Chapter 05 Life Processes Questions-03
Questions
1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
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Answer
Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals need to utilize oxygen present in the water. Air contains more $O_2$ as compared to water. Since the content of $O_2$ in air is high, the terrestrial animals do not have to breathe faster to get more oxygen. Therefore, unlike aquatic animals, terrestrial animals do not have to show various adaptations for better gaseous exchange.
2. What are the different ways in which glucose is oxidised to provide energy in various organisms?
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Answer
Glucose is first broken down in the cell cytoplasm into a three carbon molecule called pyruvate. Pyruvate is further broken down by different ways to provide energy. The breakdown of glucose by different pathways can be illustrated as follows.
In yeast and human muscle cells, the breakdown of pyruvate occurs in the absence of oxygen whereas in mitochondria, the breakdown of pyruvate occurs in the presence of oxygen.
3. How is oxygen and carbon dioxide transported in human beings?
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Answer
Haemoglobin transports oxygen molecule to all the body cells for cellular respiration. The haemoglobin pigment present in the blood gets attached to four $O_2$ molecules that are obtained from breathing. It thus forms oxyhaemoglobin and the blood becomes oxygenated. This oxygenated blood is then distributed to all the body cells by the heart. After giving away $O_2$ to the body cells, blood takes away $CO_2$ which is the end product of cellular respiration. Now the blood becomes de-oxygenated.
Since haemoglobin pigment has less affinity for $CO 2, CO 2$ is mainly transported in the dissolved form. This de-oxygenated blood gives $CO_2$ to lung alveoli and takes $O_2$ in return.
Transportation of $O_2$ and $CO_2$ in blood
4. How are the lungs designed in human beings to maximise the area for exchange of gases?
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Answer
The exchange of gases takes place between the blood of the capillaries that surround the alveoli and the gases present in the alveoli. Thus, alveoli are the site for exchange of gases. The lungs get filled up with air during the process of inhalation as ribs are lifted up and diaphragm is flattened. The air that is rushed inside the lungs fills the numerous alveoli present in the lungs.
Each lung contains 300-350 million alveoli. These numerous alveoli increase the surface area for gaseous exchange making the process of respiration more efficient.
