The shape of the lesson
By the end of the lesson, learners can
- Inside an animal cell: Rotate the animal cell and click each organelle to read its function.
- What a plant cell adds: Now rotate the plant cell.
- Powered by ATP: Every step in Fig. 1 costs energy, and the cell pays for all of it in one currency.
- Protein route: rough ER, vesicle, Golgi body, secretory vesicle, exocytosis.
- Double membrane: nucleus, mitochondrion, chloroplast.
- Ribosomes: 80S in cytoplasm, 70S in mitochondria and chloroplasts.
- Plant only: wall, chloroplasts, large vacuole, plasmodesmata.
One picture every idea returns to
All living organisms are made of cells, the basic units of life. A eukaryotic cell has a nucleus and many membrane-bound organelles, each with its own function. Proteins for secretion are made on 80S ribosomes on the rough ER, modified in the Golgi body and released by exocytosis. Mitochondria and chloroplasts have a double membrane, their own small circular DNA and 70S ribosomes. Plant cells add a cellulose cell wall, chloroplasts, a large permanent vacuole and plasmodesmata; animal cells have centrioles. Cells use ATP from respiration for every energy-requiring process.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, A cell is a factory with departments.. The electron microscope revealed that a eukaryotic cell is packed with membrane-bound compartments, each with its own job. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: Inside an animal cell | Rotate the animal cell and click each organelle to read its function. Project tab 1 of the lab (Cell structure lab, 3D animal cell) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: What a plant cell adds | Now rotate the plant cell. Project tab 2 of the lab (Cell structure lab, 3D plant cell) and let a student drive it while the class predicts. | Pairs |
| 21 to 30 min | Teach and check: Powered by ATP | Every step in Fig. 1 costs energy, and the cell pays for all of it in one currency. | Anticipation / Reaction Guide |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 20 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Powered by ATP, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Anticipation / Reaction Guide
Before the lesson, students mark five statements true or false. After the teaching they mark them again and justify any change of mind in one sentence each. The statements come from the examiner traps below.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Do not confuse cilia and microvilli. | Cilia are longer, contain microtubules and move; microvilli are much smaller folds that only increase surface area. And ribosomes have no membrane: they are not membrane-bound organelles. |
| ATP does not “make” energy and is not a long-term store. | It transfers energy from respiration to the processes that need it, and each molecule is recycled within seconds of being made. |
Animal and plant cells: worksheet
6 questions, 20 marks. Written in the style of the papers; no past paper question is reproduced.
State the function of: (a) smooth endoplasmic reticulum, (b) a lysosome, (c) plasmodesmata, (d) centrioles.
Describe the roles of the organelles involved in making and secreting an extracellular enzyme.
Give four structural differences between a typical palisade mesophyll cell and a typical liver cell.
Outline the structure of a mitochondrion as seen with an electron microscope.
Distinguish between cilia and microvilli.
State what is meant by ATP and give two energy-requiring processes in cells that use it.
Answer key and marking notes
- (a) makes lipids and steroids (and stores calcium ions).
- (b) contains hydrolytic enzymes that digest worn-out organelles or engulfed material.
- (c) link the cytoplasm of neighbouring plant cells through the cell walls.
- (d) organise the spindle (microtubules) during cell division.
- The gene is transcribed in the nucleus and mRNA leaves through a nuclear pore.
- The enzyme is made on ribosomes on the rough ER and folded and transported in its cisternae.
- Vesicles carry it to the Golgi body, where it is modified and packaged into secretory vesicles.
- Secretory vesicles fuse with the cell surface membrane and release it by exocytosis; mitochondria supply ATP.
- The palisade cell has a cellulose cell wall; the liver cell has none.
- The palisade cell has chloroplasts; the liver cell has none.
- The palisade cell has a large permanent vacuole with a tonoplast; the liver cell has only small temporary vacuoles.
- The liver cell has centrioles; the palisade cell has none (also accept: plasmodesmata in the plant cell; starch grains versus glycogen granules).
- A double membrane (envelope); the inner membrane is folded into cristae.
- A matrix enclosed by the inner membrane.
- The matrix contains small circular DNA and 70S ribosomes.
- Cilia contain microtubules (9 + 2 arrangement) and beat to move fluid or mucus across the cell surface.
- Microvilli are small folds of the cell surface membrane with no microtubule core; they do not move but increase the surface area for absorption.
- ATP is adenosine triphosphate, the molecule that transfers energy from respiration to energy-requiring processes; it is hydrolysed to ADP and phosphate.
- Any two of: active transport, protein synthesis, DNA replication or cell division, muscle contraction, exocytosis, movement of cilia.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which organelle is surrounded by a single membrane?
- Alysosome
- Bmitochondrion
- Cnucleus
- Dchloroplast
The drawing shows part of an animal cell as seen in an electron micrograph. Which labelled structure is the Golgi body?
- AC
- BB
- CA
- DD
Which structure is present in a palisade mesophyll cell but absent from a root hair cell of the same plant?
