Locate chemical energy in an organism
Organic molecules in living material contain chemical energy that can be transferred when organisms feed.
Section B15.1 · Energy flow
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Use organic molecules and feeding as context; detailed digestion is taught in the nutrition pathway.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Where is chemical energy stored in a living organism?
What you will learn
- Identify chemical energy in organic material
- Distinguish an organism’s energy store from the organism itself
Describe the stored form
Living organisms contain organic molecules. These molecules have chemical energy that can be transferred to another organism when material is eaten and digested. For example, a plant stores chemical energy in the organic substances in its tissues.
In a simple energy pathway, label the store as chemical energy in the organism or in its organic material. A plant is not “made of energy”: it is matter containing molecules with chemical energy.
Separate energy from matter
Food contains matter and chemical energy. During digestion, food molecules are broken down and absorbed; during metabolism, cells use molecules in many reactions. Energy is transferred through these processes, while atoms and molecules are matter that can be rearranged.
Keep this section qualitative. The syllabus requires you to describe energy forms and movement through organisms; it does not require you to calculate energy stores or compare food calories here.
Sources for this lesson
Pause and explain
Which label best describes energy in a leaf before a caterpillar eats it?
Worked example
A caterpillar eats a leaf. Name the energy form in the leaf tissue before feeding.
Show the worked solution
- Recognise the plant tissue as organic material.
- Identify the energy stored in its molecules.
Answer The leaf tissue contains chemical energy in organic molecules. Feeding can transfer some of this chemical energy to the caterpillar.
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.
Label the energy form in grass before it is eaten by a rabbit.
Give me a hint
Name the chemical store.
Compare my reasoning
- Grass contains organic molecules.
- Those molecules contain chemical energy.
Chemical energy is present in organic molecules in the grass before feeding.
Look for these in your work
- Correct form
- Correct location
A learner says “the rabbit eats energy.” Improve this sentence scientifically.
Give me a hint
Include both food matter and its energy.
Compare my reasoning
- The rabbit eats plant material containing organic molecules.
- Some chemical energy in that material can be transferred to the rabbit.
The rabbit eats plant material; its organic molecules contain chemical energy that can be transferred during feeding and digestion.
Look for these in your work
- Matter described
- Energy transfer described
A leaf is dried but remains as organic plant material. Does removing water mean its chemical energy has become matter? Explain the distinction.
Give me a hint
Energy and material are different categories.
Compare my reasoning
- The leaf is matter made of molecules.
- Those molecules can contain chemical energy; drying changes water content but does not make energy into matter.
No. The leaf is matter containing molecules with chemical energy. Removing some water changes the material composition; it does not turn energy into matter.
Look for these in your work
- Categories separated
- No unsupported energy calculation
Common mistakes
- Calling an organism an energy form
- Confusing chemical energy with the matter in food
- Adding an unrequired numerical energy value
What can you explain now?
Where is chemical energy stored in a living organism?
Compare with the explanation
In organic molecules
These are matter molecules that contain transferable chemical energy.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Explain where chemical energy is found in living material and why food and energy are not synonyms.
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.