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Playbook

Cell Biology

44 q · 2% HARD. Cell Organelles + Functions (17 q · ribosome/mitochondria/golgi/ER — chapter's biggest subtopic), Cell Structure Fundamentals (6), Prokaryote vs Eukaryote (5), plus osmosis/membrane/respiration. The Osmosis and Tonicity subtopic (4 q · 25% HARD) is the chapter's lone Apply pocket — drill it separately.

questions in the bank
44
tagged HARD
2%
subtopic(s)
8
worked examples
2

When you’ll see it

A cell-organelle function match (ribosome/mitochondria/golgi/ER), a prokaryote-vs-eukaryote distinction, an osmosis-direction prediction, a cell-membrane property question, or a cell-respiration energetics question.

How this chapter is tested

44 q in 10 years, 1 HARD. The chapter that defines 'cell theory' (Schleiden + Schwann, 1839 — all living things made of cells; Virchow, 1855 — cells from pre-existing cells). Cell Organelles + Functions is the giant subtopic (17 q): ribosome (protein synthesis, NO membrane), mitochondria (ATP, 'powerhouse', has its own DNA), chloroplast (photosynthesis, only plants + some protists), rough ER (ribosome-studded, protein modification), smooth ER (lipid synthesis), golgi apparatus (packaging + secretion), lysosomes (digestion, 'suicide bags'), vacuole (storage, large in plants).

Prokaryote vs Eukaryote (5 q) is the rule subtopic. Prokaryotes (bacteria, archaea): NO membrane-bound organelles, NO true nucleus (nucleoid), 70S ribosomes, circular DNA, smaller (1–10 μm). Eukaryotes (plants, animals, fungi, protists): membrane-bound organelles, true nucleus, 80S ribosomes, linear DNA, larger (10–100 μm). All cells have ribosomes + plasma membrane + cytoplasm + DNA. NOT all cells have cell wall (only plants, fungi, bacteria) or true nucleus (prokaryotes don't).

Osmosis and Tonicity (4 q, 25% HARD) is the chapter's lone trap pocket. Water moves from HIGH water potential (low solute) to LOW water potential (high solute). RBC in hypotonic solution → swells + bursts (haemolysis). RBC in hypertonic → shrinks (crenation). The HARD 2021 PYQ asks about RBCs in 2% detergent solution — detergent disrupts membrane lipids INDEPENDENTLY of tonicity, so the cell bursts via membrane disruption (not osmosis). Read the question carefully — same chemistry-of-tonicity trap as Chemistry's 'is this an osmosis question or a membrane-chemistry question'.

The sub-skills

The rules and habits that decide whether you get a question right.

  • Cell organelle function match

    Ribosome → protein synthesis (no membrane). Mitochondria → ATP via cellular respiration (own DNA, double membrane). Chloroplast → photosynthesis (plant only, own DNA). Rough ER → protein modification (ribosome-studded). Smooth ER → lipid synthesis + detoxification. Golgi → packaging + secretion. Lysosome → intracellular digestion. Vacuole → storage. Centrosome → microtubule organisation (animal only).

  • Prokaryote vs eukaryote distinction

    Prokaryote: NO true nucleus, NO membrane-bound organelles, 70S ribosomes, circular DNA. Eukaryote: true nucleus, membrane-bound organelles, 80S ribosomes, linear DNA. ALL cells have plasma membrane + cytoplasm + ribosomes + DNA. NOT all have cell wall or membrane-bound nucleus.

  • Osmosis-direction prediction

    Water moves from high water potential (low solute conc) to LOW water potential (high solute conc). Cell in hypotonic solution (lower outside conc) → water in → swells/bursts. Cell in hypertonic (higher outside conc) → water out → shrinks. Isotonic → no net movement.

  • Cellular respiration energetics

    Glycolysis (cytoplasm, anaerobic) → glucose to 2 pyruvate + 2 ATP. Krebs cycle (mitochondrial matrix) → pyruvate to CO₂ + NADH + FADH₂ + 2 ATP. ETC (inner mitochondrial membrane) → NADH/FADH₂ to ATP via O₂. Total = 36–38 ATP per glucose. Anaerobic = 2 ATP only.

2 worked examples from the bank

Real past-year questions illustrating the playbook. Click to reveal options + solution.

Example 1Cell BiologyHARD
If human blood is placed in a 2% detergent solution, what will happen to the RBC ?

[Q96 · Apr · 2021]

Example 2Cell BiologyMODERATE
Consider the following statements: I. All cells possess cell wall. II. All cells have ribosomes present inside. III. All cells have well-organized nucleus. IV. All cells have linear DNA molecules present in them. Which are correct?

[Q95 · Apr · 2026]

Traps to expect

Distractor shapes specific to this chapter. The page-wide Traps section covers the bank-level patterns.

  • Cell wall in animal cells

    Animal cells have NO cell wall — only plasma membrane. Plants, fungi (chitin), bacteria (peptidoglycan), and some protists have cell walls. Distractor says 'all cells have a cell wall'. Statement-evaluation trap — common in multi-statement questions.

  • Nucleus in all cells

    Prokaryotes have NO true nucleus (just a nucleoid region with DNA). Mammalian RBCs LOSE their nucleus during maturation. Distractor says 'all cells have a well-organised nucleus' — false on two counts.

  • Osmosis-vs-membrane-disruption confusion

    When the external solution disrupts cell membranes chemically (detergents, alcohols, hypotonic saponins), the cell bursts via MEMBRANE DISRUPTION, not osmosis. Distractor says 'cell bursts because hypotonic' when the actual mechanism is detergent dissolving the lipid bilayer. Read for solvent identity.

Drill every cell biology question

44 questions from the bank, scoped to 8 bundled subtopics.

Drill the 44 questions

Related playbooks

Often paired with this one — drill these next if you found the worked examples above tractable.