of a eukaryotic cell differs from that of a bacterium in that it

• A. is made of the protein flagellin
• B. rotates like a propeller at its base
• C. is shorter and never used for movement
• D. has a 9 plus 2 arrangement of microtubules enclosed by the plasma membrane

Explanation: A eukaryotic flagellum, as in a sperm, is an extension of the cell containing nine outer pairs of microtubules around a central pair, and it beats by the sliding of these microtubules using ATP. A bacterial flagellum is a much simpler solid filament of flagellin outside the cell that rotates like a screw. The two structures are not homologous despite sharing a name.

7. Lysosomes are called 'suicide bags' because

• A. They contain digestive enzymes
• B. They can digest the cell itself when ruptured
• C. They kill bacteria
• D. They produce toxic substances

Explanation: When lysosomes rupture, their hydrolytic enzymes can digest the cell's own components, causing autolysis.

8. Which of the following has its own DNA and 70S ribosomes?

• A. Nucleus
• B. Mitochondria
• C. Golgi apparatus
• D. Peroxisomes

Explanation: Mitochondria (and chloroplasts) have their own circular DNA and 70S ribosomes, supporting the endosymbiotic theory.

9. The site of photosynthesis in eukaryotic cells is

• A. Mitochondria
• B. Chloroplast
• C. Ribosome
• D. Nucleus

Explanation: Chloroplasts contain chlorophyll and are the site of photosynthesis in plant cells and algae.

10. Which of the following statements best compares cell division in prokaryotic and eukaryotic cells?

• A. Eukaryotes divide by budding; prokaryotes by mitosis
• B. Eukaryotes use binary fission; prokaryotes by meiosis
• C. Eukaryotes divide by mitosis; prokaryotes by binary fission
• D. Both use mitosis by cell division

Explanation: Mitosis needs a spindle and organised chromosomes, which only eukaryotes possess, while a prokaryote simply replicates its single circular chromosome and splits by binary fission. This is much faster, which is why bacteria can divide every twenty minutes. Meiosis is confined to eukaryotes producing gametes.