3.4 translation

Question 1

rRNA aminoacyl synthetases

Answer 1

• enzymes that bind AA to correct tRNA molecules
• are “translators” of the code
• one enzyme for each AA

undergo base pairing with the corresponding codon
○ Directly responsible for actually translating the codon sequence in a nucleic acid to a specific amino acid in a polypeptide chain

Question 2

charged tRNA

Answer 2

tRNA with amino acid

Question 3

process to charge tRNA

Answer 3

1. aminoacyl tRNA synthetase (enzyme) binding to a specific amino acid
2. it then transfers the amino acid to the appropriate tRNA molecule

each AA has a specific aminoacyl tRNA synthetase

Question 4

ribosomal subunits

Answer 4

large and small
○ Each composed of 1-3 types of ribsomal RNA and 20-50 types of ribosomal protein

Question 5

what does rRNA do

Answer 5

is in ribosome!

is what catalyses the peptide bond

Question 6

translation in EUKARYOTES

Answer 6

initiation in eukaryotes is at the 5’ cap, and the first AUG is the start codon
monocistronic mRNA (code for just one polypeptide)

Question 7

translation in BACTERIA

Answer 7

polycistronic mRNA

Initiates at any Shine-Dalgarno sequence

can code for several polypeptide

multiple start and stop codons!!

Question 8

polycistronic mRNA

Answer 8

multiple protein-coding genes on the same RNA

Question 9

how does the ribosome bind to the 5’ cap?

Answer 9

through rRNA and amino acid interactions

Question 10

how does the ribosome bind to the Ribosome-Binding_Site

Answer 10

a sequence of rRNA is complementary (Base pairs) to the sequence of RBS)

Question 11

initiation factors

Answer 11

imitation factors recruit the small ribosomal subunit and tRNAmet and scan the mRNA for an AUG codon

Question 12

initiation of translation in eukaryotes

Answer 12

when the complex reaches an AUG, the large ribosomal subunit joins, the imitation factors are related, and a tRNA complementary to the next codon binds to the A site

Question 13

codon

Answer 13

set of 3 adjacent AA which code for an amino acid

Question 14

reading frame

Answer 14

the first codon read determines how each subsequent codon is read

Question 15

why do we call the genetic code redundant or degenerate?

Answer 15

because many AA are specified by multiple codons (wobble effect!!)

Question 16

three phases of translation

Answer 16

1. initiation - AUG recognized and Met established as the first AA
2. Elongation - AA are added to the peptide
3. Termination - stop codon is reached, no new aa is added, and polypeptide is released from the ribosome

Question 17

how do ribosomes move in translation

Answer 17

• 5’ to 3’
• ribosome moves down one codon
• puts the tRNA carrying the polypeptide into the P site and the now uncharged tRNA into the E site, where it is ejected
• new tRNA complementary to the next codon binds to the A site

Question 18

wobble effect

Answer 18

bases in the 3rd position (3’ side of the codon on the RNA) do not require as much specificity to bind

Question 19

directions that proteins are built

Answer 19

N – C

Question 20

Elongation

Answer 20

polypeptide transfers to the AA on the tRNA in the A site

Question 21

how fast can bacteria translate

Answer 21

~20 a second wowwwwww

Question 22

how does the ribosome recognize the correct tRNA?

Answer 22

• it doesn’t!!
• charged tRNAs are floating around the cytosol and diffuse in and out of the A site
• the ribosome has to “try” out each one – if the anti-codon matches the codon, it stays
• large amount of ribosomes carrying out translation at any time

Question 23

large subunit of ribosome binding sites

Answer 23

A (aminoacyl) site
P (peptidyl) site
E (exit) site

Question 24

Anticodon

Answer 24

three nucleotides that undergo base pairing with the corresponding codon
on tRNA

Question 25

Open reading frame

Answer 25

uninterrupted stretch of nucleotides that make up codons that code for amino acids

Question 26

elongation factors

Answer 26

proteins that obtain energy for Ribosome movement along the mRNA and the formation of the peptide bonds found to GTP molecules Break their high-energy bonds to provide energy for the elongation of the polypeptide

Question 27

process of translation in eukaryotes

Answer 27

one group of initaiton factors binds ot the 5' cap that is added to the mRNA during processing ○ Recruit a small subunit of the ribosome!! ○ Other initiation factors bring up tRNA charged with Met ○ Theeennnn moves along the mRNA until it find the first AUG § Position establishes the trnaslational reading frame ○ Large ribosomal subunit joins the complex!! § Initiation factors are released § Next tRNA is ready to join baybee

Question 28

process of translation in prokaryotes

Answer 28

- mRNA molecules have no 5' cap - Initiation process is formed at one or more internal sequences present in the mNRA known as a shine-dalgarno sequence - Ability to intitate translation internally allows projaryotic mRNAs to code for more than one protein

Question 29

shine-dalgarno sequence

Answer 29

where initiation process is formed in the mRNA for prokaryotes