Translation Flashcards

1
Q

What are the basic requirements for translation

A

mRNA, charged tRNA, ribosomes, additional factor proteins, GTP

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2
Q

What are the three types of tRNA

A

mRNA, tRNA, rRNA

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3
Q

What does mRNA do

A

it has codon sequences that code for specific amino acids

carries gene information from DNA to ribosome

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4
Q

what does rRNA do

A

it is the major component with ribosomes

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5
Q

What does the small subunit and large subunit of a ribosome do

A

small subunit: attaches to mRNA

large subunit: binds the tRNA and catalyzes peptide bond formation

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6
Q

what does tRNA do

A

it carries the amino acid to the ribosome and pairs its anticodons with the codons on the mRNA

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7
Q

what are the two basic steps of translation?

A

tRNA charging, where the tRNA and its amino acid are correctly matched and catalyzed by an enzyme

A correct match between the tRNA codon and mRNA codon in the ribosome

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8
Q

what is the enzyme required to catalyze tRNA and its correct amino acid

A

aminoacyl-tRNA synthetase

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9
Q

What do aminoacyl-tRNA synthetase do

A

they use ATP to covalently bond a specific amino acid to a tRNA

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10
Q

What are the two primary functions of a ribosome

A

bring together mRNA and tRNA

form peptide bonds

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11
Q

what forms the peptide bonds in a ribosome

A

peptidyl transferase (enzyme)

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12
Q

What are the 3 sites on ribosomes?

A

A, P, E

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13
Q

What does the A( aminoacyl) site do

A

it holds tRNA with the next amino acid to be added

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14
Q

what does the P (Peptidyl) site do

A

it holds the tRNA with the growing polypeptide

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15
Q

what does the E-site do?

A

It is the exit site where tRNAs leave

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16
Q

what side of the poly peptide chain are the amino acids added?

A

the C terminus

17
Q

What is the first part of the initiation complex assembly

A
  1. a mRNA, a small ribosomal, initiation facots, and the “initiator tRNA charged with Methionine assemble first at the P site
18
Q

What is the second part of the initiation complex assembly

A

The complex scans the mRNA for the start codon (AUG)

19
Q

What is the third part of the initiation complex assembly

A

A large ribosomal subunit binds to complete the complex and translation begins

20
Q

how does termination occur in translation

A
  1. a stop codon in mRNA reaches the A site
  2. the A site accepts a protein “release factor”
  3. the “release factor” causes the addition of a water molecule instead of an amino acid
  4. this reaction releases the polypeptide and the translation assembly comes apart
21
Q

How does a cell expend energy to from an initiation complex?

A

it expends energy obtained by hydrolysis of a GTP molecule to form the complex

22
Q

Which direction is the polypeptide synthesized

A

it starts at the initial methionine at the N-terminus and towards the final C- Terminus Carboxyl end

23
Q

How is energy used in elongation?

A

The codon recognition of the anticodon and codons requires hydrolysis of one GTP

24
Q

What does GTP do in codon recognition?

A

it increases the accuracy and efficiency

25
How is GTP used in the last step of elongation
it is hydrolyzed to provide energy for the translocation step, where the tRNA in the p-site is released through the E site
26
When does termination begin
when the stop codon in the mRNA reaches the A site
27
What happens when the stop codon is reached at the A site
a release factor protein binds to the stop codon and this causes the addition of a water molecule instead of an amino acid to the polypeptide chain
28
The breakdown of the translation assembly requires what?
2 more GTP molecules
29
What are polyribosomes
they are formed when multiple ribosomes translate a single mRNA simultaneously
30
What do polyribosomes allow?
They allow a cell to make many copies of a polypeptide quickly
31
In what types of cells do polyribosomes occur in?
Prokaryotes and Eukaryotic Cells
32
What is coupled transcription and translation and where does it occur?
it is when transcription and translation occurs simultaneously it occurs only within prokaryotes
33
How do proteins made by ribosomes on the rough ER get into the ER lumen
1. the polypeptide synthesis begins in the ribosome 2. an SRP binds to a signal peptide attached to the N-terminus of the polypeptide 3. the SRP brings the ribosome to a receptor protein 4. the SRP detaches and polypeptide synthesis resumes 5. A signal Cleaving enzyme cuts off the signal peptide 6. the completed polypeptide folds into its final conformation
34
what happens at each addition
1. codon recognition 2. peptide bond formation 3. translocation