Viruses
Viruses are non-living particles that hijack cells.
About this topic
Viruses are tiny particles, much smaller than bacteria, consisting of genetic material (DNA or RNA) in a protein coat, sometimes with an outer envelope. They aren't cells and can't reproduce on their own; they invade a host cell and hijack its machinery to make copies. Most scientists classify them as non-living outside a host.
In the lytic cycle, a virus attaches to specific receptors on a host cell, injects or releases its genetic material, uses the cell to make new viral parts, assembles new viruses and bursts out, killing the cell. Some viruses, like HIV, insert their genes into host DNA and stay hidden for years. Each virus infects only certain hosts, which is why the flu does not infect plants.
Diseases include influenza, colds, measles, COVID-19, HIV/AIDS and the tobacco mosaic virus in plants. Because viruses live inside cells, antibiotics do not work. Treatment relies on antivirals and prevention by vaccines, which have eradicated smallpox.
RNA viruses mutate quickly, which is why a new flu vaccine is needed each year. A common misconception is that viruses are tiny bacteria, but they lack cell structure entirely. Another is that all viruses are harmful; some, called bacteriophages, infect bacteria and are studied as medical tools.
Key ideas
- Protein coat and genetic material
- Lytic and lysogenic cycles
- Antibiotics don't work
Quick check
Use cases: where Viruses helps
- Homework: review the key idea behind Viruses before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Viruses without notes.
- Visual learning: play with the interactive lab to see how Viruses changes when you adjust its inputs.
- Teaching a friend: explain Viruses in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Viruses?
Viruses are non-living particles that hijack cells.
What will I learn in Viruses?
Protein coat and genetic material. Lytic and lysogenic cycles. Antibiotics don't work.
Is Viruses part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Viruses lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Viruses?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.