Biology · Cell: The Unit of Life · NEET
No. Prokaryotic cells do NOT have a true (well-defined) nucleus. Their DNA is not covered by a nuclear membrane, so it lies free in the cytoplasm in a region called the nucleoid. Eukaryotic cells DO have a true nucleus with a double nuclear membrane around the DNA. This single point is the most tested difference in NEET.
70S ribosomes are found in prokaryotes; 80S ribosomes are found in the cytoplasm of eukaryotes. 'S' means Svedberg unit (a measure of how fast a particle settles, not just size). A 70S ribosome has 50S + 30S subunits. An 80S ribosome has 60S + 40S subunits. Note: mitochondria and chloroplasts of eukaryotes also contain 70S ribosomes, which is a common NEET trap.
Bacterial (prokaryotic) DNA is naked, double-stranded and circular. 'Naked' means it is NOT wrapped around histone proteins and NOT enclosed by a nuclear membrane. In eukaryotes, the negatively charged DNA is wrapped around a positively charged histone octamer to form a nucleosome. Remember: prokaryote = naked circular DNA; eukaryote = DNA + histones.
Prokaryotes: bacteria, blue-green algae (cyanobacteria like Nostoc, Oscillatoria), mycoplasma and PPLO. Eukaryotes: all protists, plants, animals and fungi. NEET trap: Saccharomyces (yeast) is a fungus, so it is a EUKARYOTE, not a prokaryote — even though it is a microbe.
No. Prokaryotes lack ALL membrane-bound organelles — no mitochondria, no endoplasmic reticulum, no Golgi, no lysosomes, no plastids. Instead, functions like respiration are handled by the mesosome (an infolding of the plasma membrane). The only organelle prokaryotes share with eukaryotes is the ribosome, which is non-membrane bound.
Yes, generally. Prokaryotic cells are usually smaller (about 1–10 micrometre) and multiply faster than eukaryotic cells (about 5–100 micrometre). Mycoplasma is the smallest prokaryote (0.3 micrometre) and the smallest living cell. Do not use size as the DEFINING difference for NEET, though — the true nucleus and membrane-bound organelles are the defining points.
No, cell wall alone cannot separate them. Both bacteria (prokaryotes) and plant/fungal cells (eukaryotes) have cell walls, while animal cells (eukaryotes) do not. So a cell wall is present in some of both groups. The reliable dividing line is the presence of a true nucleus and membrane-bound organelles, which only eukaryotes have.
Which of the following nucleic acids is present in an organism having 70S ribosomes only?
Statement I: In prokaryotes, the positively charged DNA is held with some negatively charged proteins in a region called nucleoid. Statement II: In eukaryotes, the negatively charged DNA is wrapped around the positively charged histone octamer to form nucleosome. Choose the correct answer.
Which among the following is not a prokaryote?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The main difference is the nucleus. Prokaryotes have no true nucleus (DNA is naked in the nucleoid) and no membrane-bound organelles. Eukaryotes have a true nucleus enclosed by a nuclear membrane and many membrane-bound organelles.
Yes. Ribosomes are non-membrane bound and present in both. Prokaryotes have 70S ribosomes; eukaryotes have 80S ribosomes in the cytoplasm but also 70S ribosomes inside their mitochondria and chloroplasts.
No. A virus is neither prokaryote nor eukaryote because it is non-cellular (it has no true cell structure). Prokaryotes are cells with a plasma membrane, cytoplasm and ribosomes; viruses are not cells.
Eukaryotic cells are generally larger (about 5–100 micrometre) than prokaryotic cells (about 1–10 micrometre). Mycoplasma (0.3 micrometre) is the smallest prokaryote and the smallest living cell.
Yes. Prokaryotes have DNA, but it is naked, double-stranded and circular, lying free in the nucleoid without a nuclear membrane and without histone proteins. Many also carry small extra circular DNA called plasmids.
