Remember! Viruses are not living organisms because they are incapable of carrying out all life processes. Viruses are not made of cells can not reproduce on their own do not grow or undergo division do not transform energy lack machinery for protein synthesis
How are the structures similar? How are they different?
Why are viruses so specific? All viruses contain the same major parts (capsid & genetic material), but each virus is specific to a specific type of cell! Why are viruses so specific?
Viral Structure
If viruses aren’t made of cells, then what are they made of? All viruses have: Nucleic Acids Genetic material (DNA or RNA) Capsid Protein coat Determines shape & infection process Houses nucleic acids capsid envelope
The Viral Capsid The capsid provides protection for viral nucleic acid & provides a way for the virus to enter a host cell. nucleic acid capsomere capsid
What type of nucleic acids do viruses use? DNA RNA Can be DNA or RNA Protein
DNA RNA
Which do you think is the smallest? A. Genome of Eukaryotes B. Genome of Prokaryotes (bacteria) C. Genome of Viruses D. What’s a genome? Genome of Viruses! Viruses contain much less genetic information than cells!
What is one function of the viral capsid? Produce toxins Dig into cell membranes Protect the nucleic acid Make proteins Protect the nucleic acid, which will be either DNA or RNA!
Viral Shapes Determined by the capsid
Helical Polyhedral Spherical Bacteriophage
Which type of cells do bacteriophages infect? Immune Cells Phage Cells Viral Cells Prokaryotic Cells Prokaryotic Cells (bacteria)!
The name tells you that this virus infects bacteria!
What are the effects of being infected by this virus? You will get AIDS. You will get the flu. You will get a cold sore. You will get the Bubonic Plague. Influenza virus causes the flu!
This name tells you that this virus causes influenza (the flu)!
A cell’s membrane won’t let just any ol’ particle in, so why do cells allow viruses to infect them? They have no choice! Viruses mimic molecules a host cell wants & needs to take in. Viruses “trick” the host cell into letting the virus in!
Influenza infecting a host cell Viral Attachment Viruses have special proteins called receptors that stick out of their capsid & match with receptor proteins on a cell membrane. Remember that viruses are species-specific! Sometimes they only infect a single cell type within a single species. Influenza infecting a host cell
Which type of cell would be infected by this virus? The brain cell! Compare the proteins on the surface of the cell and the virus. They match like puzzle pieces! A B C D
Remember! Viruses are specific! This is due to the receptor proteins needing to match with the cell’s receptor proteins.
Which cell does each virus infect? Read the short Virus Reading before beginning. With your groups, match each virus to the cell that it infects. Make predictions, and I’ll show the answer later.