MYP Biology: Microscopes & Studying Cells FAQ

This topic is assessed across MYP Biology's four criteria: Criterion A tests your knowledge of cell structure, organelles and cell theory; Criterion B and C assess your practical skills, including calculating magnification and processing measurement data; Criterion D asks you to reflect on how microscopy has advanced medicine.

Magnification is how much bigger an image appears compared to the real object; resolution is the ability to distinguish two close points as separate. A microscope can magnify an image enormously, but if resolution is poor, the image just gets bigger and blurrier — not clearer.

Total magnification equals eyepiece lens power multiplied by objective lens power. So a 10x eyepiece with a 40x objective gives 400x magnification. Always state the units next to your measurements and show the multiplication step — examiners award marks for method, not just the final number.

A light microscope uses visible light and glass lenses, magnifies up to about 1,500x, and lets you view living cells; an electron microscope uses a beam of electrons, magnifies over 500,000x, but needs a vacuum, so specimens must be dead and specially prepared.

Actual size equals the size of your drawing divided by the magnification you used. Measure the drawing in millimetres, convert to micrometres by multiplying by 1000, then divide by the magnification stated on your diagram to get the real cell size in micrometres.

A wet mount needs five careful steps: place the specimen on a slide, add a drop of water or stain, lower the coverslip at an angle to avoid air bubbles, then focus on low power before moving to high power. Skipping the angled coverslip step is the most common mistake I see.

Most cells are almost transparent, so a stain like iodine or methylene blue adds contrast, making organelles like the nucleus and cell wall visible against the background. Without staining, you'd see an outline but little internal detail — which is why plant cell labs almost always ask you to stain first.

Magnification and scale calculations are usually marked under Criterion C: Processing and Evaluating, since you're interpreting data and showing calculation steps. Criterion A covers the underlying theory, like organelle function, while Criterion D might ask you to evaluate the impact of microscopy on diagnosing disease.

Yes — under Criterion A you're expected to know the function of key organelles: nucleus, mitochondria, chloroplast, ribosomes, and cell membrane, and to compare plant and animal cells. Command terms like 'state' and 'outline' mean examiners want concise, accurate recall, not lengthy explanations.

The most common mistake is drawing cartoon-style cells instead of biological drawings: no shading, a single continuous line, a title, the magnification stated, and labels with ruled lines touching the structure. I mark dozens of these each term, and missing the magnification statement alone can cost a full mark.

Cells isn't conceptually difficult, but it's mark-heavy on technique: getting magnification calculations, scale bars and biological drawing conventions right takes practice, not just understanding. Most students who struggle here haven't lost the biology — they've lost marks on the maths and drawing rules around it.

The skills your child builds now — magnification calculations, biological drawing, staining technique — reappear directly in DP Biology's cell structure topic and often resurface in the internal assessment, where students design their own microscopy-based investigation. According to the IB, the current Biology guide, first examined in 2025, still opens with cell theory as its foundational topic.

Look for resources with worked magnification calculations, biological drawing checklists, and past-paper-style questions, not just diagrams to label. The best materials pair each skill with a mark-scheme, so your child can see exactly why marks are lost or gained on cell topic assessments.