Question
Which of the following statements correctly distinguishes prokaryotic cells from eukaryotic cells?
(A) Prokaryotic cells have 80S ribosomes; eukaryotic cells have 70S ribosomes (B) Prokaryotic cells lack a membrane-bound nucleus; eukaryotic cells have a well-defined nucleus (C) Prokaryotic cells are larger in size than eukaryotic cells (D) Prokaryotic cells have mitochondria; eukaryotic cells do not
Answer: (B)
This exact type of statement-based question appeared in NEET 2024 and is a guaranteed 4-mark pickup if you have the comparison table memorized.
Solution — Step by Step
Option (A) has the ribosomes swapped — prokaryotes have 70S and eukaryotes have 80S. This is one of the most common “trick” options setters use, so flag it immediately.
Prokaryotic cells are actually smaller — typically 1–10 µm, while eukaryotic cells range from 10–100 µm. Option (C) is the direct opposite of the truth.
Mitochondria are found in eukaryotic cells, not prokaryotic ones. The endosymbiotic theory even proposes that mitochondria evolved from ancient prokaryotes — so prokaryotes are the ancestors, not the owners. Option (D) is completely reversed.
The defining feature of a prokaryote is the absence of a membrane-bound nucleus — the DNA floats free in the nucleoid region. Eukaryotes have a nucleus enclosed by the nuclear envelope. Option (B) is the correct and complete distinction.
Why This Works
The word “prokaryote” literally means before nucleus (pro = before, karyon = nucleus). So the membrane-bound nucleus is the defining criterion — everything else (size, organelles, ribosome type) follows from this fundamental structural difference.
Eukaryotes evolved compartmentalization. Having membrane-bound organelles — nucleus, mitochondria, ER, Golgi — lets the cell run parallel processes without interference. Prokaryotes run everything in one open cytoplasmic compartment, which is why they’re faster to divide but simpler in function.
For NEET, always anchor your answer to the nucleus criterion first. If a question asks for the primary distinction, it’s always the membrane-bound nucleus. Other features like ribosomes or cell wall composition are secondary differentiators.
Alternative Method — The Comparison Table Approach
For one-mark MCQs, we don’t always need to reason from first principles. Memorize this table cold:
| Feature | Prokaryote | Eukaryote |
|---|---|---|
| Nucleus | Absent (nucleoid only) | Present, membrane-bound |
| Size | 1–10 µm | 10–100 µm |
| Ribosomes | 70S (50S + 30S) | 80S (60S + 40S) |
| Mitochondria | Absent | Present |
| Cell wall | Present (peptidoglycan in bacteria) | Present in plants/fungi; absent in animals |
| DNA | Circular, no histones | Linear, with histones |
| Examples | Bacteria, Archaea, Cyanobacteria | Plants, Animals, Fungi, Protists |
In a 3-hour NEET paper, you should spend under 30 seconds on this question. The table makes that possible.
The 70S vs 80S distinction has a direct clinical application — many antibiotics (like streptomycin, tetracycline) specifically target 70S ribosomes. This is why they kill bacteria without harming our eukaryotic cells. NEET occasionally tests this application angle.
Common Mistake
Mixing up ribosome sizes is the single biggest error on this topic. Students write “prokaryotes = 80S” after getting confused by the larger number. Here’s the memory trick: 70S = 7 letters in “prokar” — count them: p-r-o-k-a-r-y = 7. Prokaryote → 70S. Lock this in and you’ll never swap them again.
Also watch out for the mitochondria trap. Prokaryotes (specifically bacteria like Paracoccus) are similar to mitochondria evolutionarily — but they do not have mitochondria. Students who know the endosymbiotic theory sometimes confuse similarity with possession.
NEET PYQ Pattern: Prokaryote vs eukaryote comparisons appear almost every year, often as statement-based questions (which statement is correct/incorrect). NEET 2024, 2022, and 2019 all had at least one direct question from this comparison. High weightage, low difficulty — treat this as a guaranteed full-marks topic.