Biology · Rung 3 of 9

Viruses, bacteria and contagion

A virus is not a cell and cannot copy itself without getting inside one; a bacterium is a complete cell that divides on its own; a fungus is eukaryotic like you, which is why attacking it without harming you is hard. The practical part follows: an antibiotic attacks things only bacteria have, such as their wall, so against a virus it does absolutely nothing. Flu and colds are viruses. A contagion is a chain — someone releases it, it survives a while outside, it enters another, it multiplies — and breaking any link will do. And antibiotic resistance is natural selection at full speed inside your body: the drug kills the weak bacteria and clears space for those that endured, so what becomes resistant is the bacterium and not the person.

Where this sits

Opens up
The body's defences

Exercises from this rung

Generated by the app, from easiest to hardest

  1. What sets a fungus apart?

    • is a whole animal living inside another
    • is eukaryotic, like you, which is why attacking it without harming you is harder
    • is the only one here that is not a cell: it cannot copy itself without getting inside one
    • is a complete cell that divides on its own

    Why That it is eukaryotic, like you, which is why attacking it without harming you is harder. The difference is not size but what they are, and the practical consequence follows: an antibiotic attacks things only bacteria have, so **against a virus it does absolutely nothing**. Taking one for a cold does not shorten the cold and does train your bacteria.

    easier

  2. What does an antibiotic work against?

    • Against bacteria and nothing else
    • Against fever, whatever causes it
    • Against any infection, of whatever kind
    • Against viruses, especially flu

    Why Only against bacteria. It works by attacking things a bacterium has and your cells do not, such as its wall: that is how it cures you without killing you. A virus has none of that, so the antibiotic walks straight past it. And flu and colds are viruses, which is exactly where they are most over-prescribed.

    in between

  3. How does an antibiotic-resistant bacterium appear?

    • The body of whoever takes it becomes resistant
    • Bacteria get used to the drug with use
    • The drug loses strength while it is stored
    • The ones that survive the treatment stay and multiply

    Why It is natural selection at full speed, inside your own body. Among millions of bacteria some happen to carry a variant that survives; the antibiotic kills the rest and leaves it the space. **What becomes resistant is the bacterium, not the person**, and that is why stopping treatment halfway is the worst move: it kills the weak ones and leaves alive exactly those that endure.

    harder