14-18

Question 1

how big are ribosomes

Answer 1

2.5-4 mDa

Question 2

what does 26 s mean

Answer 2

26 micrometers per second under influence of a million gravities

Question 3

svedberg units facts

Answer 3

not directly additive, rate of sedimentation not weight

Question 4

purpose of protein arms in rRNA

Answer 4

basic to help pack the negative phosphate backbone

Question 5

where is the L7/12 stalk

Answer 5

large subunti

Question 6

ribosome inactivating protein

Answer 6

TCS- trichosanthin

Question 7

alphaproteobacteria

Answer 7

23- cleaved into 3 molecules- 5.8 like, 14s, 16s

shows that ribosomal RNA is cleaved from larger precursors

Question 8

fragmented rRNA genes

Answer 8

5.8 is the 5’ end of the larger rRNA in bacteria

5.8+28s=23s

Question 9

rRNA chemical modifications

Answer 9

ribose 2’OH methylation
psuedouridlyation

Question 10

how big are tRNA molecules

Answer 10

75-94nt

Question 11

what nucleotides are in the T loop

Answer 11

ribothymidine
pseudouridine

Question 12

endonuclease RNase P

Answer 12

trims the bacterial tRNA at the 5’ end

Question 13

fun fact about CCA enzyme

Answer 13

does not use a template
two binding pockets
targets unstable tRNAs for degradation- ones that have multiple CCA

Question 14

what is found at the 3’ end of the anticodon and what does it do

Answer 14

hypermodified purine and prevents base pariing with codon in mRNA to allign the codon and anticodon properly

Question 15

what does inosine pair with

Answer 15

U, C, A

Question 16

what does C pair with

Answer 16

G

Question 17

what does G pair with

Answer 17

C or U

Question 18

what does A pair with

Answer 18

U

Question 19

what does U pair with

Answer 19

G, or A

Question 20

how many tRNAs are needed to decipher 4 codons

Answer 20

no more than 2

Question 21

how many anticodon specific targets are there and how many tRNAs

Answer 21

two anticodon specific targets but each one has more than one distinct tRNA

Question 22

binding pockets for aaRS

Answer 22

proper AA
proper tRNA
ATP

Question 23

reaction of adding AA to tRNA

Answer 23

two steps- SN2
first is activating AA with AMP for LG (adenylated AA)- releases PPi and provides energy. activated AA remains bound to enzyme
OH on terminal adenosine on tRNA attacks carbonyl C of AA covalently joined to AMP- catalyzed by aaRS

Question 24

class I aaRS

Answer 24

use 2’OH of adenine on tRNA
mostly monomeric enzymes
has about 10 members

Question 25

class II aaRS

Answer 25

attatch AA to 3'OH on tRNA adenine mostly dimeric enzymes has about 10 members

Question 26

does it matter what OH group on adenine attacks AA

Answer 26

no bc AA can isomerize readily bw 2'OH and 3'OH no terminal adenosine peptide synth requires only 3'OH

Question 27

bond bw AA and tRNA

Answer 27

HIGH ENERGY and susceptible to hydrolysis protected by elongation factors EF-Tu- bacteria eEF1A- euk

Question 28

what do aaRS recognize

Answer 28

identity elements on tRNA sequence and structural features identity elements primarily in anticodon loop or acceptor stem

Question 29

class I aaRS identity elements

Answer 29

minor goove of acceptor stem

Question 30

class II aaRS structural features

Answer 30

major groove of acceptor stem

Question 31

tRNAala identity element

Answer 31

G3:U70

Question 32

steps of adding correct amino acid

Answer 32

likely aa is selected and activated and bound by enzyme then aa is proof read to make sure it is correct

Question 33

correct aa for tRNA is

Answer 33

cognate AA

Question 34

correct tRNA for AA

Answer 34

cognate tRNA

Question 35

what does the correct AA addition to its cognate tRNA depend on

Answer 35

aaRS have separte AA and editing sites

Question 36

two sieves of aaRS

Answer 36

1. blocks antyhing too large 2. blocks anything too small

Question 37

what removes AA in the small seive

Answer 37

if they fit in the editing site, they are removed

Question 38

when is the correct AA checked

Answer 38

either after first or second step of Aminoacylation reaction some check aminoacyl adenylate after activation- editing pretransfer some check aminoacylated tRNA- editing post transfer

Question 39

correlatino between editing mechanism and class of aaRS

Answer 39

no correlation