Cells
Clear notes with worked examples, then 4 practice questions with answers. Written by Beyond Tutors tutors for the KS3 National Curriculum.
All living things are made of cells
Animal and plant cells both have
- Nucleus: contains DNA, controls the cell
- Cell membrane: controls what goes in and out
- Cytoplasm: jelly where chemical reactions happen
- Mitochondria: where respiration releases energy
Only plant cells have
- Cell wall: made of cellulose, keeps the cell rigid
- Chloroplasts: where photosynthesis happens (contain green chlorophyll)
- Permanent vacuole: filled with cell sap, keeps the cell firm
Levels of organisation
cell → tissue → organ → organ system → organism
e.g. muscle cell → muscle tissue → heart → circulatory system → you
Specialised cells
- Red blood cell: no nucleus, more room to carry oxygen
- Root hair cell: long and thin to absorb water
- Sperm cell: tail to swim
Using a microscope
Start on the lowest power, focus with the coarse knob, then the fine knob.
Practice questions
Try each one, then tap to see the answer and why.
- Question 1 · Cells
What is the cell wall of a plant cell made of?
- AProtein
- BStarch
- CCellulose
- DFat
Show the answer
C: Cellulose
Plant cell walls are made of cellulose, which keeps the cell rigid.
- Question 2 · Specialised cells
Why does a red blood cell have no nucleus?
- ASo it can divide faster
- BTo have more room to carry oxygen
- CSo it can swim
- DTo make it stronger
Show the answer
B: To have more room to carry oxygen
Without a nucleus there is more space for haemoglobin, which carries oxygen.
- Question 3 · Cells
What does the nucleus contain?
- ACell sap
- BChlorophyll
- CGenetic material (DNA)
- DAir
Show the answer
C: Genetic material (DNA)
The nucleus holds DNA, the instructions that control the cell.
- Question 4 · Cells
Which cell part is the site of respiration?
- ANucleus
- BChloroplast
- CMitochondria
- DVacuole
Show the answer
C: Mitochondria
Mitochondria release energy from glucose by respiration.