Gateways of the nucleus
Pores let things pass; the nucleolus makes ribosome parts.
A walled workshop
The nucleus is wrapped in a covering. Yet materials must go in and out.
How could materials cross the nuclear covering?
What this lesson covers
The idea
The nucleus has a double-layered nuclear membrane with pores for transfer of material to and from the cytoplasm; its nucleolus makes ribosomal subunits, which pass to the cytoplasm and assemble into ribosomes.
A walled workshop
The nucleus is wrapped in a covering. Yet materials must go in and out.
How could materials cross the nuclear covering?
- Through pores in the covering
- They cannot cross at all
- The nucleus has no covering
Follow the subunits
Press + to move through the steps.
Membrane with pores, and a nucleolus
The nucleus has a double-layered nuclear membrane with pores that allow the transfer of material between the nucleus and the cytoplasm. The nucleolus is the dense round body where ribosomal subunits are made. They exit to the cytoplasm, where one large and one small subunit assemble to form a ribosome.
Ribosomes are the protein factories you will meet soon.
- Part | Job
- Nuclear membrane (double layer) | wraps the nucleus
- Pores | let material cross
- Nucleolus | makes ribosomal subunits
- Large + small subunit | assemble into a ribosome in the cytoplasm
Notes
The nucleus has a double-layered membrane with pores. The nucleolus makes ribosomal subunits that leave and assemble (one large, one small) into a ribosome.
Check yourself
The pores in the nuclear membrane…
Where are ribosomal subunits made?
A ribosome forms from…
The nuclear membrane is…
- allow material to move between the nucleus and cytoplasm — correct. Yes.
- let the whole nucleus leave. Only material moves through.
- hold the DNA in place. Their job is transfer.
- In the nucleolus — correct. Yes.
- In the cell wall. The wall does not make them.
- In the cytoplasm only. They are made in the nucleolus first.
- one large and one small subunit — correct. Yes.
- two large subunits. One large and one small.
- one nucleolus. The nucleolus makes the subunits.
- double-layered — correct. Yes.
- single-layered. It has two layers.
- absent in eukaryotic cells. Eukaryotic cells have a well-defined nucleus.