Viruses compared with cells, and how viruses spread

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use this

   Fact card (CDC, paraphrased). Antibiotics are medicines for certain infections caused by bacteria. A virus is a different kind of germ from a bacterium. Antibiotics do not work on viruses, such as the ones behind colds and flu.

2. 1.

   Zee's friend says an antibiotic should work on a cold virus, because antibiotics act on germs. Which response agrees with the fact card?

   • Agree: antibiotics act on germs, and a virus is a germ, so they work on it
   • Agree: a cold virus is a very small bacterium, so an antibiotic acts on it
   • Disagree: antibiotics are for bacteria, and a virus is a different kind of germ
   • Disagree: an antibiotic acts on germs, but a cold virus is too small for it to reach

3. Use this

   Host table (model data), 3 rows. Columns: virus, attaches to cells with. phage T, receptor R, found on certain bacteria; plant virus V, receptor S, found on cells of one kind of plant; virus M, receptor U, found on certain animal cells.

4. 2.

   Ari's friend says phage T could infect human cells, because every cell has a plasma membrane. Which response uses the table?

   • Disagree: phage T needs receptor R, which is found on certain bacteria
   • Disagree: phage T is far too large to fit inside a human cell, whatever its receptors
   • Agree: having a plasma membrane is enough for a virus to attach to a cell
   • Agree: a virus copies itself in any cell it manages to enter, even a human cell
5. 3.

   Drug W stops a cell from building its cell wall. Ren reads that drug W stops cells from building a cell wall. Using the table, why does drug W have no target in a virus particle?

   • The drug does act on a virus, by stopping it from building a capsid
   • A virus particle has no cell wall for the drug to act on
   • A virus has a cell wall, but it is built inside the host cell
   • A virus particle is too small for the drug to reach

6. Drug table (model data)

   drug	what it blocks	found in healthy host cells
   W	building a bacterial cell wall	no
   X	a protein made only by the virus	no
   Y	a protein that host cells need	yes

7. 4.

   Luz reads a drug table. Which drug could slow a virus while sparing host cells?

   • Drug W, because a virus must build a cell wall to copy itself
   • Drug Y, because a protein that host cells need is a safe target
   • No drug can slow a virus, because a virus has nothing that a drug can block
   • Drug X, because its target is a viral protein that host cells lack

8. Comparison table (model data, from OpenStax Biology 2e)

   germ	who does most of the copying work
   bacterium	its own ribosomes and enzymes
   virus	the host cell's ribosomes and enzymes

9. 5.

   Milo asks why a drug against a virus is harder to design than a drug against a bacterium. Which explanation fits the table?

   • A virus has no genetic material for a drug to reach, so it cannot be blocked
   • A virus copies itself outside cells, where no drug can enter or reach it
   • A virus has its own ribosomes, and they are the same as the host cell's ribosomes
   • A virus uses host-cell machinery, so a drug aimed at it could harm host cells

10. Model data for phage P

    time in minutes	bacteria in the dish	free phage particles
    0	1,000	0
    30	1,000	0
    60	100	9,000

11. 6.

    Bo reads model data from a dish of bacteria with phage P. Which cycle do the data best fit?

    • Neither cycle, because free phage particles copy themselves in the dish
    • Lytic cycle, because the number of bacteria stayed the same
    • Lysogenic cycle, because the phage DNA is hidden in the bacteria
    • Lytic cycle, because bacteria fell while free phage particles rose
12. 7.

    Each time a bacterium divides, its prophage is copied into both new cells. Esme reads model data on bacteria that carry a prophage. If the pattern continues, how many bacteria carry the prophage after 5 divisions?

    • 10
    • 25
    • 32
    • 64
13. 8.

    Noah notices that an enveloped virus is wrapped in a membrane. Does the envelope make the virus a cell?

    • Yes: the envelope is a plasma membrane that the virus makes itself
    • No: the envelope is host-cell membrane, and the virus has no ribosomes
    • No: the envelope lets the virus attach to any cell it meets and enter it
    • Yes: anything wrapped in a membrane is a cell, whatever else it lacks
14. 9.

    1 µm = 1,000 nm. Jun sees that a giant virion is wider than a small bacterium. What does this show?

    • Width does not decide: a virion lacks cell structure however wide it is
    • The giant virion is a bacterium, because it carries genetic material
    • The table is wrong, because virions are narrower than bacteria
    • The giant virion is a cell, because it is wider than any small bacterium

15. Lab notebook (model data)

    sample	what is seen after 1 day
    phage sample alone in a clean dish	no new phage particles
    bacteria alone in broth	more bacteria and no phage particles
    phage sample added to bacteria in broth	many new phage particles

16. 10.

    Pia reads a lab notebook about a phage sample. Which statement explains what the notebook shows?

    • A phage divides in two on its own, but slowly in a clean dish
    • A phage has its own ribosomes, so it copies itself in any dish
    • A phage copies itself only inside a host cell, so it needs the bacteria
    • The bacteria are bystanders, since a phage copies itself in whatever cell is near