Biology · Cell: The Unit of Life · NEET
Ribosomes are NON-membrane bound. NCERT says clearly they are 'not surrounded by any membrane.' A ribosome is just rRNA plus protein packed together as a granule. There is no lipid membrane around it. This is a very common NEET trick, so remember: ribosome = NO membrane.
The main non-membrane bound structures in NEET are: ribosomes, centrioles (and the centrosome), the nucleolus, and cytoskeleton parts like microtubules and microfilaments. Ribosomes and centrioles are the two most asked. All other big organelles (mitochondria, ER, Golgi, lysosome, plastids, nucleus, vacuole) DO have a membrane.
No. A centriole has NO membrane. It is made of nine groups of microtubules arranged in a cartwheel pattern (called 9+0, because there is nothing in the centre). Two centrioles together form the centrosome. They help make the spindle fibres during cell division. Centrioles are found in animal cells but usually not in plant cells.
Yes. Ribosomes are the ONE organelle present in both prokaryotes and eukaryotes. In prokaryotes they are 70S; in eukaryotes they are 80S (but mitochondria and chloroplasts also carry 70S). This is why NEET 2026 asked: 'non-membrane bound organelle found in both' - the answer is ribosomes, not lysosome or mitochondria (those are eukaryote-only and membrane bound).
Membrane bound organelles are wrapped in one or two lipid membranes - like mitochondria (double), lysosome (single), Golgi, ER. This gives them a separate inside space. Non-membrane bound organelles (ribosome, centriole, nucleolus) have no such wrapper; they sit directly in the cytoplasm or nucleoplasm. Prokaryotes lack ALL membrane bound organelles but still have ribosomes.
Because a ribosome is not a compartment - it is a working machine made only of rRNA and protein. It does not need to hold fluid or keep enzymes separate. It grabs mRNA and makes protein out in the open cytoplasm or on the rough ER surface. That is why NCERT lists it as non-membrane bound.
No. The nucleolus sits inside the nucleus but has NO membrane of its own; it is continuous with the nucleoplasm. It is the site of rRNA synthesis. So even though it is inside the membrane-bound nucleus, the nucleolus itself is a non-membrane bound structure. NEET has tested this.
Non-membrane bound cell organelles found in both prokaryotic and eukaryotic cells are ______.
Microtubules are the constituents of:
Many ribosomes may associate with a single mRNA to form multiple copies of a polypeptide simultaneously. Such strings of ribosomes are termed as
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Ribosomes and centrioles. Add the nucleolus and cytoskeleton (microtubules, microfilaments) if the question asks for more non-membrane structures.
No. A centrosome is an organelle made of TWO centrioles lying together. Each centriole shows the 9+0 cartwheel pattern of microtubules. Both are non-membrane bound.
No. Prokaryotes have ribosomes (70S) but no centrioles, no nucleus, and no other membrane bound organelles.
80S eukaryotic ribosome = 60S + 40S. 70S prokaryotic ribosome = 50S + 30S. S stands for Svedberg unit (a measure of sedimentation, not simple size, which is why the numbers do not add up simply).
Neither. Both chromatin and the nucleolus lie inside the nucleus but have no membrane of their own. The nucleolus is where rRNA is made.
