In plants, each part can independently take in oxygen from the air and give out carbon dioxide. Like all other living cells of the plants, the root cells take up air from the air spaces present between the soil particles.

Cellular respiration takes place in the cells all of organisms. In the cell, glucose is broken down into carbon dioxide and water with the release of energy. All organisms get energy through cellular respiration. 

Definition: 1 Mark
Cause: 1 Mark
Recovery: 1 mark
A muscle cramp is a painful contraction or tightening of the muscles for a few seconds. 
They happen when the cells in the muscle respire anaerobically. The glucose in the muscles is converted into lactic acid, and the lactic acid accumulation causes cramps.
Muscle cramps can be cured by massages or hot water bath because it improves blood circulation. Blood supplies oxygen to the muscle cells. Oxygen speeds up and completes the breakdown of lactic acid into carbon dioxide and water. 

Reason: 1 Mark
Product of anaerobic respiration: 1 Mark
Under anaerobic conditions, yeast produces alcohol. They are,  therefore, used to make wine and beer.
C₆H₁₂O₆  ---------------> 2C₂H₅OH + 2CO₂ + 2ATP
During anaerobic respiration, humans produce lactic acid in the muscles. The equation for this process is as follows:
Glucose ----------> Latic acid + Energy

Percentage of carbon dioxide: 1 Mark each
Percentage of carbon dioxide in the inhaled air is 0.04.
Percentage of carbon dioxide in the exhaled air is 4.4.

Part: 1 Mark each
1. Bronchus - The bronchus(plural: bronchi) are extensions of the windpipe that move air to and from the lungs.
2. Trachea - The trachea is a wide, hollow tube that connects the larynx to the bronchi of the lungs.
3. Lung - It is the main part of the respiratory system where the exchange of gases takes place.
4. Bronchioles - The bronchioles are the passageways through which air passes from the bronchi to the alveoli (air sacs) of the lungs.
5. Diaphragm - The diaphragm in the respiratory system is the dome-shaped sheet of muscle that separates the chest from the abdomen. It helps in breathing by expanding the chest cavity during inhalation and contracting it during exhalation.

Sore feet: 1 Mark
Hot water bath: 2 Marks
Lactic acid is a normal byproduct during anaerobic respiration in muscles, but it can irritate muscles and cause discomfort and soreness. Adding warm water increases the blood circulation around the sore area. As a result oxygen supply to the muscle cells also increases. The increase in the supply of oxygen results in the complete breakdown lactic acid into carbon dioxide and water. 
Skin appears red after a hot water bath. The reason as we know is that, warm water increases the blood circulation in that particular area.

Name of the part: 1 Mark
Statement: 1 Mark
Energy currency: 1 Mark
Mitochondria is the organelle in which cellular respiration takes place.
Prokaryotes are unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle. 
The energy currency of cell is ATP (Adenosine tri phosphate).