Lyrapettigrew
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Hello, recently I have been revising some material regarding viruses and how they differ to other cells. I found some questions online but i am struggling to understand how to answer them. I have attempted a few solutions but feel that I would tremendously benefit from some further help and explanation.

Rhinoviruses cause the common cold, in actuality, the common cold is caused by a variety of viruses. The stages in which the cold virus attacks the cells on the inside of a human nose are as follows;
Stage 1: Virus attaches to protein receptor on host cell membrane.
Stage 2: RNA of virus is released in to cell as protein capsid is lost.
Stage 3: RNA read at ribosome forming three enzymes, (D, F and G)
Stage 4: New viruses formed using enzymes D and F
Stage 5: Viruses released as host cell membrane deteriorates as the result of the action of enzyme G

Question 1: Why do common cold viruses not result in symptoms if they enter through the blood via a laceration to the skin?

I believe that this is because viruses are only able to infect the cells of one species of hosts, or group of related species, and only one type of specific cells within the host. In the case of the rhinoviruses, or colloquially the common cold, the viruses are only able to invade the nose cells of human beings, not other human cells or the noses of other species.
The molecular basis for this specificity is that a particular surface molecule, called the viral receptor, must be located on the host cell surface for the virus to attach. Moreover, metabolic differences in different cell types based upon differential gene expression are a factor in which cells a virus may use to replicate. It is imperative that the cell is manufacturing the substances the virus requires, for example enzymes the virus genome itself does not have genes for, or the virus will not be able to replicate using that cell, here being the nose cells.

Question 2:

a) Suggest why the enzymes D and F are required in stage 4?

Well, looking at the different stages as the virus attacks I assume that the question is outlining the lytic cycle i.e:
Stage 1 and 2= Entry; the nucleic acid of the virus enters the host cell
Stage 3 = Synthesis; the viral nucleic acid utilises the host cell's ribosomes materials and energy to produce new proteins and nucleic acid molecules
Stage 4 = Assembly; new viruses are assembled from the host cell
Stage 5 = Release ; the virus are released from the host cell as the cell membrane lyses to release them.

So to actually answer the question, the enzymes D and F I believe are produced when the DNA polymerase belonging to the host cell transcribes the viral genes to make mRNA.
Or would these enzymes be representative of DNA helicase and DNA polymerase of the host cell? In which case these enzymes are required firstly to overcome the hydrogen bonds of the polynucleotide strands to unwind the host cell double helix and secondly to catalyse the formation of the phosphodiester bonds of a molecule of mRNA. New viral RNA is also produced by DNA replication using the host cell's DNA polymerase.

b) How does enzyme G catalyse the breakdown of the host cell membrane in stage 5?

I am really uncertain how to answer. Is the question asking specifically about the enzyme and how it breaks bonds or would it be querying the conditions of the deterioration?

c) Compare the action of RNA in the common cold with that found in HIV.

The action of RNA in HIV is different to the common cold in that it is more complex. In the host cell the enzyme reverse transcriptase produces double stranded DNA from the viral RNA, which may then enter the nucleus and integrate with the host cell DNA exhibiting proviral latency. Its presence would now be undetected. Eventually , or immediately, this DNA will undergo translation to produce new viral proteins and RNA. In contrast, the common cold RNA does not appear to become latent, opting to immediately translate new viral proteins and RNA.

Question 3:

Describe the differences between the genetic material of bacteria and viruses.
I do not think that I can explicitly state two differences between them, I understand that the genetic material of viruses is a core of nucleic acid, being RNA or DNA, while bacteria possess a single, circular DNA molecule in their cytoplasm called a nucleoid.

Would the differences be:
1. The nucleic acid of viruses can be single or double stranded whereas the bacterial nucleoid can only be single stranded
2. The gentic material of bacteria is suspended in the cell's cytoplasm, which viruses lack amongst other organelles.
I do no think that this is correct but I am trying to figure it out 😂
Honestly, I am very confused as to how to appropriately answer these questions and have provided rather half-hearted and confused solutions so I would be highly appreciative of any assistance and explanation 👍
Last edited by Lyrapettigrew; 4 weeks ago
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Lyrapettigrew
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#2
Report Thread starter 3 weeks ago
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(Original post by Lyrapettigrew)
Hello, recently I have been revising some material regarding viruses and how they differ to other cells. I found some questions online but i am struggling to understand how to answer them. I have attempted a few solutions but feel that I would tremendously benefit from some further help and explanation.

