1.2 Flashcards
transcription
the synthesis of RNA using the info form DNA
- info is “rewritten”
- resulting RNA is transcript of the gene’s protein building instructions
RNA processing
RNA molecules are spliced and have ‘5 cap and a poly-A tail put on their ends
introns
any nucleotide sequence within a gene that is removed by RNA processing during production of the final RNA product.
exons
a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.
mRNA transport
mRNA formed in nucleus is transported out of nucleus to cytoplasm where it attaches to rRNA (ribosomes)
translation
synthesis of a polypeptide using info in the mRNA
polypeptide
a linear organic polymer consisting of a large number of amino-acid residues bonded together in a chain, forming part of (or the whole of) a protein molecule
protein processing
protein folding and formation of disulfide bridges
RNA polymerase
RNA polymerase is an enzyme that is responsible for copying a DNA sequence into an RNA sequence, during the process of transcription - goes toward 5’ end
what directs the folding of a polypeptide into a specific and unique shape?
its specific amino acid sequence (hydrophobic/hydrophilic/etc)
examples of post-translational modifications that might be required to produce a mature protein
attachments of sugars, lipids, phosphate groups, etc
removal of amino acids
can be cleaved
chains can be synthesized
free ribosomes
located in the cytosol
- synthesizes proteins that function in the cytosol
bound ribosomes
attached to ER or nuclear envelope
- makes proteins of endomembrane system as well as proteins secreted from the cell
endomembrane system
the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles and the plasma membrane.
steps for a protein to be recognized as needing to be synthesized and inserted into the RER?
- polypeptide synthesis begins on a free rRNA in the cytosol
- an SRP binds to the signal peptide, halting synthesis momentarily
- SRP binds to a receptor protein in the ER membrane, part of a protein complex that forms a pore
- the SRP leaves, and polypeptide synthesis resumes with simultaneous translocation across the membrane
- the signal peptide is cleaved by an enzyme receptor protein complex
- the rest of the completed polypeptide leaves the ribosome and folds into tis final conformation
SRP
signal recognition particle
signal peptides can target polypeptides to what other parts of the cell?
mitochondria, chloroplasts, interior of the nucleus, and other organells NOT part of the endomembrane syst.
signal peptides are like….
postal zip codes
