Protein Synthesis

Question 1

Name the three characteristics of the genetic code.

Answer 1

specific, universal, and degenerate

Question 2

aminoacyl tRNA and charging

Answer 2

hydrolysis of 2 ATP equivalents to charge

Question 3

Name the 3 steps of translation.

Answer 3

initiation, elongation, and termination

process similar in prokaryotes and eukaryotes except translation in prokaryotes is co-transcriptional

Question 4

Describe the formation of the pre-initiation complex.

Answer 4

eIF2 and eIF4 complexes bind

Question 5

Kozak sequence

Answer 5

a sequence recognized tby the ribosome to know where to start translation

in sequences that flank it, ATF are the preferred baces

Question 6

initiation complex

Answer 6

once eIF2 finds the correct site, it will hydrolyze its GTP into GDP and then initiates after ejecting the initiation factors

Question 7

Describe the process of elongation

Answer 7

kinetic proofreading - if eIF1alpha sits for long enough without forming the base pairs, the wrong tRNA is released and another one enters

Question 8

describe the process where EF1alpha is recycled

Answer 8

Question 9

Describe the initiation process in prokaryotes.

Answer 9

ribosomes are smaller, bacterial mRNA not capped, ATP uis not required

uses the Shine-Dalgarno sequence

Question 10

Describe the termination process in eukaryotes.

Answer 10

when there is a stop codon, a release factor binds to terminate translation.

Question 11

polysome

Answer 11

when many ribosomes are translating at the same time on an mRNA, approximately 100 nucleotides apart

Question 12

streptomycin

Answer 12

binds to 30S subunit of prokaryotic ribosomes distorting their structure and interfering with initiation

Question 13

tetracycline

Answer 13

binds to the 30S subunit of prokaryotic ribosomes and inhibits binding of aminoacyl-tRNAs to the A site

Question 14

puromycin

Answer 14

aminoacyl-tRNA analog and becomes incorporated into the polypeptide chain inhibiting elongation

Question 15

erythromycin and clarithromycin

Answer 15

bind to the P site of the 50S subunit of prokaryotic ribosomes and inhibits translocation

Question 16

chloramphenicol

Answer 16

interferes with the 50S ribosomal subunit of prokaryotes inhibiting peptidyl transferase activity

high levels are toxic in humans because it also inhibits human mitochondrial protein synthesis

Question 17

diphtheria toxin

Answer 17

inactivates EF-2 by catalyzing ADP-ribosylation preventing transliocation

even a little bit can be lethal to humans

Question 18

ricin

Answer 18

removes an adenine from eukaryotic 28S rRNA and inhibits ribosome function

Question 19

chaperone-assisted protein folding

Answer 19

help unfold stuck proteins and uses ATP as a source of energy to help overcome kinetic barriers

Question 20

enzyme-mediated modifications

Answer 20

addition of hydrophobic lipid groups for membrane localization

addition of cofactor for enzyme activity

addition of small chemical groups (mostly reversible)

Question 21

non-enzyme mediated modification

Answer 21

glycation - the addition of sugar

Question 22

proteostasis

Answer 22

the maintenance of the proteosome of the cell, correct combinations of all the different proteins are improtant for function

on-pathway intermediates are partially folded proteins

Question 23

two reasons for degradation of intracellular proteins

Answer 23

removal of uneeded proteins in response to physiologic demand

removal of proteins damaged by mutation, oxidation, and other modifications

Question 24

lysosome degradation

Answer 24

mainly deal with things that come fromt he outside of the cells

fusion with endocytic tissues, degradation of proteins through directy targeting, autophagy of organelles and protein aggregates

Question 25

chaperone mediated autophagy (CMA)

Answer 25

use LAMP2A channel

Question 26

microautophagy

Answer 26

when lysosomes engulf molecules in bulk or slective ly through hsc70 interactions

Question 27

microautophagy of organelles

Answer 27

phagophore formation int he ER

Question 28

ubiquitin proteosome system

Answer 28

polyubiquitination targets protein for degradation

only one E1 that actis with a few dozen E2s, each one with a few dozen E3s

amplifcation of signal to specific proteins

Question 29

cytoplasmic mis-folded protein response

Answer 29

fold, hold or degrade

chaperones are the first linke of defense, failure to fold leads to targeting for degradation

accuulation forms aggregates that can lead to amyloid

Question 30

four types of conditions that can lead to protein aggregation

Answer 30

mutations in proteins or in the quality control system

defects in translation and assembly into protein complexes

environmental stress: heat, oxidative stress

aging: increased oxidative stress and reduced capacity to remove misfolded proteins