Prokaryotic and eukaryotic cells compared

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use this

   Two cell cutaways side by side (model drawing, not to scale) above a Venn diagram. Left cutaway: a prokaryotic cell. Right cutaway: a eukaryotic (animal) cell. Venn diagram, left circle, prokaryotic cell only: DNA in a nucleoid; no membrane-bound organelles. Right circle, eukaryotic cell only: DNA inside a nucleus; membrane-bound organelles. Overlap, both cells: plasma membrane; cytoplasm; ribosomes; DNA.

2. 1.

   Bo's friend says a bacterium has no DNA or ribosomes, since it has no nucleus and no organelles. Which response is best?

   • Disagree: a bacterium has DNA in a nucleoid and ribosomes, but no nucleus
   • Agree: ribosomes are organelles, and a bacterium has no organelles
   • Agree: DNA needs a nucleus to be kept in, so a bacterium has no DNA
   • Disagree: a bacterium is a tiny animal cell, so it has a nucleus and organelles
3. 2.

   Two cutaways side by side (model drawing, not to scale). Esme's friend sees a bacterium on a slide and says a bacterium is just a tiny animal. Which response is best?

   • Disagree: a bacterium is a prokaryote with no nucleus, and it is not an animal
   • Agree: a bacterium is an animal cell that is simply much smaller than the others
   • Agree: a bacterium has a flagellum to move, so it is a tiny animal
   • Disagree: a bacterium is not an animal, and it has no DNA

4. Use this

   Mitochondria and bacteria (real data, from OpenStax Biology), 4 rows. Columns: feature, bacterium, mitochondrion. own DNA, yes, in a nucleoid, yes, its own genome; own ribosomes, yes, yes, like those of prokaryotes; membranes around it, one plasma membrane, two; how new ones form, the cell divides, divides by a process like binary fission.

5. 3.

   Kira reads about the idea that mitochondria came from bacteria taken into a larger cell. Which statement does the table best support?

   • Mitochondria have a nucleus of their own, which shows they were cells
   • Mitochondria make energy and bacteria make energy, so they are the same
   • Mitochondria have no DNA, since the nucleus holds the DNA of a eukaryotic cell
   • Mitochondria have their own DNA and ribosomes, as bacteria do

6. Chloroplasts (real data, from OpenStax Biology)

   feature	chloroplast
   own DNA	a circular DNA chromosome
   own ribosomes	similar to those of cyanobacteria
   membranes around it	two
   inner membrane	thought to come from the plasma membrane of a cyanobacterium taken in

7. 4.

   Luz asks why a chloroplast having two membranes fits the idea that chloroplasts came from bacteria taken into a larger cell. What is the best reason?

   • Both membranes came from the nucleus, since a chloroplast has no DNA of its own
   • Two membranes show that the cell built the chloroplast from scratch inside its cytoplasm
   • The inner membrane is thought to come from the plasma membrane of the cyanobacterium
   • Two membranes show chloroplasts came from mitochondria, which also have two

8. How new mitochondria form (real data, from OpenStax Biology)

   observation	result
   where new mitochondria come from	previous mitochondria
   how they divide	by pinching in two like binary fission in prokaryotes
   built from scratch by the cell	no

9. 5.

   Milo reads the card on new mitochondria. Which conclusion fits the evidence?

   • New mitochondria are built from scratch whenever the cell needs energy
   • New mitochondria come from existing ones that divide, much as bacteria divide
   • New mitochondria grow from ribosomes in the cytoplasm
   • New mitochondria are copied from the nucleus's DNA, since they have no DNA of their own
10. 6.

    The side is unknown. Tala knows a model cube cell has a surface area-to-volume ratio of 0.15 per µm. Use the rule. How long is its side?

    • 5.85 µm
    • 0.025 µm
    • 0.9 µm
    • 40 µm
11. 7.

    Zee doubles a model cell's side from 6 µm to 12 µm. Which statement fits the table?

    • Surface area grew from 216 to 864, so the larger cell exchanges better
    • Volume grew 8 times but surface area only 4 times, so the ratio fell from 1 to 0.5
    • Volume and surface area both grew 8 times, so the ratio stayed at 1
    • The bigger cell holds 8 times the materials, so it exchanges 8 times better than before

12. Use this

    Cell card W (model data, not to scale), from a garden-soil sample. It has a cell wall, a plasma membrane, DNA in a central region, ribosomes and a flagellum. It has no nucleus. Width about 3 µm.

13. 8.

    Ren expected an animal cell, since cell W moves with a flagellum, yet it shows no nucleus. Which explanation fits?

    • W is a tiny animal cell whose nucleus is too small to see under a microscope
    • W is a eukaryote, because it has ribosomes and DNA
    • W is a bacterium, a prokaryote, and bacteria can have flagella
    • W is a plant cell, because it has a cell wall
14. 9.

    Cell V has a nucleus and mitochondria. Milo finds that cell V is 4 µm wide, inside the prokaryotic range, yet it has a nucleus and mitochondria. Which explanation fits?

    • V is a prokaryote, because its width fits 0.1 to 5.0 µm
    • V is neither kind of cell, because its size fits one and its parts fit the other
    • V is a eukaryote: a nucleus and organelles decide the type; size ranges are typical
    • The measurement must be wrong, because a cell with a nucleus must be 10 µm or more across
15. 10.

    model data, not to scale. Its inside has not been checked yet. Esme thinks the soil cell is a eukaryote because it might have DNA and ribosomes. Which finding would show it is a prokaryote?

    • It has no DNA of its own, because prokaryotes are cells that lack DNA
    • It has no ribosomes, because prokaryotes are cells that lack ribosomes
    • Its DNA lies in a nucleoid, with no nucleus or organelles with membranes
    • It has a cell wall, because prokaryotes are the cells that have walls