Every living thing is made of cells. Animal and plant cells share most of their structures, plant cells add a few extras, and bacterial cells are smaller and simpler, with no nucleus at all.
Animal and plant cells both have a cell membrane, cytoplasm, a nucleus, mitochondria and ribosomes. Plant cells also have a cellulose cell wall, a large permanent vacuole and, in parts exposed to light, chloroplasts. A bacterial cell has a cell wall, cell membrane, cytoplasm and ribosomes, but no nucleus: its genetic material is a loop of circular DNA, and it may also carry small rings of DNA called plasmids.
Fig. 1: a plant cell and an animal cell, with the structures each one contains
Section 01
Animal and plant cells compared.
Pick the animal cell in the simulator, turn it, and click each part to read what it does. Then switch to the plant cell and look for the three structures the animal cell does not have.
Structure
Function
Animal
Plant
Bacterium
cell membrane
controls which substances enter and leave the cell
yes
yes
yes
cytoplasm
where most of the chemical reactions of the cell take place
yes
yes
yes
ribosomes
make proteins (protein synthesis)
yes
yes
yes
nucleus
contains the genetic material (DNA in chromosomes) that controls the cell
yes
yes
no
mitochondria
site of most of the reactions of aerobic respiration, releasing energy
yes
yes
no
cell wall
strengthens the cell, keeps its shape, stops it bursting when it takes in water
no
yes (cellulose)
yes (not cellulose)
chloroplasts
contain chlorophyll, which absorbs light energy for photosynthesis
no
yes, in cells exposed to light
no
vacuole
large permanent vacuole holds cell sap and keeps a plant cell firm
small, temporary only
yes, large and permanent
no
Examiner trap
Plant cells have mitochondria as well as chloroplasts. Chloroplasts do not replace mitochondria: plant cells respire all the time, day and night, so a palisade cell contains both. Not every plant cell has chloroplasts either: root cells and onion bulb cells are not exposed to light and have none.
Section 02
Bacteria: no nucleus.
Switch the simulator to the bacterial cell. It is drawn about 20 times larger than it really is compared with the other two: a real bacterium is only about 1 to 5 μm long.
Cell wall: supports the cell and stops it bursting, like a plant cell wall, but it is not made of cellulose.
Cell membrane, cytoplasm and ribosomes: the same jobs as in animal and plant cells. The ribosomes make proteins.
Circular DNA: there is no nucleus. The main genetic material is a single loop of DNA lying free in the cytoplasm.
Plasmids: small extra rings of DNA carrying a few genes, for example a gene for resistance to an antibiotic.
Not present: no nucleus, no mitochondria and no chloroplasts.
Stage 1 · Learn
Check what the sim just showed you
Four quick checks. Each correct answer earns XP and records this skill on your profile.
Quick check+10 XP
Which three structures are found in a plant cell but not in an animal cell?
Quick check+10 XP
Where is the genetic material in a bacterial cell?
Quick check+10 XP
What is the function of the mitochondria?
Quick check+10 XP
Which structure is found in animal, plant and bacterial cells?
Section 03
Spotting structures in diagrams and photographs.
Exam questions show a drawing or a photomicrograph (a photograph taken through a microscope) and ask you to name or label the parts. Practise in the simulator: in Find it, read a function and click the right structure; in Name it, one structure glows and you choose its name.
Cell wall or membrane? In a plant cell the wall is the thick outer line; the membrane is pressed tightly against the inside of it and is usually too thin to see separately in a light micrograph.
Nucleus: the largest, darkest-stained structure, usually round. A plant cell pushes it to the edge, next to the wall, because the vacuole fills the middle.
Chloroplasts: small green oval bodies, often lined up round the edge of a plant cell.
Vacuole: in a plant cell, the large clear central space. It often looks empty in a photograph.
Mitochondria and ribosomes: mitochondria are small rods or ovals; ribosomes are tiny dots, far too small to see clearly with a light microscope.
Examiner trap
A label line must touch the structure you name. A line ending in the vacuole but labelled cytoplasm, or ending on the thick outer line of a plant cell but labelled cell membrane, scores no mark.
Stage 2 · Exam
Exam-style questions
Unlocks once the four checks above are done. Worth more XP, written to IGCSE Paper 2 and Paper 4 standard.
Finish the four checks above to unlock the exam questions
Exam style+20 XP
A cell has a cell wall, a cell membrane, ribosomes and plasmids, but no nucleus. What type of cell is it?
Exam style+20 XP
What is the function of the cell wall of a plant cell?
Exam style+20 XP
A photomicrograph of onion bulb cells shows a cell wall, cytoplasm, a nucleus and a vacuole, but no chloroplasts. Why?
Exam style+20 XP
Which structure is correctly matched with its function?
Skill unlocked
Animal, plant and bacterial cells, mastered.
This skill is now recorded on your profile. Keep the chain going.