Translation Flashcards Preview

Biochemistry > Translation > Flashcards

Flashcards in Translation Deck (55):
1

Amino acids are activated for synthesis by attachment to tRNA via

Aminoacyl-tRNA synthetase

2

Genetic code feature

Non overlapping code
Triplets of nucleotides -codons
Directional
Contiguous
Degenerate
Single start codon
3 stop codon
First codon sets reading frame
No punctuation

3

During translation how are codons read

In a successive and non overlapping fashion in the 5 to 3 direction

4

First codon

Establishes reading frame

5

What is the single initiation code

AUG encoding for methionine

6

What are the 3 termination codes

UAA, UAG, UGA

7

The code is degerate

Most amino acids coded by more than one codon

Only methionine and tryptophan have one codon

8

What is the adaptive molecule

tRNA
link between mRNA and amino acid sequence of protein

9

Genetic code is universal with few exceptions

Mitochondria use different

UGA encodes tryptophan in vertebrate mtDNA (instead of stop)

AGA/AGG encodes STOP in vertebrate mtDNA (instead of arginine)

10

Mitochondrial tRNA

Uses 22 instead of 32 transfer RNA

11

Pairing of codon and anticodon

Anticodon of tRNA complimentary and anti parallel to the codon

Via h bonds

12

Wobble base

Third nucleotide in the codon is less important for the recognition by tRNA molecule

1st nucleotide of the codon in tRNA

13

What is the wobble hypothesis

Explains why multiple codons can code for a single amino acid. One tRNA molecule can recognize and bind to more than one codon, due to less precise base pair that can arise between the 3rd base of the codon and the 1st position of the anticodon.

1st anticodon runs 3to5
3rd codon run 5 to 3

14

Inosine(I) in the third position of anticodon can h bond with?

U C A

15

Enzyme that connects amino acid to its corresponding tRNA

Aminoacly-tRNA synthetase

16

Wobble pairs that could work

G-U
I-U
I-A
I-C

17

Which position can tolerate mutations

Mutations in the 3rd base of a codon sometimes does NOT least to substitution of amino acids in proteins

Silent mutations

18

Which position leads to mutations?

Mutations in the 1st vase of a codon usually produces a conservative substitution

19

What are the 5 steps of protein synthesis

1. Activation of amino acids
2.Initiation of translation
3. Elongation of translation
4. Termination and ribosome recycling
5. Folding and post translational processing

20

What is the 2D shape of tRNA

Cloverleaf

21

What is the 3D shape of tRNA

Twisted L-shape

22

What must tRNA have at 5 end

G

23

What must tRNA have at 3 end

CCA

24

What is the acceptor arm of tRNA

Where is amino acid is attached to

Carried amino acid Estero ford via carbonyl group to the 3OH of the terminal residue

25

What is the anticodon arm in tRNA

Where the anticodon are
Recognizes codon in mRNA

26

What are the 1st and 2nd reactions of protein synthesis catalyze by

Aminoacyl-tRNA synthetases

27

What is the 3rd reaction catalyzed by in protein synthesis

Ribosome

28

What are the enzymes that estrify or charge amino acids to the tRNA

Aminoacyl-tRNA Synthetases

29

How many aminoacyl-tRNA synthetases are there?

At least 20 different

30

Second genetic code

Aminoacyl-tRNA synthetase need to match each amino acid with current tRNA is viewed as the second genetic code.

Code is molecular recognition of a specific tRNA molecule by a specific synthetase

31

What are the main points on tRNA that are used for recognition by aminoacyl-tRNA Synthetases

Anticodon arm and acceptor arm

32

For which type of amino acids proofreading by the aminoacyl-tRNA synthetase is necessary to maintain the high level of fidelity of translation?

Amino acids with different properties by same shape like valine and isoleucine

33

What are the three main principles of ribosome structure

1. Two unequal subunits- small and large

2. Compact cores of each subunit are formed by self folding specific rRNA molecules

3. Multiple ribosomal proteins decorate compact rRNA cores

34

Bacterial ribosome size

70S ribosome
30S and 50S sub particle

35

Eukaryotic ribosomes

80S and 40S and 60s subunit

36

What is the composition of bacterial ribosome

65% rRNA and 35% protein

37

Number of proteins in small (30s) bacterial ribosome

21

38

Number of proteins in small (40s) eukaryotic ribosome

40S

39

Number of proteins in large (50s) bacterial ribosome

36

40

Number of proteins in large (60s) Eukaryotic ribosome

47

41

Bacterial ribosome

70S
Large (50s)- 2 rRNA (23S and 5S), 36 proteins
Small(30s)- 1 rRNA (16S), 21 proteins

42

Eukaryotic ribosome

80S

Large (60s)- 3 rRNA (28s, 5s, 5.8s), 47 proteins

Small(40s)- 1 rRNA (18s), 33 proteins

43

Ribosome tri function

Decoding- small subunit
Enzymatic- large subunit
Molecular/ translocation function

44

Where does decoding occur

A site of 30s subunit

45

Catalysis occurs in the

PTC of the 50s subunit

46

Shine dalgarno sequence

Initiating AUG codon of mRNA is guided to its correct position by this.
On mRNA
Upstream of start codon

47

What is the difference in imitation of eukaryotes and prokaryotes

How the ribosome determines where to start from.
In bacteria- start codon is not always AUG
Eukaryotes- start synthesis at first AUG... only one coding region

48

Ternary complex in elongation cycle of ribosome

Aminoacyl+EF-Tu +GTP

49

Decoding step 1

Tertiary complex binds to the A site of 70S ribosome

50

Peptidyl transferase reaction 2

N-formyl-methionyl group is transferred from its tRNA in P site to the amino acid in the A site

51

Translocation step 3

EFG-GTP catalyzes transition of ribosome by one codon towards the 3 end of the mRNA clearing A site for the next

52

What are the two main elongation factors

EF-Tu-GDP and EFT-GTP

53

Peptidyl transferase reaction

Nucleophilic attack

Peptidyl tRNA in P site and Amioacyl tRNA in A site

54

Termination of protein synthesis

Recycling factors
Hydrolyze ester bond between the peptide and tRNA

55

Signal recognition signal

Protein complex in cytoplasm, temporarily pauses translation