The virus that causes bird flu can attach to the cells of the lower part of the respiratory system in humans, but not to the cells of the upper part of the respiratory system. The most likely reason for this is that these two groups of cells have different
(1) DNA codes in their nuclei (2) enzymes in their mitochondria (3) amounts of water in their cytoplasm (4) receptor molecules on their membranes
Answer and Explanation:
A virus is a very small infectious particle that can only replicate inside the host. The main goal of the virus is to get inside the cell so it can start replicating. Why can a virus in this question attach to cells of the respiratory system but not of the upper part of respiratory system? The reason must be the receptor molecules on their membrane, choice 4. A virus has molecules on it's membrane that can recognize and attach to the specific molecules of host cells. Therefore, only cells with specific receptor molecules will be able to be targeted by the virus.
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