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Worksheet 6: Protein Synthesis

Multiple Choice and True or False

1. Which of the following statements about the genetic code is False?

A) The genetic code is not redundant and not ambiguousB) ach codon s!eci"es an amino acid.#) $here are %& di'erent ty!es of amino acids in a !rotein() one of the abo*e

%. Each group of __________ consecutive nucleotides in mRNA is called a _______ and specifies

one amino acid:+) Three, Anticodon

B) Three, Codon

#) $wo, codon() $wo, anticodon

-. Which of the following statements is True: A) Aminoacyl-tRNA synthetases recognize and attach the correct

amino acid to the tRNAB) +minoacylt/+ synthetases attach amino acids to t/+s *ia non

co*alent bonds.#) +ll amino acids ha*e the same aminoacylt/+ synthetase() The amino acid recognizes the appropriate codon on the mRNA

) All the above

4.  seudouridine, is a post!transcriptional modifications of RNA that:

A" #tabilizes the local tRNA structure$" %s found in all tRNA and rRNA but not in mRNA

&" destabilizes the RNA structure and ma'es it more fle(ible

D) both A&B are correct

E" both $)& are correct

0. ukaryotic m/+s:A) are translated ater they are e!ported rom the nucleus"B) are transcribed and translated simultaneously.#) must be folded into the correct threedimensional sha!e before they can

be translated.

() are !rocessed in the same way as !rokaryotic m/+s.

*. $efore mRNA can be translated, it is transported out of the nucleus into the c+toplasm via pores

called:

A) Nuclear pore complexes

$" mRNA pore comple(es

&" e(port pore comple(es" none of the above

-

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#" ow many nucleotides are necessary to s!ecify a single amino acid?A) 1B) %C) $%) %&

8. hich of the follo/ing statements about ribosomes is False?

A) #ome ribosomes are free in the c+tosol, others are attached to membrane surfaces of the rER 

B) The ribosome is not a ribo!me

&" Ribosomes are located in chloroplasts and mitochondria

D) None o" the abo#e

2. Within the ribosome, the formation of !e!tide bonds is cataly3ed by:+) aminoacylt/+synthetaseB) the tRNA itselC) an RNA molecule in the large ribosomal subunit

() a !e!tidase in the small ribosomal subunit.

&'" What is a !olyribosome?A) A cluster o ribosomes translating the same mRNA( but

positioned at dierent sites along the mRNA"B) + ribosome that is in the middle of translating an m/+ into a

!oly!e!tide.C) + ribosome translating a !olycistronic m/+ molecule.%) one of the abo*e

&&" Proteasomes act !rimarily on !roteins that ha*e been marked fordestruction by the co*alent attachment of which small !rotein?A) ProteaseB) ProteomeC) *bi+uitin%) istone

-0. roteins s+nthesized on 1free2 ribosomes are stabilized b+ covalent bonds and are bound to be

secreted out of the cell.

A) True

$" 3alse

Fill in the blan$s%

A ribosome contains t/o dissociable subunits: _____________ and ______________. These

subunits are a mi(ture of _________________ and _________________. Ribosomal proteins are

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made in the _________________, and then the+ are transported to the ______________to 5oin /ith

 ___________ to assemble the t/o ribosomal subunits.

The ribosome has four important binding sites for translation. The __________________ site is

/here the mRNA binds. 6nce bound, the _____________ site binds each ne/l+ arriving charged

tRNA and holds it until _______________ bond is formed /ith the carbo(+ end of gro/ing

 pol+peptide. To continue gro/th of the pol+peptide chain, the tRNA is then shifted to the

 ________________ site. 3inall+, the tRNA is shifted to the ________________site /here their

amino acids are discharged and it is released from the ribosome.

%e,ne the olloing:

#odon:

+nticodon:

+da!tor 4olecules:

/ibo3ymes:

Proteosome:

.hort Anser:

7ive t/o e(planations for ho/ RNA ma+ have preceded NA and proteins in evolution.

hat t+pes of proteins are involved in e(porting mRNA out of the nucleus8

0

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hat does the follo/ing statement mean: 1the code is redundant but not ambiguous28

hat does dih+drouridine contribute to tRNA8

9ist the three primar+ roles that ribosomes pla+ during protein s+nthesis

hat contribution has oachim 3ran' made to the mechanistic understanding of protein s+nthesis8

;an+ proteins re<uire additions or subtractions to the primar+ se<uence before the+ are useful to the cell.

A" efine post!translation modification and describe ho/ it is different from post!transcriptional

modifications

$" 9ist 0 post!translational protein modifications.

 Name and list the functions of the four sites on the ribosome involved in protein s+nthesis.

h+ are ribosomes and splisosomes thought of a riboz+mes but tRNA and mRNA not8

4

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