Cells and Biological Processes
MYP Sciences Framework — Living Systems strand: Cells and Biological Processes (Year 5)
Every question in this unit is really asking the same thing in six different costumes: does a molecule, membrane, or cell have the right shape/gradient/genetic instructions to do its job right now? Enzymes work because their active site shape fits a substrate. Membranes let things through (or don't) because of gradients and pore size. Cells divide accurately because chromosomes get copied and shared with genetic precision. Stem cells become anything because they haven't yet switched off the genes for other tissues. Once you see the shape-and-gradient thread running through it, the graphs and calculations in this chapter stop being separate topics to memorise.
Overview: How This Unit Fits Together
Cells are chemical factories running on catalysts (enzymes), power supplies (respiration/photosynthesis), a copying department (mitosis/meiosis), a delivery network (diffusion/osmosis/active transport), a workforce with fixed job roles (organelles), and a reserve of unassigned staff who can be trained for any job (stem cells). Examiners test whether you can read a graph, do a calculation, or explain a mechanism for each of these — not just recite definitions.
- Enzymes and metabolism sit underneath everything else — respiration and photosynthesis are both just controlled sequences of enzyme-catalysed reactions.
- Cell division (mitosis/meiosis) explains growth, repair, and how genetic variation is generated for reproduction.
- Energy transfer (respiration/photosynthesis) links directly to cell structure — you can't explain a mitochondrion or chloroplast without the equation it runs.
- Transport processes (diffusion, osmosis, active transport) explain how substances actually reach the enzymes and organelles that need them.
- Stem cells connect back to mitosis — they divide by mitosis but can also differentiate, which ordinary body cells cannot do.
The shape of the chapter
Command terms this unit tests hardest
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| State / Identify | One fact, name, or value — no explanation needed or wanted. | Criterion A | Extra explanation earns zero extra marks and wastes time; a labelled value from a graph counts as 'stated'. |
| Describe | Give a detailed account with no reasoning — what happens, in what order, by how much. | Criterion A | Must include a trend or direction (e.g. 'activity increases then plateaus'), not just 'it changes'. |
| Explain | Give reasons — the mechanism that causes the described pattern. | Criterion A/D | Needs a causal link word ('because', 'as a result') connecting structure to function or cause to effect. |
| Analyse | Break down data or a mechanism to show relationships between parts. | Criterion C | Must reference specific data values or specific structural features, not a generic mechanism. |
| Compare | Give similarities AND differences between two named things. | Criterion A | A one-sided answer describing only one item loses half the marks even if the content is accurate. |
| Construct | Build a graph, table, or diagram from given data, following convention. | Criterion C | Missing axis labels, units, or a suitable scale costs marks even if points are plotted correctly. |
Key point
Overview