Test: Respiration - 1 - UPSC MCQ

Green plants prepare their own food by photosynthesis using simple inorganic substances such as carbon dioxide (CO₂) and water (H₂O) in the presence of sunlight and chlorophyll. Oxygen is released as a by-product of photosynthesis and is not used as a raw material in the process.

Cellular respiration is the process of breaking sugar into a form that the cell can use as energy. This happens in all forms of life. Cellular respiration takes in food and uses it to create ATP, a chemical which the cell uses for energy. Usually, this process uses oxygen, and is called aerobic respiration.

Bronchiole is a fine respiratory tube in the lungs of reptiles, birds and mammals. It is formed by the subdivision of a bronchus. 

Anaerobic respiration takes place in the absence of oxygen. In organisms such as yeast and plants, glucose is broken down into ethanol and carbon dioxide, releasing a small amount of energy.

Glucose → Ethanol + CO₂+ Energy

Hence, carbon dioxide is released during anaerobic respiration in these organisms.
(Note: In muscle cells, lactic acid is formed without release of CO₂, but standard school-level questions generally refer to yeast or plants.)

Explanation of the Breathing Cycle:

Aerobic respiration releases more energy because glucose is completely broken down using oxygen.
In anaerobic respiration, glucose is only partially broken down, so less energy is released.

The alveoli are the final branchings of the respiratory tree and act as the primary gas exchange units of the lung. Inhaled oxygen enters the lungs and reaches the alveoli. 

Respiration is a continuous and essential life process that occurs in all living cells of plants at all times. Unlike photosynthesis, which requires light, respiration occurs both during the day and at night, irrespective of the presence of sunlight. Therefore, plants respire in both light and dark conditions.

The exchange of gases in the alveoli occurs by simple diffusion due to differences in concentration of gases. Oxygen is present in higher concentration in the alveoli and diffuses into the deoxygenated blood in the surrounding capillaries. At the same time, carbon dioxide diffuses from the blood into the alveoli and is expelled during exhalation. This passive movement of gases occurs across the thin alveolar membrane without the use of energy.

the hemoglobin increases the oxygen carrying capacity of blood. In humans and most other vertebrates, the most common respiratory pigment is a protein called hemoglobin.