Biology Pak 9 Self Check Quiz 3

The correct answer is "All of the above." Viruses are not considered alive because they lack cellular structure, which is a defining characteristic of living organisms. Additionally, viruses cannot use energy on their own or produce proteins, both of which are essential processes for life. Therefore, all of the given reasons contribute to the understanding that viruses are not alive.

The correct answer is lytic cycle. The lytic cycle refers to the cycle of viral infection, replication, and cell destruction. In this cycle, the virus attaches to the host cell, injects its genetic material, takes over the cell's machinery to produce more viral particles, and eventually causes the cell to burst, releasing the newly formed viruses. This cycle is characterized by the destruction of the infected cell and the release of viral progeny.

The capsid of a virus refers to its protective outer coat. This coat helps to shield the genetic material of the virus, such as its DNA or RNA, from damage and degradation. It also plays a crucial role in the virus's ability to infect host cells. The capsid is made up of protein subunits called capsomeres, which come together to form a symmetrical structure around the viral genome. The protective outer coat allows the virus to survive in various environments and facilitates its entry into host cells during infection.

Nitrogen-fixing bacteria have the ability to convert atmospheric nitrogen into ammonia. This process is known as nitrogen fixation and is essential for plants, particularly legumes, to obtain the nitrogen they need for growth. The bacteria form a symbiotic relationship with the plant, colonizing their roots and converting the nitrogen gas in the air into a form that the plants can use. This conversion of atmospheric nitrogen into ammonia is a crucial step in the nitrogen cycle and helps to maintain the availability of nitrogen in the soil for plant growth.

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HIV is a virus that infects and attacks the immune system, not the circulatory system. It can be transmitted to infants during pregnancy or through breast milk, so the statement that HIV cannot be transmitted to infants in this way is false. However, the glycoproteins on HIV do enable it to bind with receptors and co-receptors on host cells, allowing it to enter and infect these cells. Currently, there is no vaccine available to protect people from getting HIV.

Eukaryotic cells have nuclei, membrane-bound organelles, and linear chromosomes, whereas bacterial cells do not have any of these structures. Bacterial cells have a simpler structure and lack a true nucleus, membrane-bound organelles, and linear chromosomes.