Problem 5 - Campbell Biology

Question

\begin{equation} \begin{array}{l}{\text { RNA viruses require their own supply of certain enzymes because }} \\ {\text { (A) host cells rapidly destroy the viruses. }} \\\ {\text { (B) host cells lack enzymes that can replicate the viral genome. }} \\ {\text { (C) these enzymes translate viral mRNA into proteins. }} \\\ {\text { (D) these enzymes penetrate host cell membranes. }}\end{array} \end{equation}

Step-by-Step Solution

Answer

Option B: Host cells lack enzymes that can replicate the viral genome.

Step 1: Read the Question Carefully

Understand the question by reading it thoroughly. The question asks why RNA viruses require their own supply of certain enzymes.

Step 2: Analyze the Given Options

Examine each option carefully and think about whether it is a valid reason for RNA viruses to require their own enzymes.- (A) Host cells rapidly destroy the viruses.- (B) Host cells lack enzymes that can replicate the viral genome.- (C) These enzymes translate viral mRNA into proteins.- (D) These enzymes penetrate host cell membranes.

Step 3: Evaluate Option A

Option A states that host cells rapidly destroy the viruses. This doesn't address why the viruses need their own enzymes, rather, it talks about the host response.

Step 4: Evaluate Option B

Option B states that host cells lack enzymes that can replicate the viral genome. RNA viruses need RNA-dependent RNA polymerase to replicate their RNA genome, which host cells typically do not have.

Step 5: Evaluate Option C

Option C states that the enzymes translate viral mRNA into proteins. This doesn't directly address genome replication, which is the specific need mentioned in the context of RNA viruses having their own enzymes.

Step 6: Evaluate Option D

Option D states that these enzymes penetrate host cell membranes. This is not accurate since it doesn't correspond to the genomic replication necessity.

Step 7: Choose the Best Answer

The most accurate explanation is Option B: 'Host cells lack enzymes that can replicate the viral genome.' RNA viruses need their own RNA-dependent RNA polymerase for replication.

Key Concepts

viral replication

Viral replication is the process by which viruses produce copies of themselves within a host cell. This is crucial for the survival and proliferation of viruses. RNA viruses use their RNA as genetic material, which can directly translate into proteins or serve as a template for replication.
To begin replication, the virus first attaches to and enters a host cell. Once inside, it hijacks the host's cellular machinery to create more viral RNA and proteins. This leads to the assembly of new virus particles, which are then released to infect more cells.
These steps ensure the continuous cycle of infection and replication, spreading the virus throughout the host organism.

RNA-dependent RNA polymerase

RNA-dependent RNA polymerase (RdRp) is a critical enzyme used by RNA viruses to replicate their RNA genomes. Host cells usually lack this enzyme because their own genomes are DNA-based, making RdRp essential for the life cycle of RNA viruses.
When an RNA virus infects a host cell, it relies on RdRp to synthesize a complementary RNA strand from its original RNA template. This new strand can either be used to produce viral proteins or to create additional RNA genomes for the formation of new viral particles.
The enzyme ensures that the virus can efficiently reproduce its genetic material, enabling the production of multiple copies within a host cell.

viral enzymes

Viral enzymes are specialized proteins that facilitate various stages of the viral life cycle. These enzymes are often encoded in the viral genome and are synthesized using the host's cellular machinery.
For RNA viruses, critical enzymes include RNA-dependent RNA polymerase, which aids in genome replication, and proteases, which help in processing viral proteins.
Without these enzymes, RNA viruses would be unable to replicate, assemble, and release new viral particles.
This highlights the importance of enzymes in overcoming the limitations of the host cell and ensuring successful virus propagation.

host cell interactions

Interactions between a virus and its host cell are central to the viral replication process. These interactions begin when the virus binds to specific receptors on the surface of the host cell, allowing it to enter the cell.
Once inside, the virus must navigate the host's cellular environment, co-opting the host's machinery to replicate its genome and produce viral proteins.
The host cell's natural defenses can also influence these interactions. For instance, host cells often launch immune responses aimed at destroying the virus. Viral proteins may counteract these defenses, helping the virus to evade immune detection.
Understanding these interactions is key to developing antiviral strategies, as disrupting these processes can prevent the virus from succeeding in its replication efforts.