Rhinoviruses cause the common cold, in actuality, the common cold is caused by a variety of viruses. The stages in which the cold virus attacks the cells on the inside of a human nose are as follows;
Stage 1: Virus attaches to protein receptor on host cell membrane.
Stage 2: RNA of virus is released in to cell as protein capsid is lost.
Stage 3: RNA read at ribosome forming three enzymes, (D, F and G)
Stage 4: New viruses formed using enzymes D and F
Stage 5: Viruses released as host cell membrane deteriorates as the result of the action of enzyme G

Question 1: Why do common cold viruses not result in symptoms if they enter through the blood via a laceration to the skin?

I believe that this is because viruses are only able to infect the cells of one species of hosts, or group of related species, and only one type of specific cells within the host. In the case of the rhinoviruses, or colloquially the common cold, the viruses are only able to invade the nose cells of human beings, not other human cells or the noses of other species.
The molecular basis for this specificity is that a particular surface molecule, called the viral receptor, must be located on the host cell surface for the virus to attach. Moreover, metabolic differences in different cell types based upon differential gene expression are a factor in which cells a virus may use to replicate. It is imperative that the cell is manufacturing the substances the virus requires, for example enzymes the virus genome itself does not have genes for, or the virus will not be able to replicate using that cell, here being the nose cells.

Question 2:

a) Suggest why the enzymes D and F are required in stage 4?

Well, looking at the different stages as the virus attacks I assume that the question is outlining the lytic cycle i.e:
Stage 1 and 2= Entry; the nucleic acid of the virus enters the host cell
Stage 3 = Synthesis; the viral nucleic acid utilises the host cell's ribosomes materials and energy to produce new proteins and nucleic acid molecules
Stage 4 = Assembly; new viruses are assembled from the host cell
Stage 5 = Release ; the virus are released from the host cell as the cell membrane lyses to release them.

So to actually answer the question, the enzymes D and F I believe are produced when the DNA polymerase belonging to the host cell transcribes the viral genes to make mRNA.
Or would these enzymes be representative of DNA helicase and DNA polymerase of the host cell? In which case these enzymes are required firstly to overcome the hydrogen bonds of the polynucleotide strands to unwind the host cell double helix and secondly to catalyse the formation of the phosphodiester bonds of a molecule of mRNA. New viral RNA is also produced by DNA replication using the host cell's DNA polymerase.

b) How does enzyme G catalyse the breakdown of the host cell membrane in stage 5?

I am really uncertain how to answer. Is the question asking specifically about the enzyme and how it breaks bonds or would it be querying the conditions of the deterioration?

c) Compare the action of RNA in the common cold with that found in HIV.

The action of RNA in HIV is different to the common cold in that it is more complex. In the host cell the enzyme reverse transcriptase produces double stranded DNA from the viral RNA, which may then enter the nucleus and integrate with the host cell DNA exhibiting proviral latency. Its presence would now be undetected. Eventually , or immediately, this DNA will undergo translation to produce new viral proteins and RNA. In contrast, the common cold RNA does not appear to become latent, opting to immediately translate new viral proteins and RNA.

Question 3:

Describe the differences between the genetic material of bacteria and viruses.
I do not think that I can explicitly state two differences between them, I understand that the genetic material of viruses is a core of nucleic acid, being RNA or DNA, while bacteria possess a single, circular DNA molecule in their cytoplasm called a nucleoid.

Would the differences be:
1. The nucleic acid of viruses can be single or double stranded whereas the bacterial nucleoid can only be single stranded
2. The gentic material of bacteria is suspended in the cell's cytoplasm, which viruses lack amongst other organelles.
I do no think that this is correct but I am trying to figure it out 😂
Honestly, I am very confused as to how to appropriately answer these questions and have provided rather half-hearted and confused solutions so I would be highly appreciative of any assistance and explanation 👍
Still no replies 😔 If anyone could offer some advice I am still confused regarding the above question ✌️
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