Module 6 of 9Lesson 1 of 17 · B01 Plant and animal cells and their parts
BGCSE Science Double Award · Biology · Form 4 · Section 12 Living things
Lesson B01 · about 12 minutes

Plant and animal cells and their parts

Peel the thin skin from inside an onion, add a drop of iodine, and look at it under the school microscope: neat boxes like bricks in a wall. Now scrape the inside of your cheek with a cotton bud and stain it blue: soft, irregular cells. Both are living cells. What do they share, and what makes a plant cell different?

Prof KitsoPaper 4 opens the biology section with a drawing and a magnification almost every year. The marks go to clean single lines, label lines that touch the part, and an answer written like × 2.5.
drawn to look like photomicrographsonion epidermisiodine stain cheek cellsmethylene blue stain
Papers 1, 3 and 4Cells in 3 theory papers (2012–2017)Magnification in 10 of 11 practical papers (2010–2020)🔬 Cell explorer

Learn5 cards

Parts of an animal cell

A cheek cell is a typical animal cell. You can see the around the outside, the inside it, and a .

are tiny: with a school light microscope they look like dots at most. are so small that they are seen only with an electron microscope.

cytoplasmmitochondrioncell membrane nucleusribosomes
Diagram, not to scale. Ribosomes are seen only with an electron microscope.

Parts of a plant cell

A plant cell also has a cell membrane, cytoplasm and a nucleus. Outside the membrane is a . In the middle is a large full of cell sap.

Green cells have , which contain green . Onion epidermis cells are not green: they have no chloroplasts.

cell wallcell membranechloroplast sap vacuolecytoplasmnucleus
A leaf palisade cell. Plant cells have mitochondria too (not drawn).

What the parts do

Nucleus: controls all the activities of the cell; its chromosomes carry the genetic information.

Mitochondrion: aerobic respiration releases energy here. Ribosome: makes proteins.

Cell membrane: controls what enters and leaves the cell; it is . Cell wall: made of cellulose; gives support and keeps the shape; fully permeable.

nucleuscontrols all the activities of the cellmitochondrionrespiration: releases energyribosomemakes proteinscell membranecontrols what enters and leavescell wallsupport; keeps the cell’s shape
Learn the nucleus answer word for word.

Plant cell or animal cell?

Both have a cell membrane, cytoplasm, a nucleus, mitochondria and ribosomes.

Only plant cells have a cell wall, a large sap vacuole and (in green parts) chloroplasts. Plant cells are usually regular and box-shaped; animal cells have no fixed shape.

Compare both sides: “the plant cell has a cell wall but the animal cell does not”.

plantanimalcell walllarge sap vacuolechloroplasts*cell membranecytoplasmnucleusmitochondria* only in green parts (not onion)
Three parts are found only in plant cells.

Magnification

To work out the , measure the same, longest dimension on the drawing and on the photograph, in the same unit (mm). Draw the measuring line on both.

Write the answer as × 2.5: a multiplication sign, 1 decimal place, no unit.

To find the real size: actual size=image sizemagnification\text{actual size}=\dfrac{\text{image size}}{\text{magnification}}. Remember 1 mm = 1000 µm.

magnification=length of drawinglength of photograph\begin{aligned}&\text{magnification}\\&=\dfrac{\text{length of drawing}}{\text{length of photograph}}\end{aligned}
photographdrawing 30 mm75 mm same dimension (longest), same unit magnification = × 2.5
75 mm on the drawing, 30 mm on the photograph.

See it live

Look down the virtual microscope at a cheek cell, an onion epidermis cell and a leaf palisade cell. Switch objectives and focus, then tap each part to see its name and function — and check the onion cell for chloroplasts. Then label a diagram (each line must touch its part), build a plant-versus-animal comparison, and do three magnification questions with the on-screen ruler.

Cell explorer: plant and animal cellsMicroscope views of cheek, onion and palisade cells; tap the parts, label a diagram, compare plant and animal, magnification trainer

In the school lab: making fresh preparations
Onion: 1. Peel a thin layer of epidermis from the inside of an onion scale leaf with forceps. 2. Lay it flat in a drop of water on a clean slide. 3. Add one drop of iodine solution. 4. Lower a cover slip at an angle with a mounted needle, so no air bubbles are trapped. 5. Blot extra liquid with filter paper. 6. Find the cells with the ×10 objective, then turn to ×40.
Cheek: 1. Rub the inside of your own cheek gently with a clean cotton bud. 2. Smear it on a slide and add one drop of methylene blue. 3. Add a cover slip as above and view.
Safety: use only your own cheek and a new cotton bud; put used cotton buds and slides straight into disinfectant. Iodine and methylene blue stain skin and clothes — wear a lab coat. Handle cover slips carefully: they break into sharp pieces.

