
Concept explainers
Figure 17.5 Which of the following statements about virus structure is true?
a. All viruses are encased in a viral membrane.
b. The capsomere is made up of small protein subunits called capsids.
c. DNA is the genetic material in all viruses.
d. Glycoproteins help the virus attach to the host cell.

Introduction:
Viruses have diversity in terms of the structure, the method of replication, host and target cells. Viruses are non-cellular and parasitic and do not have any internal organelles, metabolic process or plasma membrane. The virion consists of a nucleic acid core of either DNA or RNA, an outer coating of protein, or sometimes may have an outer membrane which is made up of phospholipid membrane which is derived from the host cell and proteins.
Answer to Problem 1ACQ
Correct answer:
The correct answer is option (d) Glycoproteins help the virus attach to the host cell.
Explanation of Solution
Explanation/justification for the correct answer:
Option (d) Glycoproteins help the virus attach to the host cell. All the virions have the nucleic acid genome which is covered with an outer protein protective layer is termed as capsid. Capsomere is small protein subunits that make up the capsid. The capsid of some of the viruses has a surrounding outer structure which is the viral envelope.
All the viruses contain some kind of the glycoprotein for attachment to the host cell molecules which are the viral receptors. These cell surface molecules are exploited by viruses for recognition and infection to particular types of cell. So, the correct answer is option (d).
Explanation for the incorrect answer:
Option (a) All viruses are encased in a viral membrane. Viruses may or may not have a viral membrane. So, this is an incorrect option.
Option (b) The capsomere is made up of small protein subunits called capsids Capsomere are small protein subunits that make up the capsid. So, this is an incorrect answer.
Option (c) DNA is the genetic material in all viruses. The virion consists of a nucleic acid core of either DNA or RNA. So, this is an incorrect answer.
All the viruses contain some kind of the glycoprotein for attachment to the host cell molecules which are the viral receptors. These cell surface molecules are exploited by viruses for recognition and infection to particular types of cell. Hence, the correct answer is option (d) Glycoproteins help the virus attach to the host cell.
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