B2.2.2 - Separation of the Nucleus from Cytoplasm

comparison of form. + func. of nucleus and cytoplasm

• nucleus: cell’s genetic material houses in a double-membraned nuclear envelop

• cytoplasm: gel-like substance where most cellular activities (metabolic reactions) occur

what does the compartmentalization of the nucleus lead to?

the physical separation of transcription and translation, allowing for post-transcriptional modification

transcription

synthesis of mRNA by copying DNA in the nucleus

translation

synthesis of proteins from mRNA by ribosomes, which combines amino acids to make polypeptide chains

what structure aids translation?

 tRNA(transfer RNA) carries specific amino acids to ribosomes for polypeptide (protein) synthesis

post-transcriptional modification

Modifications to mRNA after it’s initial transcription and before leaving the nucleus in eukaryotic cells

what are the 3 post-transcriptional modifications that happen in eukaryotic cells?

• capping

• polyadenylation

• splicing

capping

addition of 5' (5-prime) cap to the beginning of mRNA -> helps stability + ribosome binding

polyadenylation

addition of poly-A tail to end of mRNA -> protects from degradation

splicing

removal of introns (non-coding regions), while exons (coding regions) are joined together-> ensures only correct sequence is translated

what is the purpose of post-transcriptional modifications?

Ensures mRNA is stable, correctly formatted, and ready for translation

trade-offs of separation

• Energy cost

• Time delay

• Complexity

how is translation and transcription in eukaryotes different to prokaryotes?

in prokaryotes, transcription + translation are simultaneous -> needs accurate transcription