protein translation

Question 1

features of mRNA

Answer 1

a

Question 2

features of tRNA

Answer 2

a

Question 3

features of ribosomes

Answer 3

a

Question 4

steps in translation

Answer 4

initiation
elongation
termination

Question 5

initiation of translation

Answer 5

tRNA carrying Met and eIF-2/GTP bind, forming ternary complex
small subunit binds ternary, guided by eIFs, forming pre-initiation complex
large subunit binds assembled complex, eIFs are lost, forming initiation complex

Question 6

elongation step of translation

Answer 6

binding of aminoacyl-tRNAs at A site
formation of peptide bond
translocation of peptidyl-tRNA to P site

Question 7

termination of translation

Answer 7

a

Question 8

polysomes

Answer 8

can be free or on rER

complex formed by multiple ribosomes attaching to single mRNA at same time

Question 9

antibiotics that inhibit protein synthesis in bacteria

Answer 9

streptomycin
tetracycline
chloramphenicol
erythromycin
neomycin and gentamycin

Question 10

toxins that inhibit eukaryotic protein synthesis

Answer 10

diphtheria toxin
ricin
shiga toxin

Question 11

protein folding

Answer 11

proteins require folding into 3D conformation in order to have biological activity
cytoplasmic proteins spontaneously fold themselves
others require chaperone proteins to assist in folding

Question 12

post-translation modifications

Answer 12

glycosylation
lipid addition
addition of other chemical groups (phosphorylation, acetylation, etc.)

Question 13

glycosylation

Answer 13

addition of carbohydrate to protein
begins in ER, moves to Golgi
glycosyltransferase transfers sugar from sugar donor to protein acceptor
formation of glycosidic bond
transferase is specific for sugar and protein
important in formation of recognition sites
N-linked and O-linked

Question 14

lipid addition

Answer 14

lipid groups are added to proteins that associate with membranes

Question 15

protein targeting

Answer 15

addition of amino acids or sugars in order to designate target of enzyme
allows transportation of enzyme to correct cellular compartment

Question 16

protein degradation

Answer 16

two paths: lysosomes or proteasomes

Question 17

cystic fibrosis

Answer 17

mutation in gene encoding CFTR
CFTR is misfolded and tagged for degradation in proteasomes
affects cells that secrete mucous and digestive juices
plugging of ducts and passageways

Question 18

I-cell disease

Answer 18

a

Question 19

alpha1 antitrypsin deficiency

Answer 19

a

Question 20

amino acid activation

Answer 20

a

Question 21

codon and anti-codon pairing

Answer 21

a

Question 22

streptomycin

Answer 22

binds 30S subunit

causes misreading of mRNA, preventing formation of initiation complex

Question 23

tetracycline

Answer 23

binds 30S

inhibits binding of initiator tRNA to A site

Question 24

chloramphenicol

Answer 24

binds 50S

inhibits peptidyl transferase activity of large subunit

Question 25

erythromycin

Answer 25

binds 50S

prevents translocation

Question 26

neomycin and gentamycin

Answer 26

cause misreading of mRNA

Question 27

diphtheria toxin

Answer 27

prevents translocation by inhibiting eEF-2

involves ADP-ribosylation of eEF-2

Question 28

ricin

Answer 28

N-glycosidase activity
catalyzes cleavage of adenine base from 28S rRNA
inhibits protein synthesis due to loss of I and E factors

Question 29

shiga toxin

Answer 29

inactivates 28S and 60S

similar mechanism as ricin

Question 30

gray baby syndrome

Answer 30

can result if infants are treated with chloramphenicol

don’t have enzyme to excrete drug

Question 31

chaperones

Answer 31

assist in folding of non-cytoplasmic proteins
bind hydrophobic regions of partially folded peptides, guide correct folding
in cytoplasm and ER

Question 32

heat shock proteins

Answer 32

HSPs
type of chaperone protein
repair proteins damaged by heat or stress
highly expressed in some cancers, leading to drug resistance
mutations in HSPs can cause misfolding disorders

Question 33

N-linked glycosylation

Answer 33

a

Question 34

O-linked glycosylation

Answer 34

a

Question 35

dolichol

Answer 35

a

Question 36

wobble hypothesis

Answer 36

some tRNAs can pair with more than one codon

why there are only 50 tRNAs