Transfer and Ribosomal RNAs (G) DUMB B Flashcards
What are transfer RNAs and ribosomal RNAs encoded by?
Genes
What are tRNAs and rRNAs trasncribed as?
Single-stranded RNAs
Are tRNAs and rRNAs linear molecules?
No
Instead, a considerable amount of base pairing occurs within the RNA strand
What does base pairing within the RNA strand allow tRNAs and rRNAs to do?
It allows them to fold into specific conformations that are required for their function
What is the typical length of tRNAs?
70-90 nucleotides in length
How many different tRNAs are there?
At least 20
What is each tRNA encoded by?
Its own gene
What does tRNA contain a high propoteion of?
It contains a high proportion of nucleotides that have nonstandard bases found only in tRNAs
How are nonstandard bases made?
By bse modification after transcription is completed
How many regions on tRNA are important for its function in translation?
Two regions
What is the anticodon sequence on tRNA?
It is a region important for translation
It is complementary to a particular codon and can pair with that codon
What is the importance of the 3’ end of a tRNA?
It is the second important region for translation
It can be covalently linked to an amino acid
What are tRNAs with the same anticodon linked to?
They are always linked to the same amino acid specified by the codon that is complementary to the anti codon
What is a tRNA linked to an amino acid called?
An aminoacyl-tRNA
What enzyme creates a covalent link between a tRNA and the appropriate amino acid?
Aminoacyl-tRNA synthetase
How many aminoacyl-tRNA synthetases are there?
There are 20, one for each amino acid
Each aminoacyl-tRNA synthetase has a specific name. If the amino acid leucine is attached to a tRNA, what is the enzyme called?
Leucyl-tRNA synthetase
What is the process of charging?
A process by which an amino acid is attached to a tRNA
What does a charged tRNA contain?
It contains an amino acid
What is a tRNA without an attached amino acid called?
An uncharged or empty tRNA
What is the ratio of tRNAs and codons? What does that mean?
There are far fewer tRNAs than codons
This means that some tRNAs can pair with more than one codon
ughghhghihi wobble stuff
What are rRNAs a major component of?
Ribosomes
What does a ribosome do with mRNA and aminoacyl-tRNAs?
It brings both of them together and catalyzes the formation of peptide bonds between amino acids
What is a ribosome made up of?
Both proteins and rRNAs/
How many polypeptides are in each ribosome?
Over 50 polypeptides called ribosomal proteins and 3-4 different rRNA molecules
What is each ribosome made out of?
Two parts that interact with one another to carry out translation
One large subunit
One small subunit
What unit of measurement is used for ribosome size?
Svedberg (S) units
How big are bacterial ribosomes?
70S
Small subunit = 30S
Large subunit = 50S
How big are eukaryotic ribosomes?
80S
Small subunit = 40S
Large subunit = 60S
Are Svedberg units additive?
No, because it is not a measure of mass
How many sites on ribosomes are capable of attaching to tRNA?
Three
What are the three ribosomal sites capable of attaching to tRNA?
E site (Exit)
P site (peptidyl)
A site (aminoacyl)
Where are the E, P, and A sites located? What does that mean?
They are located near one another on the ribosome
This means that tRNAs attached to these sites are close to one another
Which ribosomal subunit has the ability to attach to mRNA?
The small subunit
How is the mRNA positioned for the small subunit?
It is positioned so that the codons are located near the E, P, and A sites for tRNA
