Connect chlorophyll chloroplasts and energy transfer
Explain how a green pigment supports carbohydrate synthesis.
Exam scope and assessment notes
Core and Extended · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall chloroplasts, enzymes and the difference between photosynthesis and respiration.
- Use the stated observations, quantities and controls; diagrams are schematic.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which term names the cell structure?
What you will learn
- Explain how a green pigment supports carbohydrate synthesis.
- Use the stated evidence to explain the method and its limits.
Locate the pigment
Chlorophyll is a green pigment found in chloroplasts. A chloroplast is a cell structure; chlorophyll is a substance within that structure. The two names are related but do not identify the same thing.
Chlorophyll absorbs light and supports the transfer of energy from light into energy in chemicals during carbohydrate synthesis. A green leaf is not creating energy from nothing, and chlorophyll is not a food store replacing carbohydrate.
Link visible colour to function
A green region suggests chlorophyll is present, but colour alone does not measure photosynthetic rate. Water supply, carbon dioxide and temperature also influence the process. Use a controlled investigation before treating two differently coloured leaves as a rate comparison.
A microscope picture may use stains or fluorescence rather than natural colours. Identify chloroplasts from the supplied image evidence and key; a red fluorescence signal can represent chloroplasts even though chlorophyll is a green pigment in ordinary light.
Pause and explain
What energy transfer is required here?
Worked example
A palisade cell contains chloroplasts. Explain the role of chlorophyll without calling it a cell.
Show the worked solution
- Locate chlorophyll inside chloroplasts.
- Identify the pigment as green.
- Connect light absorption with energy transfer into carbohydrate chemicals.
Answer Chlorophyll is the green pigment in chloroplasts that supports light-to-chemical energy transfer for carbohydrate synthesis.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
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.
State the colour of chlorophyll and where it is found.
Give me a hint
Give a pigment property and a location.
Compare my reasoning
- Name green.
- Locate it in chloroplasts.
Chlorophyll is a green pigment in chloroplasts.
Look for these in your work
- Use the correct two terms.
- Include green.
Explain why chlorophyll should not be described as carbohydrate stored in the leaf.
Give me a hint
Compare the pigment role with the product.
Compare my reasoning
- Chlorophyll supports light-energy absorption and transfer.
- Carbohydrate is synthesised and can store chemical energy.
Chlorophyll is a pigment involved in energy transfer, whereas carbohydrate is a product that can be used or stored.
Look for these in your work
- Separate role and product.
- Do not imply the pigment is consumed as food.
An image key identifies red fluorescent spots as chloroplasts. A student rejects the key because chlorophyll is green. Correct the reasoning.
Give me a hint
The imaging method matters.
Compare my reasoning
- The display records fluorescence.
- Display colour need not match ordinary-light appearance.
- Use the documented signal identity and structures.
Red fluorescence can identify chloroplasts in that imaging method; it does not change the ordinary green-pigment description.
Look for these in your work
- Name fluorescence.
- Avoid identifying every coloured spot without a key.
Common mistakes
- A chloroplast is not the same as chlorophyll.
- A fluorescence display colour is not necessarily a natural pigment colour.
What can you explain now?
What energy transfer is required here?
Compare with the explanation
Light energy into energy in chemicals.
Carbohydrate synthesis stores transferred energy in chemicals.
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Make it stick
Connect pigment, organelle, light and chemical energy in one explanation.
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.