Worked example3 examples

Example 1Grade C
A student draws one onion epidermis cell from a photograph. The photograph cell is 30 mm long; her drawing is 75 mm long. Which drawing earns the marks, and what is the magnification of her drawing?
✓ Good: earns the marks cell wallcytoplasmnucleus large · clean single lines · ruled labellines that touch the part · no arrows ✗ Weak: loses marks nucleus? too small · sketchy double lines · shadingarrow that does not touch the part
drawingLarge, clean single lines, no shading; labels at the side with ruled lines that touch the part.
formulamagnification=length of drawinglength of photograph\text{magnification}=\dfrac{\text{length of drawing}}{\text{length of photograph}}
substitutemagnification=75 mm30 mm\text{magnification}=\dfrac{75\text{ mm}}{30\text{ mm}}
answer× 2.5\times\,2.5
Why no unit?Both lengths are in mm, so the units cancel. Magnification is a number of times bigger: write × 2.5, not “2.5 mm” and not “x 2.5”.
Example 2Grade B
A drawing of a cell is 9.6 cm long. The same cell in the photograph is 32 mm long. Calculate the magnification of the drawing.
same unit9.6 cm=96 mm9.6\text{ cm}=96\text{ mm}
formulamagnification=length of drawinglength of photograph\text{magnification}=\dfrac{\text{length of drawing}}{\text{length of photograph}}
substitutemagnification=9632\text{magnification}=\dfrac{96}{32}
answer× 3.0\times\,3.0
Change units firstDividing 9.6 by 32 gives × 0.3 — the drawing would be smaller than the photograph, which is impossible here. Put both lengths in mm before you divide, and keep 1 decimal place: × 3.0.
Example 3Grade A
A photomicrograph shows a cheek cell at a magnification of × 400. The cell is 22 mm across in the photomicrograph. Calculate the actual width of the cell in µm.
formulaactual size=image sizemagnification\text{actual size}=\dfrac{\text{image size}}{\text{magnification}}
substituteactual size=22 mm400\text{actual size}=\dfrac{22\text{ mm}}{400}
work outactual size=0.055 mm\text{actual size}=0.055\text{ mm}
convert0.055×10000.055\times1000
answer55 μm55\,\mu\text{m}
Is it sensible?Cheek cells are about 50–60 µm across, so 55 µm makes sense. The actual size does have a unit; only the magnification has none.

Misconception busterfrom the BEC examiner reports

Giving one specific job of the nucleus instead of its general function.
Give its general function: the nucleus controls all the activities of the cell.

Examiner report: 0572 Biology 2023 Paper 3, Q1(a)(ii)

Magnification written with a small letter x, to 2 d.p., or with a unit (x 2.5, × 2.53, 2.5 mm).
A multiplication sign, 1 decimal place, no unit: × 2.5.

Examiner report: 2023 Paper 4, Q5(b)(iii)

Measuring the radius, or a different line on the photograph and on the drawing.
Draw the line across the same, longest dimension on both pictures, then measure both.

Examiner report: 2023 Paper 4, Q5(b)(i)

Lengths written in cm, or the unit repeated, when the answer line already says mm.
Measure in the unit printed on the answer line (mm) and do not add your own unit.

Examiner report: 2024 Paper 4, Q5(b)(ii)

Labels with arrows, or a letter written on the drawing with no line.
Use a ruled label line with no arrowhead that touches the part.

Examiner report: 2024 Paper 4, Q5(a)(ii); 2024 Paper 3, Q11(a)(ii)

Prof KitsoBefore you hand in a drawing, check four things: large, clean single lines, no shading, label lines that touch. Before you hand in a magnification: same unit, × sign, 1 decimal place.

Quick check5 questions · Paper 1 style

1Which structure is found in BOTH plant and animal cells?

  1. ✓ Right. Every cell has a cell membrane around its cytoplasm.
  2. ✗ Not this one. Only plant cells have a cellulose cell wall.
  3. ✗ Not this one. Chloroplasts are found only in green plant cells.
  4. ✗ Not this one. A large permanent sap vacuole is a plant-cell feature.

2Which part controls all the activities of the cell?

  1. ✗ Not this one. The mitochondrion is where aerobic respiration releases energy.
  2. ✓ Right. The nucleus controls all the activities of the cell.
  3. ✗ Not this one. The membrane controls what enters and leaves, not everything the cell does.
  4. ✗ Not this one. Ribosomes make proteins.

3A student looks at onion epidermis stained with iodine. Which part will she NOT see?

  1. ✗ Not this one. Onion cells have a clear cell wall: that is why they look like bricks.
  2. ✗ Not this one. The nucleus stains dark with iodine.
  3. ✓ Right. Onion epidermis grows in the dark inside the bulb: it has no chloroplasts.
  4. ✗ Not this one. Cytoplasm is present as a thin layer.

