Respiration

 

Aerobic respiration

Respiration is a process that breaks down glucose to release energy in every cell of the human body. It is different from ventilation, which is breathing. Without respiration, cells would die.

 

Respiration that uses oxygen is called aerobic respiration. The formula for aerobic respiration is:

 

glucose + oxygen → carbon dioxide + water

 

Aerobic respiration releases a lot of energy from glucose slowly. It happens mostly in mitochondria, which are tiny parts of the cells in the cytoplasm. Cells that need more energy, such as sperm cells or muscle cells, have more mitochondria.

 

Anaerobic respiration

When the body’s cells do not get enough oxygen during intense exercise, they switch from aerobic to anaerobic respiration. Anaerobic respiration has this formula:

 

glucose → lactic acid

 

Anaerobic respiration produces less energy than aerobic respiration, but it does it faster. However, it also makes lactic acid, which accumulates in the muscles and causes pain, tiredness, and cramps.

 

After intense exercise, people keep breathing fast and deep for a while. This is called excess post-exercise oxygen consumption or EPOC. It used to be called ‘oxygen debt.’ During this time, oxygen reacts with lactic acid to make carbon dioxide and water, and release the rest of the energy from glucose.

 

Comparing aerobic and anaerobic respiration

	Reactant(s)	Products(s)	Rate of reaction	Energy released
Aerobic respiration	Glucose, oxygen	Carbon dioxide, water	Slow	More
Anaerobic respiration	Glucose	Lactic acid	Fast	Less

 

 

🔬 Knowledge Check: Respiration

Test your knowledge of how energy is released in living organisms.

1. What are the waste products of aerobic respiration?

• Glucose and oxygen
• Carbon dioxide and water
• Lactic acid and ethanol

2. Why is anaerobic respiration considered less efficient than aerobic respiration?

• It releases much less energy from each glucose molecule.
• It uses too much oxygen.
• It only happens in plants.

3. Which substance is produced during anaerobic respiration in humans that causes muscle fatigue?

• Ethanol
• Lactic acid
• Carbon dioxide

4. In yeast, the process of anaerobic respiration is also known as:

• Photosynthesis
• Fermentation
• Combustion

5. Which part of the cell is the site for aerobic respiration?

• Cytoplasm
• Mitochondria
• Nucleus

Click to Reveal Answers

1. Carbon dioxide and water (These are the chemical byproducts of aerobic respiration).
2. Releases much less energy (Because glucose is not fully broken down).
3. Lactic acid (Produced when oxygen is in short supply during hard exercise).
4. Fermentation (A process used in biotechnology to produce bread and beer).
5. Mitochondria (Anaerobic respiration occurs in the cytoplasm, but aerobic occurs here).

 

Summary:

 

• Respiration is a process that breaks down glucose to release energy in all living cells.
• Oxygen is needed for aerobic respiration, which produces more energy but slower.
• Anaerobic respiration happens without oxygen, which produces less energy but faster.