Chapter 14 Flashcards
Define translation
Use of mRNA as instructions to make a protein
What 4 things does translation (eukaryotic) use?
mRNA, ribosomes, amino acids, and tRNAs.
Define ribosome
Machine that reads mRNA and combines amino acids
Define amino acids
Monomers of proteins
What does mature eukaryotic mRNA contain (7 things)
5’ cap
5’ untranslated region (5’ UTR)
Start codon
Open reading frame
Stop codon
3’ untranslated region (3’ UTR)
Poly-A tail
What does mature prokaryotic mRNA contain (6 things)
5’ UTR
Shine-Delgarno Sequence
Start codon
Open reading frame
Stop codon
Poly-A tail
What does 5’ cap do?
Protection and translation initiation in eukaryotes
What does 5’ untranslated region do?
Helps control initation of translation in both eukaryotes and prokaryotes
What does a 3’ UTR do?
Helps control the amount of translation in eukaryotes
What does the poly-A tail do?
Proides stability and protection
What are the differences in prokaryotes and eukaryotes mRNA?
Prokaryotes do NOT have a 5’ cap
Prokaryotes contain a Shine-Delgarno sequence and additional ORFs
Define small subunit
Helps initiation of translation by finding and binding to the start codon
Made up of multiple proteins and RNA molecules.
Define the large subunit
accepts tRNAs and makes polypeptides.
Made up of multiple proteins and RNA molecules.
Define a dalton
The mass of 1 Hydrogen. Used to measure protein size.
What are the 3 main components of the large subunit and what do they do?
- Acceptor (A) Site - new tRNAs bind here
- Peptide (P) Site - Polypeptide elongates here
- Exit (E) Site - Old tRNA leaves from here
What does rRNA do?
In the large subunit, the rRNA catalyzes polypeptide formation.
Define ribozymes
rRNA molecule that catalyzes a reaction
How many amino acids are there? What are the unconventional amino acids?
20 conventional.
2 unconventional: selenocysteine in humans, and pyrrolysine in bacteria.
What do all amino acids contain?
An amino group, carboxyl group, central carbon, and a chemically distinct side chain (R-group).
How does the ribosome link multiple amino acids together?
Peptide bond, with Carboxyl group being attached to the amino group of the next.
Define N terminus
Front end of polypeptide - the exposed amino group
Define C terminus
Back end of polypeptide - exposed carboxyl group
Like a DNA strand going 5’ -> 3’, the polypeptide goes ….
N terminus -> C terminus
Define tRNA
Transfer RNA reads the codon and brings the corresponding amino acid.
Define anticodon
Region complementary to the codon
Define acceptor stem
Region that brings the amino acid
How many different tRNAs are there?
64 - each codon needs a different tRNA
Define tRNA charging
Chemical reaction that first attaches amino acids to tRNA. The tRNA then take the amino acid to the ribosome
Define aminoacyl tRNA synthetases
Enzymes that catalyze the attachment of the amino acid to the tRNA.
Each amino acid has a different synthetase.
What are the steps to prokaryotic translation initation?
- Small ribosomal subunit binds to the Shine-delgarno sequence
- Initation factors (IFs) bring methionine tRNA to the start codon
- Large ribosomal subunit joins and IF’s leave
Where is the shine-delgarno sequence?
~6 nucleotides ahead of the AUG start codon
What are the steps of elongation in prokaryotes?
- A new, charged tRNA enters ribosome A site. The elongation factor EF-Tu carries the tRNA in.
- Ribosome shifts forward and makes a peptide bond between the amino acids in the A and P sites.
- Old, now uncharged, tRNA leaves the E site as a new one enters the A site
What is EF-Tu
Elongation factor in prokaryotes that carries tRNA into the A site
What are the steps for translation termination in prokaryotes?
- Ribosome reaches stop codon
- Release factor enters the A site. Causes dismantling of the complex.
What are the 3 main differences between eukaryotic and prokaryotic translation?
- Eukayotes have a 5’ cap instead of a shine-delgarno sequence to help small subunit bind to the mRNA.
- Eukaryotes have more initiation factors - more regulation
- mRNA may form a circle in Eukaryotes allowing for translation to quickly repeat.
Define polysomes
When multiple ribosomes attach to the mRNA, allowing for multiple translations to occur. This allows for many proteins to be produced quickly.
What 3 steps do new proteins undergo?
- Folding
- Protein targeting
- Post-translational modifications
Define protein folding
Adoption of a 3D structure based on its amino acid sequence
Define protein targeting
Being taken to its proper location in the cell, based on instructions embedded in its sequence.
Define post-translational modifications
Individual amino acids get chemically altered, changing the function of the protein.
