Covers NCERT Class 11 Biology, Chapter "Cell: The Unit of Life" — cell theory, prokaryotic vs eukaryotic organisation, and every membrane-bound organelle NEET tests on. Foundational for genetics, physiology and molecular biology chapters that follow.
Fluid mosaic model of the plasma membrane, prokaryotic vs eukaryotic cell comparison table, semi-autonomous organelles (mitochondria & plastids — their own DNA, 70S ribosomes), Golgi apparatus and the endomembrane system's roles, lysosome function ("suicide bags"), and 70S vs 80S ribosome distribution across cell types and organelles.
Cell theory (Schleiden & Schwann, extended by Virchow): all living organisms are composed of cells; the cell is the basic unit of structure; new cells arise only from pre-existing cells ("Omnis cellula-e cellula").
Prokaryotic cells lack a membrane-bound nucleus and most membrane-bound organelles; their genetic material lies free in the cytoplasm as a nucleoid. Ribosomes are 70S. Mesosomes (in some bacteria) aid respiration, cell wall formation, and DNA replication support.
Plasma membrane: the Singer–Nicolson fluid mosaic model describes a phospholipid bilayer with proteins that can move laterally ("fluid") and are unevenly distributed ("mosaic") — integral proteins span the membrane, peripheral proteins sit on one surface.
Endoplasmic reticulum: Rough ER (ribosome-studded) is the site of protein synthesis and is continuous with the nuclear envelope; Smooth ER synthesises lipids and, in liver cells, detoxifies drugs and poisons.
Golgi apparatus: cis face (receiving, near ER) and trans face (releasing, towards plasma membrane) — packages, modifies and dispatches materials; also the primary site of glycosylation and lysosome formation.
Lysosomes are membrane-bound sacs of hydrolytic enzymes formed by the Golgi, active at acidic pH — called "suicide bags" because their rupture can digest the cell's own contents (autolysis).
Mitochondria and plastids are semi-autonomous: they contain their own circular DNA and 70S ribosomes (like bacteria), and can divide independently of the cell cycle — strong evidence for the endosymbiotic theory.
Ribosomes: 70S (= 50S + 30S) in prokaryotes, mitochondria and chloroplasts; 80S (= 60S + 40S) on the rough ER and free in the cytoplasm of eukaryotic cells. S = Svedberg unit, a sedimentation coefficient — not simply additive, which is why 50S+30S = 70S, not 80S.
The nucleus (Robert Brown, 1831) is bound by a double membrane, the nuclear envelope, perforated by nuclear pores that regulate macromolecule traffic between nucleus and cytoplasm; it houses chromatin and one or more nucleoli (site of rRNA synthesis and ribosome assembly).
The exact numbers NEET tends to ask directly — memorise these as hard facts, not just concepts.
Original questions modelled on recurring NEET question types — not verbatim reproductions of any official paper.
Scaled from direct NCERT recall (Q1–Q6) to mixed NEET-level difficulty (Q7–Q15).
Purely a recall device — not a reinterpretation of the source stories.
Picture the cell as a small, self-sufficient city. The nucleus is the Rajmahal — the palace at the centre, holding the royal decree (DNA) that governs everything the city does. Mitochondria are Agni's chambers, the fire-temples that turn raw fuel into usable energy for the whole city — "powerhouse" is not just a textbook phrase, it is Agni's actual role. Ribosomes, especially those lining the rough ER, are Vishwakarma's workshops, building the city's tools and materials (proteins) piece by piece. The Golgi apparatus is Kubera's treasury and dispatch house — nothing leaves the city without being packaged, labelled and sent out through his warehouse. And the lysosomes are Yamraj's chambers: quiet, contained, but able to dissolve anything — including the city itself — the instant their doors are forced open, which is exactly why the "suicide bag" description sticks.
"Seventy stays with the simple folk" — 70S ribosomes belong to prokaryotes and the two organelles that behave like leftover prokaryotes (mitochondria, chloroplast). Everything else in a eukaryotic cell's cytoplasm runs on 80S.