Concept explainers
The Boundaries of Life
If viruses aren't a form of life, what are they? A virus by itself is an inert particle that doesn't approach the complexity of a cell. The simplest virus, such as that causing smallpox (FIG. 1.14), consists of a protein coat that surrounds genetic material. The uncomplicated structure of viruses, coupled with amazing advances in
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Biology: Life on Earth with Physiology (11th Edition)
- Are viruses living? Why or why not?arrow_forwardTRUE/FALSEAll viruses are unable to resist the proteolytic activity (or digestive ordeal) once they are inside our cell organelles called proteasomes and lysosomes. True or False: The presence of at least one membrane is required for any organism to be considered alive.arrow_forwardViruses display many of the characteristics of living organisms. In particular, they reproduce, creating new virus particles. During reproduction, viruses make copies of their genetic material, and some of the copies contain mutations that are beneficial to the virus. For example, HIV (human immunodeficiency virus), the virus that causes the disease AIDS (acquired immunodeficiency syndrome) mutates so often that its surface proteins change faster than we can develop antiviral drugs. New drug-resistant strains of HIV are appearing constantly. However, viruses can reproduce only after entering a living cell of an organism, because viruses hijack the cell’s machinery and use it to produce new viruses. Where does that combination of characteristics place viruses on the scale of nonlife to life? Are viruses living organisms? Nonliving? If neither of those categories fits the properties of viruses, how should they be classified?arrow_forward
- O O O A new virus is discovered. Its RNA genome encodes several proteins, including a reverse transcriptase enzyme. What can you conclude about replication of this virus? Its replication involves a double-stranded RNA intermediate Its replication involves a DNA copy of its genome Its replication depends entirely on cellular enzymes Its replication is entirely independent of cellular enzymes 00 A deficiency in Base Excision Repair (BER) would primarily sensitize you to mutations caused by radiation, X-rays O Chemicals in smoke, and UV radiation O Unavoidable, spontaneously occurring DNA damagearrow_forwardWRITE ABOUT A THEME: ORGANIZATION While virusesare considered by most scientists to be nonliving, they doshow some characteristics of life, including the correlationof structure and function. In a short essay (100–150 words),discuss how the structure of a virus correlates with its function.arrow_forwardDifferent types of viruses have different types of genomes- some are double-stranded DNA, some are single-stranded DNA, some are double-stranded RNA, and some are single-stranded RNA. The Ebola virus genome is a piece of single-stranded RNA. Given this piece of information, do you expect it to see %Adenine = %Uracil and the %Guanine = %Cytosine? Why or why not?arrow_forward
- All HPV are non-enveloped double stranded DNA viruses. Their genomes are circular and approximately 8 kilobase pairs in size. Most encode eight major proteins, 6 located in the “early” region and 2 in the “late” region. The “early” proteins are regulatory in function.... Can you please elaborate about the HPV genome in more detail that what I posted above? Thanks.arrow_forwardThe cell is the basic unit of all living things, and viruses which are generally not considered living but have the ability to infect cells. Describe how the structure of a virus compares to the structure of a cell. You should explain (not list) at least two similarities and two differences between features of cells and viruses including a brief explanation of the function of those structures. Explain why viruses need cells.arrow_forwardAre viruses considered as cells? why or why not?arrow_forward
- Why are viruses are not regarded as true living cells?arrow_forwardAll virus particles, in their infectious form, contain which of the following components? Choose all that apply. Group of answer choices Ribosomes Mitochondria Nuclei Cell membranes Nucleic acids encoding genes Protein capsidsarrow_forwardAs a general rule, viruses are not considered to be alive based on several reasons. One such reason is that some viruses use RNA as their genetic material instead of DNA. Which of the five biological themes does this violate? Briefly explain why.arrow_forward
- Biology Today and Tomorrow without Physiology (Mi...BiologyISBN:9781305117396Author:Cecie Starr, Christine Evers, Lisa StarrPublisher:Cengage LearningBiology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning