Connect ribosomes mitochondria and chloroplasts with their roles
Distinguish protein production, aerobic respiration and photosynthesis.
Section B2.1 · Cell structure
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall the distinction between plant, animal and bacterial cells. Read the supplied evidence before drawing a conclusion.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which structure is a site of protein synthesis?
What you will learn
- Identify ribosomes, mitochondria and chloroplasts.
- Explain why photosynthetic cells also respire.
Different chemical tasks
Ribosomes are sites of protein synthesis. They occur in plant, animal and bacterial cells. In a schematic they may be drawn as dots, but not every dot in a photograph is a ribosome; resolving such small structures requires suitable imaging evidence.
Mitochondria are sites of aerobic respiration in typical plant and animal cells, releasing energy for cell activities. They do not create energy from nothing. A plant cell with chloroplasts still needs respiration; photosynthesis and respiration are different processes.
Light capture has a separate role
Chloroplasts contain chlorophyll and are sites of photosynthesis in photosynthetic plant cells. Chlorophyll absorbs light energy used to make organic molecules. Chloroplasts do not replace ribosomes or mitochondria.
A bacterial cell has ribosomes but does not have mitochondria or chloroplasts in the typical syllabus model. Lack of mitochondria does not mean a bacterium cannot release energy; its respiration is organised differently.
Sources for this lesson
Pause and explain
Which pair of processes can occur in the same leaf cell?
Worked example
A leaf-cell sketch labels tiny dots A, folded internal structures B and chlorophyll-containing structures C. Match them with functions.
Show the worked solution
- A ribosomes: protein synthesis.
- B mitochondria: aerobic respiration.
- C chloroplasts: photosynthesis.
Answer A protein synthesis; B aerobic respiration; C photosynthesis.
Try a topic test
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Match ribosome and mitochondrion to protein synthesis and aerobic respiration.
Give me a hint
Match one task to each structure.
Compare my reasoning
- Ribosome makes proteins.
- Mitochondrion is a site of aerobic respiration.
Ribosome: protein synthesis; mitochondrion: aerobic respiration.
Look for these in your work
- Correct two matches.
- Use named processes.
Explain why a root hair cell can have mitochondria but no chloroplasts.
Give me a hint
Separate energy release from light-driven synthesis.
Compare my reasoning
- The root cell requires energy from respiration.
- Its usual underground position does not support photosynthesis.
Respiration is needed; photosynthesis is not its specialised role.
Look for these in your work
- Mention respiration.
- Do not call the cell an animal cell.
A student reports ribosomes in a bacterium and concludes it must have mitochondria. Evaluate the inference.
Give me a hint
Sharing one structure does not imply sharing every structure.
Compare my reasoning
- Bacterial cells synthesise proteins using ribosomes.
- They lack mitochondria in this model.
- Respiration is not proof of mitochondria.
The inference is invalid; bacterial ribosomes do not imply mitochondria.
Look for these in your work
- Keep protein synthesis separate.
- State the bacterial distinction.
Common mistakes
- Plants also respire.
- Mitochondria release energy through respiration, rather than manufacture energy.
What can you explain now?
Why does a photosynthetic cell need mitochondria?
Compare with the explanation
It uses aerobic respiration to release energy for cell activities.
Photosynthesis does not eliminate the need for respiration.
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Make it stick
Link each organelle to its chemical process and give one mistaken match.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.