Connect nutrition and cellular respiration
Separate obtaining materials from releasing usable energy in cells.
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
- Read the stated observations before choosing a group.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Where does cellular respiration occur?
What you will learn
- Describe nutrition in plants and animals.
- Distinguish cellular respiration from breathing.
Materials enter before they are used
Nutrition supplies materials needed for energy, growth and development. Animals obtain organic nutrients from food. Green plants take in water and mineral ions and use carbon dioxide in photosynthesis to make organic substances. A plant does not obtain all its food by absorbing soil.
Respiration is a set of chemical reactions inside cells that breaks down nutrient molecules and releases energy for other cellular activities. Metabolism means the collection of chemical reactions in an organism; respiration supports many of them.
Breathing and respiration are different
Breathing moves air into and out of lungs. It helps supply oxygen in humans, but the energy-releasing reactions take place in cells throughout the body. A germinating seed can respire without lungs.
An observation that oxygen is used or carbon dioxide produced can support an investigation of respiration under specified conditions. It does not mean that every respiratory process requires oxygen; anaerobic respiration is developed later in the course.
Sources for this lesson
Pause and explain
Which statement links nutrition and respiration correctly?
Worked example
A germinating seed releases carbon dioxide but has no lungs. Explain how it can still respire.
Show the worked solution
- Respiration is a chemical process in cells.
- Stored nutrient molecules are broken down.
- Released energy supports growth and other cellular activity.
Answer The seed respires in its cells; lungs and breathing are not required.
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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.
A rabbit eats grass and its cells break down nutrients to release energy. Name each process.
Give me a hint
Identify intake first, then the cellular reaction.
Compare my reasoning
- Eating supplies nutritional materials.
- Breaking down nutrients in cells is respiration.
- Energy supports cellular activities.
Eating: nutrition; cellular energy release: respiration.
Look for these in your work
- Assign both processes correctly.
- Mention cells in the respiration explanation.
Explain why a root cell can respire even though it does not photosynthesise.
Give me a hint
Photosynthesis makes organic substances; respiration uses nutrients.
Compare my reasoning
- Organic nutrients can reach the root from other plant tissues.
- The root cell breaks down nutrients.
- Energy is released for its activities.
A root cell uses supplied nutrients in energy-releasing reactions.
Look for these in your work
- Do not require a chloroplast for respiration.
- Connect nutrient breakdown with energy release.
A student says fish do not respire because they do not breathe through lungs. Evaluate the claim.
Give me a hint
Separate gas exchange structures from cellular reactions.
Compare my reasoning
- Many fish exchange gases using gills.
- Their living cells carry out respiration.
- Absence of lungs does not imply absence of respiration.
The claim is false: fish cells respire, with gills supporting gas exchange.
Look for these in your work
- Reject the claim with a cellular mechanism.
- Avoid treating breathing and respiration as synonyms.
Common mistakes
- Respiration does not mean ventilation of lungs.
- Plants respire as well as photosynthesise.
What can you explain now?
Does eating and digesting a meal alone describe respiration?
Compare with the explanation
No.
Nutrition obtains materials; respiration involves energy-releasing chemical reactions inside cells.
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Make it stick
Explain nutrition and respiration without using breathing as their definition.
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.