VIRUSES ARE NOT ALIVE BUT AFFECT LIVING
THINGS
VIRUSES SHARE SOME CHARACTERISTICS WITH
LIVING THINGS• VIRUSES MULTIPLY INSIDE LIVING
CELLS
• VIRUSES MAY HARM HOST CELLS
VIRUSES• VIRUS means poison; much smaller than bacteria,
can’t even be “filtered” out of a liquid like bacteria can be.
• Viruses have genetic material inside of a protective protein coat called a CAPSID.
• They come in many shapes & sizes, but all have a CAPSID and GENETIC MATERIAL.
• VIRUSES must use a host cell to reproduce (by making genetic material & capsids).
• Viruses do not grow & don’t respond to changes in the environment, so they are not living organisms
Viruses Multiply inside Living Cells• Viruses use HOST CELLS to make copies of themselves. A
bacteriophage (means bacteria eater) is used to show the process.• ATTACHMENT: virus attaches to cell • INJECTION: injects its DNA inside• PRODUCTION: uses cell’s machinery to copy the viral DNA and
capsids• ASSEMBLY: viral DNA forces infected cell to assemble new
viruses• RELEASE: cell bursts open, releasing 100+ new viruses to infect
other cells.• Viruses have proteins on surface that look like proteins the host
cell normally needs to fool it & “dock” onto sites of cell membrane
Viruses May Harm Host Cells• Virus uses cell’s material, energy , and processes to
reproduce often bursting out & destroying the host cell. (some just hide in cell or just make 1 virus at a time & not be as harmful)
• About 25 million people died of influenza virus in outbreak after WWI.
• Plant viruses can stunt growth & kill plants• Plant, animals, bacteria & all other living things can be
infected by viruses.• Scientists can use viruses to insert pieces of genetic
material into living cells. (like a marine organisms DNA into other tissue causing it to glow so can study it better)
