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cell membrane
The membrane regulates movement; the plant wall provides support.
Class 7 · English Medium · Pearson Edexcel · General science
Pearson iLowerSecondary Science sample overview · Chapter companion part
Year 7 · Cells and microscopes
Explore cell structures, explain their jobs, and judge what a school light microscope can actually show.
Selected Pearson Year 7 biology companion, mapped to the public sample overview. It is placed in the Class 7 Edexcel pathway for access; confirm your school programme year with a teacher. This does not establish equivalence with a national school class or complete programme coverage.
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Learn the idea
A cell is a small living unit. A typical animal cell has a cell membrane around cytoplasm, a nucleus containing genetic information, and mitochondria. A diagram selects features and enlarges them; its colours and proportions are not observations. Specialised cells can differ from this typical model.
Plant cells: shared and different
Typical plant cells share a membrane, cytoplasm, nucleus and mitochondria with animal cells. Many plant cells also have a cellulose cell wall and a large permanent vacuole containing cell sap. Photosynthetic cells contain chloroplasts. A root cell can be a plant cell without chloroplasts: do not identify every plant cell by that feature alone.
Which structure does which job?
The cell wall supports a plant cell; the membrane controls movement of substances in and out. Many reactions occur in the cytoplasm. The nucleus contains genetic instructions and helps control activities. Chloroplasts absorb light for photosynthesis. Mitochondria are organelles (structures inside a cell) where aerobic respiration uses oxygen to transfer energy for cell activities. A large vacuole helps a plant cell stay firm.
Parts of a light microscope
The eyepiece and objective lenses magnify the image. The stage supports a slide and clips hold it. A light source illuminates the specimen; a diaphragm can adjust light. Focus controls bring an image into view. The coarse control makes larger adjustments; the fine control makes smaller ones. The specimen is the sample on the slide. Use equipment only with a teacher and prepared slides.
A safe viewing sequence
Begin with the lowest-power objective so the field of view is wider and the specimen is easier to locate. Centre it and focus as a teacher demonstrates. At higher power use the appropriate fine adjustment and keep the objective from touching the slide. Never use the Sun as a light source, collect unknown microbes, or make chemical stains for this online activity. Paper images work too.
Magnification and detail
Magnification tells how much larger an image appears: eyepiece power multiplied by objective power gives total magnification. A 10× eyepiece and 4× objective give 40×. Resolution means the ability to distinguish nearby details as separate; enlarging a blurry image does not add detail. A routine school light microscope does not reveal every organelle in a textbook diagram.
Observed features and model features
Plant cell walls and chloroplasts in green tissue may be visible with a suitable light microscope. A nucleus can require suitable preparation or stain; do not promise it will always be obvious. A cell membrane pressed against a plant cell wall can be hard to distinguish separately. Mitochondrial detail is not normally resolved clearly in routine school observations. Record only what the supplied image supports.
Read unfamiliar cells carefully
In a supplied model, a firm outer wall, an inner membrane and a large vacuole support a plant-cell identification even if no chloroplasts are drawn. Use several features together. Label a drawing with clear lines and state whether it is a supplied schematic or an actual observation. A missing label in an incomplete picture does not prove the structure is absent.
Worked example
A prepared green-leaf model shows a wall, membrane, large vacuole and chloroplasts. These support a plant-cell identification. With a 10× eyepiece and 40× objective, total magnification is 10 × 40 = 400×. The model supplies features; the calculation alone does not prove those features could be resolved.
- Identify the structure or process before naming its function.
- Use the supplied evidence and explain the link; a label alone is not an explanation.
- Compare your response with the model, then improve one part of your reasoning.
Common mistake
A green rectangle is not automatically a plant cell, and not every plant cell is green. Identify named structures, then state how much the image really shows.
A second magnification example
An eyepiece of 5× and objective of 20× give 100× total. Multiplication finds image enlargement, not the number of structures visible.
A model with missing information
If a supplied diagram omits mitochondria, you cannot conclude the living cell has none. Check whether it is a simplified model and whether other evidence is supplied.
Your written practice
Show your working on paper and enter your answer here. If it does not match, compare the model and try again.
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cytoplasm
Cytoplasm is the cell material where many reactions take place.
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nucleus
The nucleus contains most of the cell’s genetic information and helps control cell activities.
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mitochondria
Mitochondria transfer energy through aerobic respiration; they do not create energy.
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cell wall
The cellulose wall lies outside the membrane.
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chloroplasts
Chloroplasts contain light-absorbing pigments.
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vacuole
The large vacuole helps maintain firmness.
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stage
The stage supports the slide while clips keep it in place.
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400
10 × 40 = 400, so the image is magnified 400 times.
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40
10 × 4 = 40; start with this lower power to find the specimen.
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10
100 ÷ 10 = 10, so the objective is 10×.
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resolution
Resolution concerns separate detail, rather than image size.
Write in your own words. A guardian or teacher should review this response.
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Both have a membrane, cytoplasm, nucleus and mitochondria. The plant model also has a wall, large vacuole and chloroplasts.
Check shared features and plant additions; do not say every plant cell has chloroplasts.
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Root cells often do not photosynthesise, so they need not have chloroplasts. The wall and vacuole support the plant-cell model.
Use more than one feature and connect chloroplasts to photosynthesis.
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Enlargement increases image size but cannot separate details the microscope did not resolve.
Distinguish magnification from resolution in your own words.
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With a teacher, start on low power, locate and centre the specimen, focus correctly, then use fine adjustment when increasing power without touching the slide.
Include teacher supervision, low power and protection of the slide; paper images are an alternative.
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Some structures are not clear at routine school resolution or need special preparation. Record only supported observations and label a model as a model.
Separate what is observed from what a teaching model includes.
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No. The image needs context and clear preparation or labels; a dark mark alone could have another cause.
Look for evidence and state the limit, rather than guessing with certainty.
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The wall supports and strengthens the cell. The membrane controls movement of substances; the wall does not replace it.
Name both structures and connect each to its own function.
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Chloroplasts absorb light for photosynthesis; mitochondria carry out aerobic respiration, transferring energy for cell activities.
Plants photosynthesise in suitable light and also respire; the processes are different.
Science notebook challenge
Make a labelled plant/animal cell comparison and a paper microscope guide. Mark which details are model features and which a supplied photograph actually supports.
Review with a guardian or teacher
- Include all seven named cell structures and correct functions where applicable.
- Multiply lens powers correctly and distinguish enlargement from resolved detail.
- State a safe prepared-slide or paper-only method, without inventing an observation.
Keep your work on paper or in a local file. This page does not upload it or automatically grade the project.
Curriculum companion and further study
This original Kidemy practice is mapped to selected Year 7 objectives in the Pearson iLowerSecondary Science sample overview, PDF page 2. This public source does not establish the full programme or a complete textbook chapter list.
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