4Which statement about ribosomes is correct?

  1. ✗ Not this one. That is the mitochondrion.
  2. ✗ Not this one. Chlorophyll is inside chloroplasts.
  3. ✗ Not this one. They are far too small; the light microscope cannot show them.
  4. ✓ Right. Ribosomes make proteins and are too small for a light microscope.

5A drawing is 60 mm long; the photograph is 24 mm long. How should the magnification be written?

  1. ✗ Not this one. Examiners want 1 decimal place, not 2.
  2. ✓ Right. 60 divided by 24 is 2.5: × sign, 1 d.p., no unit.
  3. ✗ Not this one. A small letter x and a unit both lose the mark.
  4. ✗ Not this one. This is the photograph divided by the drawing — upside down.

Exam cornerPaper 4 style · 9 marks

Fig. 5.1 is a drawing of a cell from a leaf, made from a photomicrograph.

A B C D
(a)
Name the parts labelled A, B, C and D. [4]
(b)
State the function of part D. [1]
(c)
Name two parts visible in Fig. 5.1 that a cheek cell does not have. [2]
(d)
The length of the cell along its longest side is 40 mm in the photomicrograph and 96 mm in Fig. 5.1. Calculate the magnification of Fig. 5.1. [2]
Model answer

(a)

A cell wall
B chloroplast
C sap vacuole
D nucleus

(b)

It controls all the activities of the cell.

(c)

A cell wall and chloroplasts.

(d)

formulamagnification=length of drawinglength of photograph\text{magnification}=\dfrac{\text{length of drawing}}{\text{length of photograph}}
substitutemagnification=9640\text{magnification}=\dfrac{96}{40}
answer× 2.4\times\,2.4
Marking key — how the examiner awards the marks
Mark pointMark
(a)A cell wallB1
B chloroplastB1
C sap vacuole (accept vacuole)B1
D nucleusB1
(b)controls all the activities of the cellB1
(c)cell wallB1
chloroplasts / large sap vacuoleB1
(d)9640\dfrac{96}{40} (correct substitution)C1
× 2.4 (× sign, 1 d.p., no unit)A1

Total: 9 marks

Examiner tip. For “name two parts” questions, give two different parts — not “cell wall” and “cellulose wall”. In the calculation, write the formula first: the substitution mark is often the one you keep.

Rememberone-page card to download

  • Animal cell: cell membrane, cytoplasm, nucleus, mitochondria, ribosomes.
  • Plant cell: all of those, plus cell wall, large sap vacuole and (in green parts) chloroplasts. Onion epidermis: no chloroplasts.
  • Nucleus: controls all the activities of the cell. Ribosomes: protein synthesis — seen only with an electron microscope.
  • Drawing: large, clean single lines, no shading; ruled label lines that touch the part, no arrows.
  • Magnification: same dimension, same unit; answer × 2.5 (1 d.p., no unit). 1 mm = 1000 µm.

Two formulas

magnification=length of drawinglength of photograph\text{magnification}=\dfrac{\text{length of drawing}}{\text{length of photograph}}answer: × 2.5, no unit
actual size=image sizemagnification\text{actual size}=\dfrac{\text{image size}}{\text{magnification}}answer has a unit (mm or µm)
plant cellanimal cell
has a cell wallno cell wall
large sap vacuoleno large vacuole
chloroplasts in green partsno chloroplasts
regular, box-like shapeno fixed shape
Download this card (PDF)

Science that earnsa skill you can sell

A weekend microscope club

Younger children love seeing things up close. A USB digital microscope plugs into a laptop or phone, so a small group can watch the screen together.

Run a Saturday club for Standard 5–7 pupils: onion skin, leaves, insect wings, salt and sugar crystals. Teach them to draw what they see with clean lines and labels — the skill you have just learned.

Example costs
USB digital microscopeP450
Glass slides and cover slipsP80
Onions, leaves, paper and pencilsP40
Starting costsP570
8 children × 4 Saturdays at P30P960
Profit after the first monthP390

Get written permission from parents, and hold the club somewhere supervised, such as a church hall or with a teacher at a school. Use only unstained specimens: no chemical stains and no cheek-cell slides outside a school lab. Glass slides can cut — let children handle them only with you watching.

Example figures only — check prices, and agree the venue and times with the owner and with parents.

Syllabus checklist Tap when you can do it

← C47 Natural macromolecules: proteins, fats, carbohydrates and hydrolysisNext: B02 Specialised cells, tissues, organs and systems →

Stadira Training Institute · Gaborone, Botswana · BGCSE Science Double Award (0569) Complete Tutor

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