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Respiration is a set of reactions in cells that transfers energy for processes such as movement, active transport and maintaining body temperature. Aerobic respiration uses oxygen and glucose to form carbon dioxide and water. Cells respire continuously, including plant cells. Photosynthesis stores energy in organic molecules while respiration makes that energy available for cellular work; plants do not replace respiration with photosynthesis during daylight.
Video by Cognito. The video’s own board label is retained; follow the specification reference and scope notes on this lesson for assessed content.
Viewing focus: Compare aerobic and anaerobic respiration
After watching, attempt these questions before opening the answers. You can also use the written lesson below.
After watching 1: Do plants respire in daylight?
Yes. Living cells require energy continuously.
After watching 2: What are yeast fermentation products?
Ethanol and carbon dioxide. Yeast’s pathway differs from human muscle.
What you'll be able to do
Respiration is a set of reactions in cells that transfers energy for processes such as movement, active transport and maintaining body temperature. Aerobic respiration uses oxygen and glucose to form carbon dioxide and water. Cells respire continuously, including plant cells. Photosynthesis stores energy in organic molecules while respiration makes that energy available for cellular work; plants do not replace respiration with photosynthesis during daylight.
When oxygen supply cannot meet demand, muscle cells can convert glucose to lactic acid, transferring less energy per glucose than aerobic respiration. Yeast can ferment sugars to ethanol and carbon dioxide. These are different anaerobic pathways, so do not use the yeast products in a human-muscle equation. During exercise, breathing and heart rate rise to supply oxygen and glucose and remove carbon dioxide. Recovery includes processing lactate and restoring conditions.
A respirometer can measure gas-volume change linked to oxygen uptake when carbon dioxide is absorbed by a suitable reagent. Keep temperature controlled and compare equal masses or standardised organisms. Include an appropriate control to detect non-respiratory volume change. Germinating seeds can demonstrate respiration, but dead or dormant material may behave differently. Interpret the measurement mechanism before concluding that every capillary movement directly counts oxygen molecules without any assumptions.
Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.
Common mistakes to avoid
Key takeaways
Question 1: Why place a respirometer in a constant-temperature environment?
It controls both a physical and a biological influence.
Check the assessed scope and practical or mathematical requirements.
An external explanation or interactive activity to use alongside the lesson. It may include extension material.
Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.