Module 34 Flashcards
Translation
Translation
The process where a molecule of mRNA is used to guide the synthesis of a protein
Built by specialized molecular structures within the cell
What reads the mRNA
ribosomes and tRNA
Ribosomes
Site of protein synthesis
Organize the process of translation
-Catalyze the reaction that joins amino acids together
-Translate proper reading frames
-Holds in place the various components required for translation
What makes up ribosomes
rRNA and protein
Ribosome structure
1 large and 1 small subunit
Subunits are made from 1-3 types of rRNA and 20-50 types of ribosomal proteins
Reading Frames
Different ways/combinations of parsing letters into words
XWTHEBIGBOY
Codons
In mRNA, Codes for a single amino acid in the polypeptide chain
tRNA
Translate each codon into an amino acid
-acts as a bridge from the mRNA to the protein sequence
What does each end of tRNA do
one end binds to the mRNA strand (anticodon segment) and the other attaches to an amino acid (sequence that binds to a specific amino acid)
Anticodon
three bases at the bottom of the tRNA molecule that undergo base pairing with the corresponding codon in the mRNA
Why does the first base of the mRNA codon pair with the last base on the anticodon
first= 5’
last = 3’
They are antiparallel
How are amino acids attached to tRNA
By enzymes called Aminoacyl tRNA synthetases
How many Aminoacyl tRNA synthetases do u have if there are 20 different amino acids being coded
20
Genetic Code
Relationship between the three nucleotides (codon) and its specific amino acid in a protein
61 codons that correspond to 20 amino acids
Why is the genetic code “redundent”
Multiple codons can code for the same amino acid
Initiation Codon
The codon where translation begins
AUG –> (Met/ methionine) amino acid
In what direction are polypeptides synthesized in
Amino end to the carboxyl end
What end does methionine form
the amino end any polypeptide being synthesized
Stop Codons
Signal where translation terminates and the protein is released
-UAA, UAG, UGA
Nicknames for stop codons
Nonsense codons or termination codons
Codon evidence for a common ancestor
Genetic code is nearly universal
Three processes of translation
- Initiation
- Elongation
- Termination
Translation Initiation
The initiator codon, AUG, is recognized and the Met amino acid is established in the new polypeptide chain
Translation Elongation
Successive amino acids are added to the growing chain, one by one
Translation Termination
The addition of amino acids stops and the completed polypeptide chain is released from the ribosome
What does the position of the AUG establish
The translation reading frame
The initiation complex
Protein initiation factors bind to the mRNA, the tRNA w/ the met, and the small ribosome unit
Moves along mRNA until it reaches the UG codon
When does the large ribosomal unit join the initiation complex
When the AUG codon is encountered by the initiation complex
What happens when the large ribosomal unit joins the initiation complex
The initiation factors are released, and the next tRNA is ready to join the ribosome
Dehydration Synthesis
H2O is a product
Builds products
Hydrolysis
H2O is a reactant
Breaks down reactants
What binds amino acids together and how does this bond form
Peptide bonds are formed
Dehydration synthesis forms these bonds
What catalyzes the dehydration synthesis between amino acids
An RNA molecule within the large RNA subunit
When is the OG tRNA released from the ribosome
When the ribosome shifts one codon to the right
What creates new site for the next tRNA to come into place
When the ribosome shifts one codon to the right
What steps are repeated during elongation
New tRNA binds to the ribosome
A peptide bond forms between the amino acids
The tRNA is released from the ribosome through a shift
How does the ribosome bind to tRNA during each step of elongation
The tRNA anticodon base pairs to the mRNA codon
What kind of end of the polypeptide chain does the newest amino acid become
The new carboxyl end of the polypeptide chain
Where and on what end of elongation factors bond to on the mRNA
Bond to GTP molecules that serve as a cap on the 5’ end of the mRNA molecule
What parts of elongation require energy
The movement of the ribosome along the mRNA molecules
The formation of the peptide bond between amino acids
Where does the energy for the steps in elongation come from
Elongation factors (proteins)
They break high-energy bonds
When does initiation begin
When the initiation factors are bond to the small ribosomal subunit, the tRNA carrying the Met, and the mRNA
What happens when the stop codon is reached
Polypeptide synthesis stops
A protein release factor is released and binds to the ribosome
What does the protein release factor do when it attaches to the ribosome
It causes the bond connecting the polypeptide to the tRNA to break
Creates the carboxyl terminus of the polypeptide + completes the chain
What creates the carboxyl terminus of the polypeptide during termination
When the protein release factor binds to the ribosome
When does the release factor bind to the ribosome
When the termination codon is encountered
Where is the initiation complex formed in eukaryotes
At the GTP cap, which is released once it reaches the AUG codon
Do prokaryotes have GTP caps
No
Where are the initiation complex found in prokaryotes
They are formed at one or more than one INTERNAL SEQUENCE that is then followed by AUG
How many polypeptides can be made by a mRNA strand in a eukaryote
Only one
How many prokaryotes can be synthesized by on mRNA strand in a prokaryote
Multiple
Why can prokaryotes form multiple polypeptides from one mRNA strand
They have no GTP caps
Their ability to initiate translation internally
It is an OPERON
Operon
Gene organization in which a group of genes are located in a row along DNA and are transcribed as a single unit from one promoter
Pros of operons
Allows all the protein products to be expressed together whenever they are needed
-such as for the successive steps of the synthesis of smaller molecules, such as amino acids
