Eukaryotes and prokaryotes: location of genetic material
مُقدَّم| English | المعنى |
|---|---|
| plasmid/ˈplæzmɪd/ | بلازميد |
| prokaryote/ˈprɒkərɪəʊt/ | بدائيات النواة |
What would explain this observation?
- A bacterium and a plant cell both contain DNA. Their genetic material is arranged differently, and a bacterium is usually much smaller.
Build the model
- Plant and animal cells are eukaryotic: their genetic material is enclosed in a nucleus.
- A bacterial cell is prokaryotic and has no nucleus.
- It contains cytoplasm, a cell membrane and a surrounding cell wall.
- Its main genetic material is a single DNA loop, and it may also contain small DNA rings called plasmids 质粒.
- prokaryote 原核生物: An organism whose cells lack a nucleus enclosing the main genetic material.
- plasmid: A small DNA ring that can occur in a bacterial cell.
Which observation supports identifying the model as a bacterial cell?
الصعوبة 1/5 · 100 عملة + مكافأة صغيرة عند الإكمال الأول اليوم
Bacteria are prokaryotes: their genetic material is a main DNA loop lying free in the cytoplasm with no nucleus around it. A nucleus enclosing chromosomes marks a eukaryote, and a cellulose wall belongs to plants.
Match each technical term to its precise meaning.
الصعوبة 2/5 · 140 عملة + مكافأة صغيرة عند الإكمال الأول اليوم
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Use structures rather than size alone to identify a cell type.
- A plant cell has a cellulose cell wall, but a bacterial wall is not made of cellulose.
- Not every bacterium has a plasmid.
- A small cell image can be enlarged, so image size cannot by itself show real cell size.
In the lab: Inspect teacher-provided labelled images with scale bars. For a size comparison, convert both real dimensions into one unit before dividing. One millimetre is 1,000 micrometres; one micrometre is 1,000 nanometres. State whether the ratio concerns length, area or volume.
Which two habits make the investigation or model in this case more defensible?
الصعوبة 2/5 · 140 عملة + مكافأة صغيرة عند الإكمال الأول اليوم
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: a bacterial cell is 2 micrometres long and a plant cell is 40 micrometres long.
- Length ratio = 40/2 = 20.
- In metres these are 2×10⁻⁶ m and 4×10⁻⁵ m.
- The plant cell is twenty times longer in this example, not twenty times larger in every possible measure.
Your turn: A 30 micrometre plant cell is compared with a 3 micrometre bacterial cell. Find the length ratio plant/bacterium.
A 30 micrometre plant cell is compared with a 3 micrometre bacterial cell. Find the length ratio plant/bacterium.
الصعوبة 2/5 · 140 عملة + مكافأة صغيرة عند الإكمال الأول اليوم
The result is 10 . Known: plant cell 30 micrometres; bacterial cell 3 micrometres. Length ratio = 30/3 = 10. The plant cell is ten times longer in this example - a length comparison, not a volume or complexity claim.
Check the conclusion and its limits
- Prokaryotes have DNA even though they lack a nucleus.
- Magnification changes the displayed size; it does not turn one cell type into another.
- Order-of-magnitude estimates give a scale comparison rather than a precise identity test.
Not true: A bacterial cell has no genetic material because it has no nucleus. Prokaryotes have no nucleus, but their DNA is present as a loop in the cytoplasm plus smaller plasmids. No nucleus does not mean no genetic material.
- Plant and animal cells are eukaryotic: their genetic material is enclosed in a nucleus.
- Use structures rather than size alone to identify a cell type.
- Watch for: prokaryotes have DNA even though they lack a nucleus.
Prokaryotes have no nucleus, but their DNA is present as a loop in the cytoplasm plus smaller plasmids.
الصعوبة 1/5 · 100 عملة + مكافأة صغيرة عند الإكمال الأول اليوم
True. Prokaryotes have no nucleus, but their DNA is present as a loop in the cytoplasm plus smaller plasmids. No nucleus does not mean no genetic material.
An organism whose cells lack a nucleus enclosing the main genetic material: write the technical term.
الصعوبة 1/5 · 100 عملة + مكافأة صغيرة عند الإكمال الأول اليوم
prokaryote means An organism whose cells lack a nucleus enclosing the main genetic material.