1.0 Introduction to Respiration
All living activities (running, thinking, growing) require energy. This energy is stored in food. Respiration is the biological process of releasing this energy from food (glucose).
Cellular Respiration: The process of breaking down food (glucose) in the cells with the help of oxygen to release energy, carbon dioxide, and water.
2.0 Aerobic vs. Anaerobic Respiration
Depending on whether oxygen is used or not, respiration is of two types:
| Feature | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| Oxygen | Occurs in the presence of Oxygen ($O_2$). | Occurs in the absence of Oxygen ($O_2$). |
| Energy Output | High (38 ATP). | Low (2 ATP). |
| Examples | Humans, Animals, Plants. | Yeast, Bacteria, Muscle cells. |
During heavy exercise, our muscles experience a deficiency of oxygen. They switch to Anaerobic Respiration, producing Lactic Acid. This accumulation causes pain and cramps.
3.0 Fermentation
What is Fermentation?
The anaerobic conversion of sugar into alcohol and carbon dioxide by yeast is called fermentation. This is why yeast is used to make bread, wine, and beer.
To confirm the release of $CO_2$ during respiration, we pass the gas through Lime Water. If it turns milky, $CO_2$ is present.
4.0 The Human Respiratory System
The human respiratory system is a network of organs that helps the body exchange gases. The path of air starts from the nose and ends in the lungs.
4.1 Key Organs & Their Roles
- 1 Nostrils & Nasal Passage: Air enters through nostrils. The hair and mucus inside the nose filter out dust and germs, while also warming the air.
- 2 Pharynx (Throat): A common passage for both air and food.
- 3 Larynx (Voice Box): Contains vocal cords that vibrate to produce sound when air passes through them.
- 4 Trachea (Windpipe): A long tube that carries air to the lungs. It is kept open by C-shaped cartilaginous rings.
The Epiglottis is a muscular flap that covers the opening of the trachea when we swallow food. This prevents food from entering our "windpipe."
4.2 Bronchi, Bronchioles, and Alveoli
Inside the lungs, the trachea divides into two Bronchi (one for each lung). These branch out into smaller tubes called Bronchioles, which finally end in tiny air-sacs called Alveoli.
Importance of Alveoli: They are surrounded by blood capillaries. This is where oxygen enters the blood and carbon dioxide leaves it.
- Lungs are spongy, elastic organs protected by the Rib Cage.
- They are covered by two thin membranes called Pleura.
- The left lung is slightly smaller (2 lobes) than the right lung (3 lobes).
5.0 Mechanism of Breathing
Breathing is a physical process that moves air in and out of the lungs. It involves two main phases: Inhalation and Exhalation. This movement is controlled by the Ribs and the Diaphragm.
5.1 Inhalation vs. Exhalation
| Feature | Inhalation (In) | Exhalation (Out) |
|---|---|---|
| Diaphragm | Moves Downwards (contracts) | Moves Upwards (relaxes) |
| Rib Cage | Moves Up and Out | Moves Down and In |
| Chest Cavity | Increases in size | Decreases in size |
| Air Flow | Air rushes Into lungs | Air pushed Out of lungs |
5.2 Inspired vs. Expired Air
The air we breathe out is different from the air we breathe in because our body uses Oxygen and produces Carbon Dioxide.
| Gas | Inspired (Inhaled) Air | Expired (Exhaled) Air |
|---|---|---|
| Oxygen | ~21% | ~16.4% |
| Carbon Dioxide | 0.04% | 4.0% |
| Nitrogen | 79% | ~79% (Not used) |
Did you know? We lose nearly half a litre of water every day just through breathing! You can see this as "fog" if you breathe out on a cold mirror.
Hiccups occur due to the sudden, involuntary movement of your diaphragm.
6.0 Common Respiratory Diseases
Our respiratory system can be affected by infections, pollution, or allergies. Here are the most common diseases students should know:
| Disease | Symptoms | Main Cause |
|---|---|---|
| Asthma | Shortness of breath, wheezing (whistling sound). | Allergens (dust, pollen) or pollution. |
| Bronchitis | Inflammation of bronchial tubes, constant coughing. | Viruses, smoking, or air pollution. |
| Pneumonia | Chest pain, chills, and high fever. | Bacterial or viral infection. |
| Tuberculosis (TB) | Continuous coughing, weight loss, and chest pain. | Infection by bacteria. |
- TB can be prevented using the BCG Vaccine.
- Bacterial infections like Pneumonia and TB are treated with Antibiotics (e.g., Penicillin, Streptomycin).
- Asthma is often managed using Inhalers (bronchodilators).
7.0 Summary of Air Path
To score full marks, remember the correct sequence of air travel:
Always distinguish between Breathing (Physical) and Respiration (Chemical). Breathing is just gas exchange; Respiration is energy production!