Three cell types, one shared core
All three cell types share a cell membrane, cytoplasm and ribosomes. Plant and animal cells add a nucleus and mitochondria. Plant cells alone add three more — Wall (cellulose), Chloroplasts (in green parts only) and a large permanent Vacuole of cell sap: remember WCV for the plant extras. Bacteria have a wall too, but it is not made of cellulose.
One structure, one verb
Nucleus — contains the genetic material (DNA), controls cell activities. Cytoplasm — where the chemical reactions happen. Cell membrane — controls what enters and leaves (selectively permeable). Cell wall — supports the cell and keeps its shape (fully permeable). Chloroplast — site of photosynthesis. Mitochondrion — site of aerobic respiration, releasing energy for cell activities. Ribosome — site of protein synthesis. Vacuole — holds cell sap and keeps the plant cell turgid.
Specialised cells: shape follows the job
Ciliated cells beat their cilia to move mucus along the trachea and bronchi (many mitochondria supply the energy). Root hair cells have a long extension giving a large absorbing surface, and no chloroplasts. Palisade mesophyll cells are tall columns packed with chloroplasts near the top of the leaf, for photosynthesis. Neurones have a long axon that conducts electrical impulses, with dendrites collecting signals. Red blood cells are biconcave with no nucleus, leaving room for haemoglobin, to transport oxygen. Sperm (tail, acrosome enzymes, many mitochondria) and egg cells (large, with a food store) carry out reproduction.
Drawn from real examiner reports.
Animal cells DO have mitochondria
In tick-and-cross tables candidates cross mitochondria for animal cells and tick chloroplasts — the two look alike as small oval organelles, but only chloroplasts are plant-only. Animal cells respire, so they need mitochondria. Say that mitochondria release energy from glucose, never that they "make" or "produce" energy.
Cell wall ≠ cell membrane
The wall supports the cell and keeps its shape; it is made of cellulose and is fully permeable, so it selects nothing. The membrane controls the movement of substances into and out of the cell and is selectively permeable. "The cell wall controls what enters" scores zero, and so does "the cell membrane provides support". Every cell has a membrane; only plant and bacterial cells have a wall.
Flagged s22 P42 Q1b · w22 P32 Q2 — candidates gave the wrong structure's function.
Chloroplast ≠ chlorophyll
The chloroplast is the organelle — the site of photosynthesis. Chlorophyll is the green pigment inside it that absorbs the light energy. Examiners penalise "the chlorophyll carries out photosynthesis". Name the organelle when asked where photosynthesis happens; name the pigment only when asked what absorbs the light.
Root hair absorbs; xylem transports
Root hair cells absorb water by osmosis and mineral ions by active transport from the soil — the long, thin hair increases the surface area for this. Xylem vessels then transport that water and the dissolved ions up the plant; they are dead, hollow tubes with lignin-thickened walls. Never write that root hair cells transport water to the leaves.
Flagged s23 P32 Q2c — transport described as the function of root hair cells.
Tissue ≠ organ ≠ organelle
The hierarchy is organelle → cell → tissue → organ → organ system → organism. A tissue is a group of similar cells (palisade mesophyll, spongy mesophyll, vascular tissue, muscle, ciliated epithelium); an organ is a group of different tissues (leaf, heart, kidney). Asked to name a tissue, candidates write "leaf" (an organ), "chloroplast" (an organelle) or "red blood cells" (cells). Step to the level the question names before you answer.
Flagged s22 P12 Q5 · w22 P23 Q6 · s22 P11 Q5 (mesophyll and vascular bundles are tissues, not organs).
Bacterial DNA is not a nucleus
Bacteria are prokaryotic: a single circular chromosome lies free in the cytoplasm, alongside small extra rings of DNA called plasmids that carry additional genes such as antibiotic resistance. Calling that DNA "the nucleus" loses the mark. Bacteria also have no mitochondria and no chloroplasts, so never list those in a bacterial cell answer.
Name the structure, then the verb
For "state the function of X", use [structure] + [action verb] + [what it does]: "the mitochondria are the site of aerobic respiration, releasing energy for cell activities". One mark per distinct correct function. "It helps the cell" scores nothing.
Adaptation = structure → how → function
For "explain how [cell] is adapted for [function]", chain three links: the structure, how it helps, and the function achieved. "Biconcave disc shape → increases the surface area → oxygen diffuses in and out faster." Naming the feature on its own caps you at one mark.
"Compare" means both sides
A comparison mark needs both halves stated: "plant cells have a cell wall; animal cells do not". Writing only "plant cells have a cell wall" is a description, not a comparison, and scores at most one mark.
MCQ trap: right structure, wrong function
Multiple-choice distractors pair a real structure with another structure's function — cell wall = controls entry and exit, chlorophyll = site of photosynthesis, root hair = transports water. Check that both halves of an option match before you choose it.
Cell: the basic structural and functional unit of all living organisms; the smallest unit that can carry out life processes independently.
Tissue: a group of similar cells that work together to perform a specific function (e.g. palisade mesophyll tissue, muscle tissue).
Organ: a group of different tissues that work together to perform a specific function (e.g. leaf, heart, kidney).
Organ system: a group of organs that work together to carry out related functions (e.g. digestive system, circulatory system).
Organism: an individual living thing made up of organ systems (or, in unicellular organisms, a single cell).
State the function of the cell membrane.
State the function of each of the following structures in a plant cell:
(a) Nucleus
(b) Mitochondria
(c) Chloroplasts
