Cell specialisation – Form follows function
A muscle cell contracts many times each minute. Which organelle would you expect it to contain in large numbers?
Lysosomes
Nuclei
Mitochondria
Golgi apparatus
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A muscle cell contracts many times each minute. Which organelle would you expect it to contain in large numbers?
Lysosomes
Nuclei
Mitochondria
Golgi apparatus
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Most body cells with a nucleus contain the same DNA. How can a nerve cell and a muscle cell still be different?
Different gene use
No DNA in muscle cells
Only nerve cells use DNA
Random loss of organelles
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What differences can you see?
Duration: 2 minutes. Slide type: word cloud. Show side-by-side, unlabelled but accurate diagrams of a nerve cell and an elongated muscle cell. Prompt: “Look at both cells. Enter one visible difference in their shape or structure.” Expected responses include: nerve cell has many branches; nerve cell has one very long extension; muscle cell is long and fibre-shaped; muscle cell looks thicker; nerve cell spreads in several directions. Accept observations, not explanations, at this stage. Ask: “Could their different shapes be connected to different jobs?”
What is a specialised cell?
A specialised cell has structures and features suited to a particular function.
In a multicellular organism, different cells perform different jobs. Most body cells contain the same DNA, but they use different genes and make different proteins
Different proteins → different structures → different functions
Duration: 3 minutes. Explain each arrow. Keep the gene explanation short and connect it to the previous lesson. Do not teach embryonic development or gene regulation mechanisms.
Form follows function
“A cell’s structure helps it perform its function.”
Weak answer:
“A nerve cell has a long axon.”
Strong answer:
“A nerve cell has a long axon, which allows an electrical signal to travel over a long distance.”
feature → how it helps → function
“The cell has ___, which allows it to ___.”
Duration: 3 minutes. Think aloud: the weak answer only identifies a feature; the strong answer explains the biological advantage.
Which sentence best explains the idea that form follows function in biology?
A nerve cell has branches.
Nerve cells look interesting under a microscope.
A nerve cell’s branched extensions help it receive signals from many cells.
A muscle cell and a nerve cell are both cells.
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Which statement best defines a specialised cell?
A cell with features suited to one job
A cell with completely different DNA
A cell with no organelles at all
A cell that changes shape randomly
Correct answer: ‘A cell with features suited to one job’. Feedback: correct because specialisation means structures and features are suited to a particular function. Misconceptions: ‘different DNA’ confuses DNA with gene use; ‘no organelles’ is biologically incorrect; ‘changes shape randomly’ ignores the structure–function link. Use after slides 4–6 as a check on the core definition and principle.
Why do they look different?
Open question
“A nerve cell and a muscle cell have different tasks. Explain why it is logical that they have different shapes and structures.”
Write two or three complete sentences. Include one feature of each cell.
Duration: 4 minutes. Expected answer: “Their structures are suited to their different functions. A nerve cell has branches and a long axon so that it can receive and transmit signals over long distances. A muscle cell is a long fibre with contractile proteins and many mitochondria so that it can contract repeatedly and produce force.” Assessment criteria: states that structure is related to function; correctly links one nerve-cell feature to signalling; correctly links one muscle-cell feature to contraction or energy demand. Students first answer independently. Discuss why “They have different jobs, so they look different” is true but incomplete without a concrete structural explanation.
Levels of organisation in living things
A specialised cell works with similar cells in a tissue. Different tissues form an organ. Several organs can work together in an organ system. All systems together form an organism.
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What is the correct order from smallest to largest?
cell → organ → tissue → organism
tissue → cell → organ → organism
cell → tissue → organ → organism
cell → tissue → organ → organ system → organism
Correct answer: ‘cell → tissue → organ → organ system → organism’. Feedback: correct because this is the complete biological hierarchy. Misconceptions: the other options mix up the order or omit organ system. After checking answers, remind students that the shortened order cell → tissue → organ → organism is only used when ‘organ system’ is not one of the given terms.
