Quick answer: Breathing is the physical process of taking air into the lungs and pushing it out, driven by the diaphragm and rib muscles. Cellular respiration is the chemical process inside cells that breaks down glucose, using enzymes, to release energy as ATP. Breathing uses energy; cellular respiration releases it.
What is breathing?
Breathing is the physical movement of air into and out of the respiratory organs (lungs in humans). It brings in oxygen-rich air and removes air with more carbon dioxide. Gas exchange then happens by diffusion in the alveoli.
How breathing works in humans
| Stage | Muscles | Chest cavity | Result |
|---|---|---|---|
| Inhalation | Diaphragm contracts and flattens; rib muscles lift the ribs | Volume increases, pressure falls | Air moves into the lungs |
| Exhalation | Diaphragm relaxes and becomes dome-shaped; ribs move down | Volume decreases, pressure rises | Air moves out of the lungs |
Key features of breathing
- Physical process: It depends on muscle movement and pressure differences, not on chemical reactions.
- Outside the cells: It happens in the respiratory organs (nose, trachea, bronchi, lungs).
- No enzymes: Air simply moves in and out.
- Uses energy: The breathing muscles need energy (ATP) to contract. Breathing itself releases no energy.
- Only in some organisms: Animals with respiratory organs breathe. Plants exchange gases by diffusion through stomata and do not breathe in this sense.
What is cellular respiration?
Cellular respiration is the breakdown of food (mainly glucose) inside cells to release energy, which is stored as ATP (adenosine triphosphate). It takes place in many small, enzyme-controlled steps.
Stages of aerobic respiration
| Stage | Where it happens | What happens |
|---|---|---|
| Glycolysis | Cytoplasm | Glucose (6-carbon) is broken into 2 pyruvate (3-carbon) molecules, with a small amount of ATP |
| Breakdown of pyruvate | Mitochondria | In the presence of oxygen, pyruvate is broken down completely to carbon dioxide and water, releasing much more energy |
The overall equation for aerobic respiration is:
Key features of cellular respiration
- Biochemical process: A chain of oxidation reactions.
- Inside the cells: First in the cytoplasm, then in the mitochondria.
- Needs enzymes: Each step is controlled by a specific enzyme.
- Releases energy: The energy is used to make ATP, the "energy currency" of the cell.
- Happens in all living cells: Plants, animals, fungi and bacteria all respire.
How much ATP? Older textbooks state that one glucose molecule gives about 38 ATP in aerobic respiration. Current estimates are lower, about 30–32 ATP, because some energy is used in moving molecules across the mitochondrial membrane. NCERT Class 10 does not ask for the number, so focus on "much more energy is released in aerobic than in anaerobic respiration".
Breathing vs cellular respiration
| Basis | Breathing | Cellular respiration |
|---|---|---|
| Nature | Physical (mechanical) process | Biochemical process |
| Site | Respiratory organs, e.g. lungs | Inside cells: cytoplasm and mitochondria |
| Enzymes | Not involved | Many enzymes involved |
| Energy | Uses energy (muscle work) | Releases energy as ATP |
| Purpose | Moves air in and out for gas exchange | Breaks down glucose to release energy |
| Occurs in | Animals with respiratory organs | All living cells |
Key idea: Breathing supplies the oxygen and removes the carbon dioxide; cellular respiration is where the oxygen is actually used and the carbon dioxide is produced.
Exam tips
- In a "differentiate" question, use a two-column table with at least four points: nature, site, enzymes and energy.
- Write the word equation or the balanced chemical equation for aerobic respiration.
- Say clearly that glycolysis happens in the cytoplasm and the complete breakdown of pyruvate happens in the mitochondria.
- Link the two: oxygen taken in by breathing is carried by blood to cells for cellular respiration.
Common mistakes
- Using "breathing" and "respiration" as if they mean the same thing.
- Saying breathing produces energy. It uses energy; respiration releases it.
- Saying plants breathe through their lungs or do not respire. Plants do not breathe, but every living plant cell respires.
- Writing that all of respiration happens in the mitochondria. Glycolysis happens in the cytoplasm.
Frequently Asked Questions
What is the difference between breathing and respiration?
Breathing is the physical movement of air into and out of the lungs. Respiration is the chemical breakdown of glucose inside cells to release energy as ATP.
Where does cellular respiration take place?
It starts in the cytoplasm (glycolysis) and is completed in the mitochondria when oxygen is available.
Does breathing produce energy?
No. Breathing uses energy, because the diaphragm and rib muscles must contract. The energy is released later, by cellular respiration inside the cells.
How many ATP are produced from one glucose molecule?
Older textbooks give about 38 ATP for aerobic respiration. Modern estimates are about 30–32 ATP. Class 10 exams usually ask only which type of respiration releases more energy.
Do plants breathe?
Plants do not breathe like animals, since they have no lungs or breathing movements. They exchange gases by diffusion through stomata and lenticels, but all their cells carry out respiration.