- Achloroplasts
- Ba cellulose cell wall
- Ca large permanent vacuole
- Dmitochondria
Which statement about centrioles is correct?
- AThey are made of microtubules and are found in animal cells but not in typical plant cells.
- BThey are surrounded by a double membrane and assemble the ribosome subunits.
- CThey are found in both animal and plant cells and lay down the cellulose cell wall.
- DThey are made of actin filaments and contain small circular DNA.
Which cell would be expected to contain the greatest number of mitochondria?
- Aa kidney tubule cell that reabsorbs glucose by active transport
- Ba mature red blood cell carrying oxygen
- Ca fat-storage cell in adipose tissue
- Da xylem vessel element in a plant stem
The table shows the percentage of the total membrane area in two animal cells, P and Q, that belongs to each type of membrane. Which conclusion is best supported by the data?
- ACell P is specialised to make and secrete large amounts of protein.
- BCell Q contains more mitochondria than cell P.
- CCell P has a larger total membrane area than cell Q.
- DCell P synthesises no lipids at all.
A cell secretes a digestive enzyme. A drug is added that stops vesicles budding off the Golgi body but has no other effect. Where will the newly made enzyme accumulate?
- Ain the Golgi body
- Bin the nucleus
- Cin the lysosomes
- Din the cytoplasm around free ribosomes
An electron micrograph of a cell shows 80S ribosomes, mitochondria, a cell wall and a large vacuole surrounded by a tonoplast. No chloroplasts and no centrioles are seen. Which type of cell could this be?
- Aa cell from the cortex of a plant root
- Ba liver cell from a mammal
- Ca bacterial cell
- Da palisade mesophyll cell from a leaf
Quiz key
A lysosome is a vesicle bounded by a single membrane that holds hydrolytic enzymes. Mitochondria have a double membrane, with the inner one folded into cristae. The nucleus is enclosed by the nuclear envelope, which is two membranes perforated by nuclear pores. Chloroplasts also have a double-membrane envelope around the stroma and thylakoids.
C is a stack of curved, flattened cisternae with vesicles at the edges: the Golgi body, which modifies proteins and packages them into vesicles. B is also a set of flattened sacs, but its membranes are studded with ribosomes (the dots), so it is rough endoplasmic reticulum. A is the nucleus: a large structure bounded by a double envelope with a dense nucleolus inside. D is a mitochondrion, recognised by its double membrane and the folded inner membrane (cristae).
Root hair cells are underground and receive no light, so they have no chloroplasts; palisade cells are packed with them for photosynthesis. Both cells have a cellulose cell wall and a large permanent vacuole surrounded by a tonoplast, because these are features of typical plant cells. Both cells also have mitochondria: every living plant cell respires, and root hair cells need a lot of ATP for the active uptake of mineral ions.
Each centriole is a short cylinder of microtubules (nine triplets); a pair lies near the nucleus of an animal cell and helps organise the spindle in cell division. Typical plant cells have no centrioles. Centrioles have no membrane, and ribosome subunits are assembled in the nucleolus. Cellulose walls are made by enzymes in the cell surface membrane of plant cells, not by centrioles. Centrioles are made of the protein tubulin (as microtubules), not actin, and the organelles that contain small circular DNA are mitochondria and chloroplasts.
Active transport uses ATP to move substances against a concentration gradient, so kidney tubule cells that reabsorb glucose have very many mitochondria, often packed close to the membrane. A mature mammalian red blood cell has no mitochondria at all (it respires anaerobically). A fat-storage cell is mostly one large lipid droplet with few organelles and a low energy demand. A xylem vessel element is dead when mature, with no cytoplasm and no organelles.
In cell P most of the membrane (60%) is rough ER, with a large Golgi body and many secretory vesicles: the pattern of a cell, such as a pancreatic cell, that makes protein on ribosomes and exports it by exocytosis. Cell Q has a higher percentage of mitochondrial membrane, but a percentage of an unknown total cannot show that it has more mitochondria. For the same reason the data say nothing about which cell has the larger total membrane area. Less than 1% smooth ER shows that lipid synthesis is minor in cell P, not absent; every cell must make phospholipids for its membranes.
The enzyme is made on ribosomes of the rough ER, travels in vesicles to the Golgi body, and then leaves the Golgi in secretory vesicles. If vesicles cannot bud from the Golgi, the enzyme still arrives there but cannot leave, so it builds up in the Golgi cisternae. Proteins are not made in the nucleus; only the mRNA comes from there, and that step is unaffected. Lysosomes are themselves formed from Golgi vesicles, so the enzyme cannot reach them either. A secreted protein is made by ribosomes on the rough ER and passes into its cisternae, not into the cytoplasm.
A cell wall, a large vacuole with a tonoplast and no centrioles all indicate a plant cell, and the absence of chloroplasts fits a cell that is not exposed to light, such as a root cortex cell. A liver cell has no cell wall and no large permanent vacuole, and it does have centrioles. A bacterium has only 70S ribosomes and no organelles bounded by double membranes, so it has no mitochondria. A palisade mesophyll cell would show many chloroplasts.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.