Protein Synthesis- Lecture 8/23/21

Question 1

Components to amino acids

Answer 1

Central carbon surrounded by a carbonyl group, amino group, and 20 distinct R groups

Question 2

Ribosomes

Answer 2

Sites of polypeptide synthesis-> 2 subunits that are 60S and 40 S

Question 3

rRNA lengths

Answer 3

Large subunit- has 28 S, 5.8 S, 5 S

Small subunit- 18S

Question 4

UTR

Answer 4

Either 5’ or 3’ untranslated region 3’ determines the stability of the mRNA and the 5’ plays a regulatory role

Question 5

Codon

Answer 5

Groups of three bases that encode for an amino acid

Question 6

Degenerate code

Answer 6

For most amino acids, the tRNA anticodon recognizes more than one “code word”

Question 7

tRNA

Answer 7

Clover shaped RNA that carries amino acid to correct site of the mRNA. Cargo loaded at the 3’ site

Question 8

tRNA modifications

Answer 8

CCA sequence at the 3’ terminal added, amino acid attached at the 3’ end via covalent linkage from its carbonyl end

Question 9

Aminoacyl-tRNA synthetases

Answer 9

Adds the correct amino acid on the tRNA, recognizes anticodon region. About 20 aminoacyl-tRNA transferases for each amino acid

Question 10

Anti-codon

Answer 10

Recognizes the codon and binds 3’->5’ against the codon 5’->3’

Question 11

Wobble hypothesis

Answer 11

Anticodons can recognize more than one codon because the recognition between the 3’ base of the codon and 5’ base if anti-codon is weaker

Question 12

eIF2

Answer 12

Eukaryotic initiation factor, binds to the GTP and Met-tRNA with the 40S subunit to initiate translation

Question 13

EIF4

Answer 13

Recognizes the 5’ cap to bring the eIF2,tRNA,40S subunit to the mRNA

Question 14

Translation start

Answer 14

Scans to find the initiation codon, once ther eIF2 is released and adds 60 S subunit

Question 15

Ribosomes 3 sites

Answer 15

A-> acyl site (new one coming in again)
P-> Peptidyl site contains the tRNA complex with all the peptides added
E-> exit, empty tRNA

Question 16

EF1

Answer 16

next tRNA is chaperoned in by elongation factor 1, energy from hydrolysis of GTP, moved from one site to another

Question 17

Translocation

Answer 17

Whole unite moved to the next place by EF2 and GTP

Question 18

Peptidyl-transferase

Answer 18

A component of 28S RNA which catalyzes the formation of a peptide bond

Question 19

Termination of synthesis

Answer 19

once the stop codon is reached, a release factor comes and catalyzes the disassociation of the subunit using GTP energy

Question 20

Stop codon

Answer 20

UAG, UAA, UGA

Question 21

polyribosomes

Answer 21

In prokaryotes, one mRNA can be translated by multiple ribosome complexes

Question 22

Missense mutation

Answer 22

When a point mutation changes one amino acid at a given position

Question 23

A nonsense mutation

Answer 23

When a stop codon is erroneously added/taken away by mutation which leads to a significantly longer/shorter protein product

Question 24

Frame-shift mutation

Answer 24

When there is a one base deletion which changes the entire peptide product from that point forwar

Question 25

Phosphorylated eIF2

Answer 25

When the cell is in stress, it will phosphorylate eIF2 which turns it off thereby turning off gene translation

Question 26

MicroRNA (miRNA)

Answer 26

Naturally occurring double stranded mRNA that can bind to 3’ UTR which leads to RISC complex and degradation when perfect homology and blocks translation when imperfect but close