Pair every structure with its function
Statements 2.2-2.3 mark a structure AND its function, so learn each as a pair: nucleus (holds DNA, controls the cell); cytoplasm (site of reactions); cell membrane (controls entry/exit, partially permeable); cell wall (cellulose, supports the cell); mitochondria (respiration, releases energy); chloroplasts (chlorophyll, photosynthesis); ribosomes (protein synthesis); vacuole (cell sap, keeps a plant cell turgid). Naming a structure without its function scores only half.
Cells share five parts; three are plant-only
Both plant and animal cells have a nucleus, cytoplasm, a cell membrane, mitochondria and ribosomes. Only plant cells have the "plant-only three": a cellulose cell wall, chloroplasts and a large permanent vacuole. Animal cells have none of these three (they may have small, temporary vacuoles). In a differences question, list the plant-only three and say the animal cell lacks each. Plant cells also keep a fixed regular shape; animal cells are more rounded.
Magnification links image size and actual size
Magnification M is how many times bigger the image is than the real object: M = image size / actual size. Rearranged, actual size = image / M and image = M × actual. Magnification has no units (it is a ratio), but image and actual sizes MUST be in the same unit before dividing. The commonest conversion is 1 mm = 1000 µm: a 45 mm image of a cell that is really 30 µm wide gives M = 45000 / 30 = 1500, written ×1500. Convert first, divide, then round only as asked.
Drawn from real examiner reports.
Cell wall vs cell membrane
The cell MEMBRANE controls entry and exit because it is partially permeable. The cell WALL does the opposite job: it is freely permeable, and its job is to support and strengthen the cell. Writing "the cell wall controls what goes in and out" is a marked error. The wall is made of cellulose, and only plant cells have one — never give an animal cell a wall.
Releases energy, not makes energy
Mitochondria are the site of aerobic respiration, which RELEASES energy already stored in glucose — energy is never made from nothing. Write "site of respiration / releases energy", not "makes energy" or "produces energy". This precision matters wherever respiration appears: the process transfers energy from glucose, it does not create it.
Mitochondria vs chloroplasts
Do not swap these. Mitochondria carry out aerobic respiration (release energy from glucose) and are in BOTH plant and animal cells. Chloroplasts carry out photosynthesis (capture light energy using chlorophyll) and are ONLY in the green parts of plant cells. Respiration releases energy; photosynthesis captures light energy — different processes in different structures.
Large permanent vacuole is plant-only
A large permanent vacuole filled with cell sap is one of the plant-only three, so its presence marks a cell as a plant cell. Animal cells have only small, temporary vacuoles (or none). Do not draw a big vacuole in an animal cell, and do not draw many small vacuoles in a plant cell — the plant cell has ONE large permanent vacuole.
Convert units before dividing
Image size and actual size are often in different units (mm vs µm). Dividing the numbers as given, without converting, makes an answer of ×1500 come out as ×1.5 — a factor of 1000 wrong. Always convert both to the same unit (1 mm = 1000 µm), then divide image by actual, then round as the question specifies. Show working so a mis-rounded answer still earns method marks.
Vague function loses the mark
Organelle-function marks are lost to loose wording. Say ribosomes are the "site of protein synthesis", not "makes things"; chloroplasts "contain chlorophyll that absorbs light", not just "for photosynthesis". Match the command word: "describe" wants the feature stated; "explain" wants structure linked to function (e.g. many mitochondria release a lot of energy).
Spot a plant cell by the plant-only three
For plant-vs-animal questions use the plant-only three checklist: cellulose cell wall, chloroplasts, large permanent vacuole. If a cell in a diagram has any of these three it is a plant cell; if it has none it is an animal cell. List the three and say the animal cell lacks each.
Magnification: write the formula first
Always write M = image / actual, convert both lengths to a common unit (1 mm = 1000 µm), then substitute. Quote magnification as a ratio with no units. Writing the formula and the substitution banks method marks even if the final number is wrong.
Use a structure-to-function table
Prepare a structure → function table: down the side list nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes, vacuole; across from each write its precise function. For "state the function of X", read straight across for the exact phrase.
Cells are the basic building blocks of living organisms. You need to name each structure (organelle), give its function, and know which structures make a plant cell different from an animal cell.
Structure and function (two-element, mark-scheme form):
| Structure | Function | In which cells? |
|---|---|---|
| Nucleus | Contains the genetic material (chromosomes made of DNA, deoxyribonucleic acid); controls the cell's activities and cell division | Plant and animal |
| Cytoplasm | Jelly-like liquid where most of the cell's chemical reactions take place (many controlled by enzymes) | Plant and animal |
| Cell membrane | Controls what substances enter and leave the cell; it is partially permeable | Plant and animal |
| Cell wall | Made of cellulose; supports and strengthens the cell and keeps its shape; it is freely permeable | Plant only |
| Mitochondria | Site of aerobic respiration, which releases energy from glucose | Plant and animal |
| Chloroplasts | Contain the green pigment chlorophyll, which absorbs light energy for photosynthesis | Plant only (green parts) |
| Ribosomes | Site of protein synthesis (where proteins are made) | Plant and animal |
| Vacuole | A large permanent vacuole filled with cell sap; keeps the cell firm (turgid) and supports it | Plant only (large & permanent) |
Plant vs animal cells (statement 2.4):
Magnification (used in the light-microscope practical):
Magnification is a ratio (no units). Convert image and actual to the same unit first: .
State the function of the nucleus.
State the function of each of the following cell structures: (a) the nucleus, (b) the cell membrane. (2 marks)
