Year 7 Science · Unit 1 · Lesson 8
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Learning Goals
Match each term to its meaning
Write the letter of the correct meaning next to each term. Each letter is used once.
| Term | Letter | Meaning |
|---|---|---|
| Organelle | A. Jelly-like fluid that fills the cell | |
| Flexible | B. A specialised part inside a cell, with its own job | |
| Mitochondria | C. Control centre that holds the DNA | |
| Plasma membrane | D. Able to bend or change shape | |
| Cytoplasm | E. “Powerhouses” that release energy from food | |
| Nucleus | F. Thin outer layer of an animal cell that controls what enters and leaves |
1. Lucy thinks animal cells never contain vacuoles. Is she right? Describe how their vacuoles compare with the one in a plant cell.
Compare two
Fill in every empty box in the table.
| Feature | Plant cell | Animal cell |
|---|---|---|
| Cell wall | ||
| Chloroplasts | ||
| Outer layer or layers | ||
| Typical shape | ||
| Four parts found in both | ||
2. Draw a plant cell and an animal cell side by side. Label the four parts they share, and the three parts only the plant cell has.
Read the data
Scenario: are plant cells always bigger?
Mia looked at onion skin cells and her own cheek cells under a microscope. The onion cells looked huge, so she decided plant cells are always bigger than animal cells. Her teacher gave her Table 1. (1 µm, a micrometre, is one-thousandth of a millimetre.)
| Cell | Plant or animal | Approximate length (µm) |
|---|---|---|
| Human cheek cell | Animal | 60 |
| Guard cell from a leaf surface | Plant | 30 |
| Human egg cell | Animal | 120 |
| Onion skin cell | Plant | 250 |
| Human red blood cell | Animal | 8 |
Source: typical values, rounded, for this worksheet.
3. How many times longer is the human egg cell than the guard cell? Show your working.
Answer times longer
4. Use Table 1 to evaluate Mia’s claim. Suggest why onion cells can look bigger than cheek cells, and what cell size really depends on.
5. A kangaroo’s leg muscle cells need a lot of energy for jumping. Which organelle would you expect these cells to have in large numbers? Explain why, using what you know about how animal cells get their energy.
6. Explain why it makes sense that animal cells have only a flexible membrane on the outside, while plant cells also have a rigid cell wall. Use at least one example of an animal cell that has to change shape, and the phrase “structure fits function”.
Match each term to its meaning
Organelle → B; Flexible → D; Mitochondria → E; Plasma membrane → F; Cytoplasm → A; Nucleus → C.
Question 1
No: animal cells can have small vacuoles (1); a plant cell has one large central vacuole that fills most of the cell (1). [2 marks]
Compare two
Cell wall: plant yes (cellulose); animal no. Chloroplasts: plant yes (in cells that get light); animal no. Outer layers: plant, a rigid wall with a membrane inside it; animal, only a flexible membrane. Shape: plant box-like; animal flexible, irregular. Both: plasma membrane, cytoplasm, nucleus, mitochondria. [5 marks: 1 per row]
Question 2
Four shared parts (nucleus, cytoplasm, cell membrane, mitochondria) labelled in both cells (2: 1 per cell); cell wall, chloroplasts and large vacuole labelled in the plant cell only (2: all three = 2, two = 1). [4 marks]
Question 3
120 ÷ 30 (1) = 4 (1). [2 marks]
Question 4
Wrong: the egg (120 µm) and cheek cell (60 µm) are longer than the guard cell (30 µm) (1). Onion cells look big partly because of the large vacuole (1). Size depends on the job (1). [3 marks]
Question 5
Mitochondria (1): they release energy from food, and muscles need a lot to contract (1). [2 marks]
Question 6
Marking guide: 1 wall rigid, membrane flexible; 1 a wall would lock the cell in one shape; 1 example (white blood cell, muscle cell, egg cell); 1 why that needs no wall; 1 plants must stand without bones, so walls suit them; 1 “structure fits function” used. [6 marks]
Model answer: A wall is rigid; a membrane is flexible. A white blood cell squeezes out of a blood vessel and wraps around a bacterium, which it could not do in a rigid box. Plants must stand without bones, so walls suit them. Structure fits function.
Common error: “animal cells are smaller than plant cells”. Size depends on the job.