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Protein Synthesis 1
Slideshow
| Question | Answer |
|---|---|
| The ribosome reads mRNA from ___ to ___ | left, right |
| How many possible reading frames? | 3 |
| How many sense codons for all amino acids? | 61 |
| How many initiator codons? | 1 |
| Initiator Codon name | methionine |
| How many termination codons? | 3 |
| Which position of codon is least important? | Third |
| How was code deduced for codons? | Synthrtic mRNAs, tRNAs and ribosomes used with various radioactive and non-radioactive amino acids |
| The coordinator 1 | 40S Ribosome |
| The message | mRNA |
| the Adaptors | tRNA |
| the links | amino acids |
| the chargers | aatRNA synthases |
| the coordinator 2 | S ribosome |
| mRNA structure, in order | 5' cap, 5'UTR, initiation codon, coding region, termination codon, 3'UTR, Poly A tail |
| Name of 5' Cap Compound | 7-methylguanosine |
| How is 7-methylguanosine connected to mRNA? | 5' to 5' triphosphate bridge |
| How is tRNA charged? | by its amino acid |
| Where does the tRNA bind? | to its respective codon |
| What are the names of the 3 loops on a tRNA? | D loop, T loop, anticodon loop |
| What is the main function of aminoacyl tRNA synthetases? | Links tRNA with specific amino acid through a high energy bond and consumption of ATP |
| Explain chemically how tRNA is aminoacetylated? | ATP turns into AMP as an AMP group replaces the OH in the carboxyl acid on an amino acid. The AMP group is then replaced when it detaches to form an O- bond with the tRNA. |
| What are the ribosomal subunits in eucaryotes? | 40S and 60S |
| What are the ribosomal subunits in prokaryotes? | 30S and 50S |
| Name 2 funcitons of ribosomes | 1. Coordinate translation 2. Catalyze peptide bond formation |
| In what order is DNA synthesized in rRNA? (P, A, E) | EPA |
| What does A , P, And E stand for individually? | A - aatRNA (Attaching amino acid to tRNA) P - peptidyl tRNA E - exit site for tRNA |
| Recall the four basic steps in elongation | 1. Trna enters the A site 2. The Bond is made between amino acids and broken from trna in P site 3. Larger subunit shifts right, moving both tRNA over one 4. Smaller subunit shifts right to match up with the next codon site |
| What is it called when the amino acid is bonded with the continuing chain in elongation/ | Peptadil transfer reaction |
| What are elongation factors? | G proteins that have bound GTP or GDP and aid in the steps of elongation |
| What does EF1alpha do? | They carry tRNA's to the ribosome |
| What does EF2 do? | It carries GTP to the A site and allows for energy release to move the bottom subunit along the mRNA |
| What does eIF2 do? | Binds to the methionine-carrying tRNA to initiate the pre-initiation complex |
| What does eIF4E do? | Binds to the 5' cap of mRNA |
| What does eIF4G do? | Recognizes polyA binding protein and is bound to polyA tail |
| When the pre-initiation complex is created, what happens next? | The complex searches the mRNA for the first start codon |
| When the start codon is found in pre-initiation, what happens next? | The eIF2 dissociates and the large ribosomal subunit attaches to the bottom subunit |
| Are there tRNA's that recognize stop codons? | Nope |
| What do ERF3 and ERF1 do? | These are release factors that bind to the A-site when a termination codon is detected |
| What happens when ERF3 and ERF1 are bound? | They release energy in form of GTP and hydrolyze water to attach to the end of the amino acid chain |
| What is a nonsense codon? | A stop codon |
| What does EIF6 do? | Binds to the 60S subunit when translation has ended |
| What does eIF3 do after the protein is released in translation? | It remains attached to the smaller subunit. aka the 40S subunit |
| What are polyribosomes? | mRNA that is circular can have multiple ribosomes attached to it creating more than one sequence of proteins at a time |
| How many high energy bonds are needed for each amino acid to a chain? | FOUR |
| What are the energy requirements to make these bonds? | 2 need to charge tRNA with Amino acid w/ ATP 1 is needed to occupy A site on ribosome with GTP and EFIalpha 1 is needed to create a peptide bond with EF2-GTP |
| What are two things to note about the third base in a codon? | It is either irrelevant, or only purines/pyrimidines are distinguished from one another |
| What is wobbling? | One tRNA can recognize more than one codon, so often it does not worry about binding to the third codon, as long as the first two are correct. i.e. G-U pairing can occur |
| What is I? | I is Inosine, which is a modified guanosine |
| What can I bind to? | It can bind to A,C, or U |
| In eucaryotes, what can U bind to? | A, G, or I |
| In eucaryotes, what can C bind to? | G or I |
| In prokaryotes, what can U bind to? | A, G or I |
| In prokaryotes, what can C bind to? | G or I |
| In prokaryotes, what can A bind to? | U or I |
| In prokaryotes, what can G bind to? | C or U |
| What does polycistronic mean and to what does it apply | This means one mRNA can make several different proteins. Occurs in procaryotic mRNA |
| What does monocistronic mean and to what does it apply | This means one mRNA only codes for a single protein. Occurs in eucaryotic mRNA |
| What is unique about prokaryotic mRNAs? | The ribosomes can bind internally, and not only on the ends of the mRNA |
Created by:
neeck
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