tRNA and aminoacyl tRNA synthetases

Question 1

how many nucleotides long is tRNA?

Answer 1

75-90 nucleotides long

Question 2

the ___ end of tRNA is linked to an ____ ____, which is specifically attached to the _____ base

Answer 2

3’
amino acid
adenine

Question 3

name a unique feature about the structure of tRNA

Answer 3

it contains many modified bases, specifically in the arms of tRNA

Question 4

true or false: all tRNAs have a similar structure because they need to bind to a particular part in ribosomes

Answer 4

true

Question 5

the ___ position of the codon is the ___ position of the anticodon, and at that position there will be flexibility - this is called “_____”

Answer 5

3rd
1st
wobble

Question 6

what does “I” stand for in tRNA?

Answer 6

inosine

Question 7

what is unique about inosine?

Answer 7

it has expanded base pairing capabilities (can bind to A, U, C)

Question 8

inosine is ______ adenosine

Answer 8

deaminated

Question 9

the _______ is not involved in checking to see if the correct amino acid is attached to tRNA

Answer 9

ribosome

Question 10

____ ________ are involved in attaching the appropriate ____ ___ onto the corresponding tRNA

Answer 10

tRNA synthetases

amino acid

Question 11

what’s the short term for aminoacyl tRNA synthetase?

Answer 11

aaRS

Question 12

what is a charged tRNA?

Answer 12

tRNA with an amino acid attached to it

Question 13

during the activation of an amino acid, how many ATPs are used?

Answer 13

2

Question 14

the ____ ___ does a nucleophilic attack on the __ phosphate group of ATP, thus releasing ______

Answer 14

amino acid
alpha
pyrophosphate

Question 15

aminoacyl-AMP is referred to as a _____ _______ because it has both a phosphoester bond and an ester bond

Answer 15

mixed anhydride

Question 16

true or false: there is a class I aminoacyl-tRNA synthetase and class II aminoacyl-tRNA synthetase

Answer 16

true

Question 17

for class I aaRS, the __ OH attacks the carbon (on the ester) of the amino acid, and releases ___

Answer 17

2’

AMP

Question 18

for class II aaRS, the ___ OH attacks the carbon (on the ester) of the amino acid and releases __

Answer 18

3’

AMP

Question 19

in both class I and class II aaRS, the amino acid ends up on the ___ position of adenine and attached to _____

Answer 19

3’

tRNA

Question 20

the amino acid on the 2’ position moves to the 3’ position via a __________ reaction

Answer 20

transesterification

Question 21

how are tRNA synthetases similar to DNA polymerase I?

Answer 21

if the incorrect amino acid is added on, then it flops over to the editing site where it will be removed (DNA polymerase 3’ to 5’ exonuclease does the same thing but w/ nucleotides)

Question 22

what are the tradeoffs for accuracy in translation?

Answer 22

energy and time

Question 23

true or false: some aaRS do not proofread at all

Answer 23

true

Question 24

the aaRS that puts the amino acid ______ on does not have any proofreading activity…why not?

Answer 24

tyrosine
because the catalytic site for tyrosine is different in that tyrosine is bulky, and it has hydrogen bonding for the OH group (allowing for specificity against Phe)

Question 25

what are the 2 steps required for formation of aminoacyl-tRNA?

Answer 25

1. activation of the amino acid by attaching it to adenine

2. formation of charged tRNA