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BIOCHEM (1st yr Med) - Harper's > Protein Synthesis and Genetic Code > Flashcards

Protein Synthesis and Genetic Code Flashcards

1
Q

Makes up the genetic code

A

codon

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2
Q

Translation of the genetic code would be carried out through meditation of adapter molecules such as

A

tRNA

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3
Q

(Features of the Genetic Code)

multiple codons decode the same amino acid - due to wobble

A

Degenerate/Degeneracy

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4
Q

AA that do not have a degenerate feature

A
  • methionine
  • tryptophan
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5
Q

(Features of the Genetic Code)

specific codon will only code for a single AA

A

Unambiguous

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6
Q

(Features of the Genetic Code)

the genetic code during translation does not involve any overlap of codons

A

Non-overlapping

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7
Q

(Features of the Genetic Code)

Once the reading is commenced at a specific codon, there is no punctuation between codons

Message is read in a continuing sequence of nucleotide triplets until termination codon is reached

A

Not punctuated

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8
Q

(Features of the Genetic Code)

  • tRNA in the mitochondria reads 4 codons different from the cytoplasm
  • 22 tRNA for genetic code of mitochondria
  • 31 tRNA for cytoplasmic translation
A

Universal

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9
Q

3 of the 64 codons DO NOT code for specific amino acids termed as () - utilized as translation termination signals

A

non-sense codons

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10
Q

RNA directed synthesis of polypeptides

A

Translation

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11
Q

a two step reaction catalyzed by the aminoacyl-tRNA synthetases

A

Charging (recognition & attachment)

  • of amino acid and tRNA
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12
Q

Amino acid activation forms (1) using the enzyme (2)

The enzyme attaches the AA to the alpha-phosphate of ATP with the concomitant release of pyrophosphate

A

(1) AMP-amino acid enzyme complex
(2) aminoacyl-tRNA synthetase

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13
Q

What happens after amino acid is activated?

A

attachment of the activate AA to tRNA

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14
Q

What enzyme catalyzes the transfer of the amino acid to either the 2’- or 3’-OH of the ribose portion of the 3’-terminal adenosine residue of the tRNA generating the activated aminoacyl-tRNA

A

aminoacyl-tRNA synthetase

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15
Q

link between the amino acid and tRNA

A

ester linkage

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16
Q

(True/False)

Each tRNA is specifically charged (made) to adapt (carry) any amino acid

A

False

Each tRNA is specifically charged (made) to adapt (carry) a SPECIFIC amino acid

17
Q

REGIONS OF tRNA RELEVANT IN TRANSLATION PROCESS

A

(1) D arm - site for proper recognition of a tRNA by its proper aminoacyl-tRNA synthetase

(2) T^C arm - binds the aminoacyl-tRNA to the ribosome

(3) Acceptor arm - at 3’-OH adenosyl terminal, the AA is attached

(4) anticodon region - anticodon for mRNA

18
Q

when the base pairing between the last nucleotide and its corresponding nucleotide of the anticodon is NOT strictly by the Watson-Circk rule (at the 3rd nucleotide of the codon)

A

wobble

19
Q

(True/False)

There is no proofreading during translation only decoding

A

True

20
Q

Active translation of mRNA to protein occurs on

A

polyribosomes/polysomes

21
Q

Protein synthesis begins at (1) where chain elongation occurs by sequential addition of amino acids to the (2) of the ribosome bound polypeptide

A

(1) N-terminus
(2) C-terminus

22
Q

Initiator tRNA

A

met-tRNA for methionine AA as the start

23
Q

Regulation of initiation step of protein synthesis is by

A

elF-2alpha

24
Q

Elongation involves several specific non-ribososmal proteins

A

elongation factors (EFs)

25
Q

(True/False)

During protein synthesis (translation) the ribosome moves down the mRNA to the next codon

A

True

26
Q

Sites in the Ribosome

A

(1) A site - aminoacyl or acceptor site
(2) P site - peptidyl or polypeptide site
(3) E site - deacylated tRNA exit site

27
Q

Elongation Sequence:

1 - translocation of the ribosome on the mRNA

2 - Binding of aminoacyl-tRNA to the A site

3 - Expulsion of the deacylated tRNA from the P and E sites

4 - Peptide bond formation

A

2, 4, 1, 3

28
Q

(True/False)

phosphorylation of the eEF-2 enzyme in the elongation process, by the eEF2 kinase (eEF2K) will inhibit its function

A

True

29
Q

Protein factors for termination of protein synthesis

A

releasing factors

30
Q

The termination codons are

A

UAG, UAA, UGA

31
Q

proteins that hydrolyze the peptidyl-tRNA bond when a stop codon occupies the A site

A

releasing factors (RF)

32
Q

Releasing Factors:

(1) recognizes that a stop codon resides in the A site

(2) recognized the termination codons UAA and UGA

(3) promotes hydrolysis of the bond between the peptide and the tRNA occupying the psite

A

(1) RF1
(2) RF2
(3) RF3 with GTP and the peptidyl transferase

33
Q

Initiation factor that is a prime target for regulation

A

eIF-4E

BIOCHEM (1st yr Med) - Harper's (13 decks)

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