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translation Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the start codon. what A.A. does it code for

A
  • AUG= Met
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2
Q

broadly, what does translation do (2)

A

synthesis of polypeptide directed by mRNA

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3
Q

1 codon= how many nucleotides = how many A.A.

A

3 nucleotides =1 A.A.

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4
Q

each codon specifies what

A

an A.A.

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5
Q

What is redundancy in translation

A

most amino acids are specified by more than one mRNA codon

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6
Q

What is no ambiguity in translation

A

each codon specifies one A.A.

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7
Q

in ribosome, what does P site do

A

tRNA holding growing PP bound here

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8
Q

in ribosome, what does A site do

A

tRNA holding next A.A.

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9
Q

in ribosome, what does E site do

A

empty tRNA goes there

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10
Q

what is in the large subunit of ribosome

A
  • P site
  • A site
  • E site
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11
Q

what is in the small subunit of ribosome

A

mRNA binding site

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12
Q

wobble theory

A

when tRNA goes to bind to codon, only 1st 2 need to match. If 3rd doesn’t, will wobble

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13
Q

what does rRNA do

A

associates w protein to form ribosome

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14
Q

what does mRNA do (3)

A
  • generated from DNA
  • serves as template for prot. synthesis
  • contains info in form of codons
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15
Q

what does tRNA do ?

A
  • attaches to specific A.A. at 3’ end
  • brings A.A. to ribosome via its anticodon
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16
Q

what is an anticodon

A

sequence of 3 bases that are complimentary to the bases on mRNA

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17
Q

of tRNA identical

A

no

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18
Q

what enzyme catalyzes attachment of A.A. to tRNA

A

aminoacyl-tRNA synthetase (each A.A. has specific one)

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19
Q

is the catalysis of attachment of A.A. to tRNA endo or exo

A

endergonic

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20
Q

how does aminoacyl-tRNA synthetase get its energy

A

AMP from ATP

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21
Q

what are the 3 steps of translation

A

initiation, elongation, termination

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22
Q

what do all steps of translation require

A

protein factors and energy (GTP hydrolysis)

23
Q

what does initiation require

A

initiation factors

24
Q

what are the 3 components of initiation

A
  1. binding of small ribosomal subunit to mRNA
  2. binding of initiator tRNA to mRNA
  3. attachment of large ribosomal subunit to small subunit
25
Q

what does iniatiator tRNA contain

A

anti-codon (3’-UAC-5’) + A.A. Met

26
Q

what does initiator tRNA base pair with on mRNA

A

AUG start codon

27
Q

what does the attachment of the 2 ribosomal subunits require

A
  • GTP
  • initiator tRNA in P-site
28
Q

what does elongation require

A

elongation factors

29
Q

what are the 3 components of elongation

A
  • codon recognition
  • peptide bond formation
  • translocation
30
Q

what is codon recognition

A

in A site, mRNA codon forms H-bond with anticodon of incoming tRNA, requires GTP

31
Q

what is peptide bond formation

A
  • growing polypeptide transferred from tRNA in P site to tRNA in A site
  • peptide bond formed b/n NH2 terminus of new A.A. and the COOH end of growing PP
32
Q

what is translocation

A
  • tRNA w/ growing polypeptide in A-site is moved to P-site
  • empty tRNA in P-site moved to E-site & exits ribosome
  • codon in A site now ready to receive next aminoacyl tRNA
  • requires GTP
33
Q

what happens during termination

A
  • stop codon reaches A-site
    release factor binds to the codon (NOT tRNA)
  • hydrolysis of bond b/n tRNA in P-site and polypeptide chain occurs
  • polypeptide released
  • ribosome dissociates and leaves mRNA
  • breakdown of the translation assembly complex requires E (2GTP))
34
Q

are polyribosomes found in prokaryotes or eukaryotes

A

both

35
Q

what are polyribosomes

A

several ribosomes that can translate the same mRNA at once

36
Q

when can a second ribosome assemble

A

when the first ribosome passes the AUG codon

37
Q

what is the result of polyribosomes

A

mRNA makes many copies of same polypeptide

38
Q

what are the two types of ribosomes found in cell

A
  1. free (cytosolic proteins)
  2. bound to rough endoplasmic reticulum (membrane and secreted proteins)
39
Q

synthesis of ALL proteins starts where

A

free ribosomes

40
Q

what directs the ribosome to become attached to ER

A

signal peptides (tell ribosome it needs to attach to RER)

41
Q

where are signal peptides found

A

N-terminus of growing polypeptide

42
Q

what does signal peptide consist of

A

20 hydrophobic A.A.s

43
Q

what is the signal recognition particle (SRP) (3)

A

composed of protein and rna
recognizes signal peptide
brings ribosome (w/ polypeptide) to a receptor on ER

44
Q

what is the SRP receptor (2)

A
  • protein complex
  • built into mb of ER
45
Q

how do signal peptides target protein to ER (5 steps)

A
  1. all prt synthesis starts on free rib
  2. srp recognizes signal peptide, protein synthesis pauses
  3. srp binds to srp receptor, bringing growing PP to ER
  4. srp detaches and port synthesis continues
  5. signal peptide is cleaved off by an enzyme
46
Q

what happens after proteins brought to ER (3)

A
  • secreted proteins remain in ER lumen
  • membrane proteins embedded in ER membrane
  • ribosomes without signal peptide stay free in cytosol.
47
Q

say if these characteristics are for eukaryotic or prokaryotic protein synthesis
1. have nucleus
2. lack nucleus
3. transcription and translation are seperated
4. transcription and translation are coupled
5. mRNA processing occurs
6. RNA polymerase requires transcription factors

A
  1. E
  2. P
  3. E
  4. P
  5. E
  6. E
48
Q

what is a mutation

A

any change in genetic material of cell (at DNA level not at polypeptide sequence level)

49
Q

what is a point mutation

A

changes in one base pair in a single gene

50
Q

what are the 2 types of point mutations

A
  1. base pair substitution (replace one nucleotide with another)
  2. base pair insertion or deletion (addition/ loss of nucleotides)
51
Q

what are the 4 types of base pair substitutions

A
  1. silent mutation (no change in AA sequence)
  2. missense (AA changes, new AA different properties)
  3. neutral (AA changes, similar proprties)
  4. nonsense (new codon codes for stop codon, translation prematurely terminated, truncated prot)
52
Q

what is the type of base pair insertion or deletion

A

frame shift mutation: alter reading frame of mRNA, insertion/deletion is not a multiple of 3, all nucleotides downstream mutation are not properly grouped

53
Q

what are the two causes of mutations

A
  1. spontaneous mutations: errors occur during DNA replication, repair, recombination
  2. mutagens: physics/chem agents interacting w dna

Biology (6 decks)

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