Viruses

What is the typical size range of viruses compared to cells?

Viruses are typically much smaller than cells, ranging from 20 nm to 300 nm, while cells are generally 1 µm or larger.

What structural elements are present in viruses?

Viruses have a protein coat (capsid), nucleic acid (RNA or DNA), and sometimes an envelope made of lipids.

What structural elements are absent in viruses that are present in cells?

Viruses lack cellular structures such as organelles or metabolic machinery.

What are the core components present in all viruses?

All viruses have nucleotide genomes (DNA or RNA) and protein capsids.

What is the function of a protein capsid in viruses?

The protein capsid serves as protection for the genetic material of the virus.

What type of envelope do some viruses have?

Some viruses have a phospholipid envelope, while non-enveloped viruses lack this structure.

What is the lytic cycle in viral reproduction?

In the lytic cycle, a phage attaches to a host, injects genetic material, replicates using host machinery, assembles new phages, and lyses the host cell to release new phages.

What distinguishes the lysogenic cycle from the lytic cycle?

In the lysogenic cycle, a phage integrates its DNA into the host's genome and replicates without causing immediate lysis.

How do enveloped animal viruses enter host cells?

Enveloped animal viruses enter host cells via fusion with the cell membrane or receptor-mediated endocytosis.

What is a key feature of retroviruses compared to other viruses?

Retroviruses contain RNA genomes and replicate through a DNA intermediate via reverse transcription.

What are the major ways to differentiate viral genomes?

Viral genomes can be differentiated by type of nucleic acid (RNA vs. DNA), genome structure (circular vs. linear), size, and presence of additional features like segmented genomes.