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The word equation for aerobic respiration is glucose + oxygen → carbon dioxide + water + energy. Free GCSE AQA notes with key terms and 12 questions answered.
Aerobic Respiration is part of Respiration in GCSE AQA Higher Biology.
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The word equation for aerobic respiration is glucose + oxygen → carbon dioxide + water + energy. Free GCSE AQA notes with key terms and 12 questions answered.
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Use this lesson to stay inside Respiration while connecting the detail back to the wider Bioenergetics topic.
Read the core explanations from Aerobic Respiration before testing yourself from memory.
Right now, your heart is beating, your brain is thinking, and your muscles are working. All of this requires energy. But where does this energy come from? The answer lies in a process happening millions of times per second inside every living cell in your body.
Your cells break down glucose (sugar) to release energy. This process needs oxygen from the air you breathe. Without it, you'd be unconscious in minutes. This energy-releasing process has a name: aerobic respiration.
Trap: Many students think respiration only happens when you breathe. Actually, breathing gets oxygen to your cells, but respiration is the chemical reaction inside cells that releases energy.
Aerobic respiration can be summarised in a simple word equation. Think of it as a recipe - glucose and oxygen go in, energy comes out along with carbon dioxide and water.
Notice the arrow shows the direction - glucose and oxygen are used up (reactants) to make carbon dioxide and water (products). Energy is released during this process, though we don't show it in the equation.
Exams expect you to know the chemical symbols for each substance in aerobic respiration. These symbols tell us exactly how many atoms of each element are involved.
The numbers in front (6O₂, 6CO₂, 6H₂O) show how many molecules are needed to balance the equation. One glucose molecule needs six oxygen molecules and produces six carbon dioxide molecules and six water molecules.
Aerobic respiration doesn't happen randomly in cells. It occurs in specific structures called mitochondria. These are the cell's power stations, converting glucose into usable energy.
Cells that need lots of energy (like muscle cells) have more mitochondria. Liver cells can have over 1000 mitochondria each because they're constantly working to process substances in your blood.
Trap: Students often say mitochondria are the powerhouse of the atom. They're the powerhouse of the cell, not the atom. Atoms don't have mitochondria!
Students often confuse respiration with photosynthesis because both involve glucose, oxygen, carbon dioxide and water. The key difference is the direction - they're opposite processes.
Worked example: Comparing Respiration and Photosynthesis
A student writes: 'Plants do photosynthesis, animals do respiration.' Explain what's wrong with this statement.
Answer: Plants do both photosynthesis (in light) and respiration (continuously). Animals only do respiration.
Here's the key difference: photosynthesis stores energy by making glucose, while respiration releases energy by breaking glucose down. They're opposite reactions.
Aerobic respiration questions appear frequently in GCSE exams. Here's how to avoid the most common mistakes and pick up full marks.
Exam depth extension: In aerobic respiration, connect why your cells need energy to the aerobic respiration equation using clear cause-and-effect statements. When you explain biological processes, include what changes, why it changes, and the consequence for cells, organisms, or populations. If calculations appear, show each step, include units, and end with a sentence that interprets the result in biological context.
For 6-mark questions about respiration, structure your answer: define the process, give the equation, explain where it happens, state what the energy is used for, and compare with photosynthesis if relevant.
Master these key points and you'll handle any respiration question with confidence. Remember: glucose + oxygen → carbon dioxide + water + energy. That's the foundation everything else builds on.
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Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
The word equation for aerobic respiration is glucose + oxygen → carbon dioxide + water + energy. Glucose and oxygen are the reactants that are used up, and carbon dioxide and water are the waste products; energy is released during the process.
Aerobic respiration is the process that releases energy from glucose using oxygen, producing carbon dioxide and water as waste products. It occurs continuously in living cells, and breathing is what gets the oxygen to the cells.
The products of aerobic respiration are carbon dioxide and water, which are waste products, and energy is released. The reactants are glucose and oxygen, so the word equation is glucose + oxygen → carbon dioxide + water.
The balanced symbol equation for aerobic respiration is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. One glucose molecule needs six oxygen molecules and produces six carbon dioxide molecules and six water molecules.
Respiration and photosynthesis are opposite reactions: photosynthesis stores energy by making glucose, while respiration releases energy by breaking glucose down. Plants do both, photosynthesis only in light and respiration all the time, while animals only respire because they lack chloroplasts.
Aerobic respiration happens in mitochondria, cellular organelles that have a folded inner membrane to increase surface area for energy production. Cells that need lots of energy, like muscle cells, have more mitochondria, and liver cells can have over 1000 each.
Liver cells can have over 1000 mitochondria each because they are constantly working to process substances in the blood and need lots of energy. Mitochondria are where aerobic respiration occurs, so cells that need lots of energy, like muscle cells, have more of them.
Plants do both photosynthesis and respiration, while animals only respire. Plants carry out photosynthesis only in light but respire all the time, day and night, because they need energy for growth; animals cannot carry out photosynthesis because they lack chloroplasts.
One glucose molecule needs six oxygen molecules in aerobic respiration and produces six carbon dioxide molecules and six water molecules. The numbers in front, 6O₂, 6CO₂ and 6H₂O, balance the equation.
Respiration and photosynthesis are opposite reactions because photosynthesis stores energy by making glucose from carbon dioxide and water, while respiration releases energy by breaking glucose down with oxygen into carbon dioxide and water.
Mitochondria have a folded inner membrane to increase the surface area for energy production. Mitochondria are the organelles where aerobic respiration occurs, converting glucose into usable energy.
A 6-mark answer on aerobic respiration should define the process, give the equation, explain where it happens (mitochondria), state what the energy is used for, and compare it with photosynthesis if relevant.