Which of the following is/are always true?
a. Viruses cannot reproduce outside a host cell
b. Viruses are not surrounded by a membrane
c. Viruses are not made up of cells
d. A and C are correct
e. A, B, and C are correct

Verified step by step guidance

1. Step 1: Understand the nature of viruses. Viruses are acellular entities, meaning they are not made up of cells. This is a fundamental characteristic that distinguishes them from living organisms like bacteria, plants, and animals.
2. Step 2: Analyze the statement in option (a). Viruses cannot reproduce on their own and require a host cell to replicate. This is because they lack the cellular machinery (e.g., ribosomes, enzymes) necessary for independent reproduction.
3. Step 3: Evaluate the statement in option (b). Viruses are not surrounded by a membrane. Instead, they are typically composed of a protein coat (capsid) that encloses their genetic material, and some viruses may have an additional lipid envelope derived from the host cell membrane.
4. Step 4: Combine the information from steps 1, 2, and 3 to assess option (d). Option (d) states that both (a) and (c) are correct. Since both statements are true, this option is valid.
5. Step 5: Assess option (e), which claims that (a), (b), and (c) are all correct. Since all three statements are consistent with the characteristics of viruses, this option is also valid. Compare this with the other options to determine the most comprehensive answer.

Key Concepts

Virus Reproduction

Viruses are unique biological entities that cannot reproduce independently; they require a host cell to replicate. Once inside a host, they hijack the cellular machinery to produce new viral particles, which is essential for their life cycle. This characteristic distinguishes them from living organisms, which can reproduce on their own.

Viral Structure

Viruses are composed of genetic material (either DNA or RNA) encased in a protein coat called a capsid. Unlike cells, they lack a cellular structure and are not surrounded by a membrane. This structural simplicity is a key feature that defines viruses and differentiates them from cellular life forms.

Cell Theory

Cell theory is a fundamental principle in biology stating that all living organisms are composed of cells, which are the basic units of life. Viruses do not fit this definition as they are acellular and do not possess the characteristics of living cells, such as metabolism or cellular organization. This distinction is crucial for understanding the nature of viruses.