Which of the following best describes how an organism senses a disturbance in gas levels?

• A. Cells sense gas disturbances only when they physically touch the gas molecules.
• B. Enzymes directly convert gases into energy, which is sensed by the nervous system.
• C. Specialized receptor cells detect changes in gas concentrations and initiate a signaling cascade.
• D. Hormones are released randomly in response to any environmental change, including gas levels.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of gas sensing in organisms. Organisms have specialized receptor cells that detect changes in gas concentrations, such as oxygen (O₂) or carbon dioxide (CO₂). These receptors are often located in specific tissues or organs, such as chemoreceptors in the carotid body for mammals.
2. Step 2: Learn about signaling cascades. When receptor cells detect a change in gas levels, they initiate a signaling cascade. This involves a series of molecular events, such as the activation of proteins, enzymes, or ion channels, which transmit the signal to other parts of the organism.
3. Step 3: Clarify why physical contact with gas molecules is not required. Gas molecules diffuse through membranes and interact with receptor proteins without the need for direct physical contact. This is a passive process based on concentration gradients.
4. Step 4: Address the incorrect statement about enzymes converting gases into energy. Enzymes do not directly convert gases into energy. Instead, gases like oxygen are used in cellular respiration to produce ATP, the energy currency of the cell, but this process is not directly sensed by the nervous system.
5. Step 5: Explain why hormone release is not random. Hormones are released in response to specific stimuli, such as changes in gas levels, but this process is regulated and not random. Hormonal responses are part of a coordinated system to maintain homeostasis.