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Bio 113 Lecture 7
Translation
52
Biology
Undergraduate 1
01/31/2013

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Term
during transcription which direction is mRNA made in?
Definition

5" to 3"

 

remember transcription is the synthesis of mRNA

Term
during translation which direction is mRNA translated?
Definition

mRNA is also translated in the 5" to 3" direction

 

translation is when mRNA is used to make a polypeptide chain

Term
during translation which direction is the polypeptide chain made?
Definition
N terminal to the C terminal
Term
in preparation for translation which 4 things are needed?
Definition

adaptor molecules -tRNA

specific activating enzymes

amino acids

ribosomes

Term
which 3 ways can a tRNA molecule be depicted?
Definition

as 2d clover leaf

as 3d l shaped

as a simplified dynamite stick

Term
how many codons are there?
Definition
64 but 61 are amino acid codons and there are 3 stop codons
Term
what is the difference between the activating enzymes and the tRNA for the amino acids?
Definition
there are one activating enzyme for each amino acid but on 40 different tRNA for the 61 amino acids
Term
how is the issue with 40 tRNA molecules per 61 amino acids solved?
Definition
most amino acids are specified by more than one codon, differing in the 3rd position. this enables the use of fewer tRNAs than the number of codons
Term
what is the name of the unusual base pairing interaction between codon and anticodon called?
Definition
wobble
Term

wobble rules

 

which position does the wobble rule affect on the codon and the anti codon?

Definition

third 3" position on the codon

first 5" position on the anti codon

Term

Wobble rules

 

U Can Go

 

explan

Definition

3" codon U or C

5" anti codon G

Term

wobble rules

 

Giving Care

 

explain

Definition

3" codon G

5" anticodon C

Term

wobble rules

 

U Ass

 

explain

Definition

3" codon U

5" anti codon A

Term

wobble rules

 

A Girl Unicorn

 

explain

Definition

3" codon A or G

5" anti codon U

Term

wobble rules

 

U C Anything Interesting?

 

explain

Definition

3" codon U, C or A

5" codon I 

 

tRNA contains Inosine

Term
which unique base does tRNA contain?
Definition

Inosine

 

pairs with a U, C or A 3" codon

Term
what is the process of charging a tRNA with its cognate amino acid called?
Definition
amino acylation
Term
which enzyme is involved in tRNA charging?
Definition
Aminoacyl-tRNA synthetase
Term
what also happens in the first step when an amino acid binds to the tRNA synthetase?
Definition
ATP also binds. it loses two Pi and binds as AMP adenosine monophosphate.
Term
what happens during the covalent bonding of tRNA to the amino acid?
Definition
the AMP gets displaced. the enzyme then releases the activated aminoacyl tRNA.
Term
what type of bond forms between the tRNA and the amino acid?
Definition
a covalent bond
Term
during polypeptide synthesis which organelle helps in the formation of peptide bonds?
Definition
ribosomes
Term
which 2 components are ribosomes composed of?
Definition
proteins and rRNA (ribosomal RNA)
Term
how many subunits does an active ribosome contain?
Definition
2 , a large and a small one
Term
which subunit of an rRNA would you find the binding site for mRNA?
Definition
the small one
Term
how many binding sites does the large ribosomal subunit have? and what binds to these?
Definition

it has 3 binding sites. from left to right these are EPA and tRNA binds to these.

 

E = exit site

P = Peptidyl site

A = aminoacyl site

Term
name the 3 steps in translation of mRNA
Definition

Initiation

Elongation/translocation

Termination

Term

eukaryotic mRNA has a unique 3" end. what is this called?

what cap would you find at the 5" end?

Definition

the Poly A tail is found at the 3" end

the 5" end has a methylated cap

Term
when does initiation begin?
Definition
when the small unit of the ribosome attaches to the methylated cap and moves to the translation initiation site.
Term
what is typically the first mRNA codon?
Definition

AUG - codes for methionine, a start codon

the anti codon would be UAC

Term
during elongation which binding site on the large unit of the ribosome does the charged tRNA molecule bind to?
Definition
 it binds to the aminoacyl binding site. the polypeptide chain it then peptide bonded to the incoming charged tRNA. this then moves to the P site and the one that was in the P site has now moved to the E (exit) site and been relased
Term
what codon is needed for a relase factor to enter the A site of the large ribosomal subunit and what does this do?
Definition
a stop codon is needed for a release factor to enter the A site. This terminates translation
Term
which two stages in tanslation require energy and how is this derived?
Definition
code recognition (elongation) and translocation need energy. this is derived from GTP to GDP
Term
between which functional groups is a peptide bond formed? is anything produced during peptide bond formation?
Definition

between the carboxyl group of one amino acid and the amino group of the following one.

a molecule of h20 is formed during the formation of a peptide bond

Term
UAA, UGA, UAG are AKA?
Definition

Stop codons

 

AUG is aka a start codon

Term
a mRNA is generally translated simultaneously by several ribosomes in clusters. what is this known as?
Definition
Polyribosomes
Term
the major differences in translation between eukaryotic and prokaryotic arise from what feauture in eukaryotic cells?
Definition
compartmental organisation in eukaryotic cells
Term

which kingdom of cell can transcribe and translate the same gene simultaneously? 

Definition
Prokaryotes. New protein diffuses to its operating site. 
Term
which part of a cell segregates transcription from translation and whats happens during this time?
Definition
the nuclear envelope segregates transcription from translation and during this time RNA processing takes place.
Term
eukaryotic cells have to lots of ribosomes. what are they and where are they found?
Definition
free and bound. free ones found in cytosol and the bound ones found attached to cytosolic side of the endoplasmic reticulum
Term
which side of the ER are bound ribosomes found?
Definition
the cytosolic side
Term
where does translation begin?
Definition
in the cytosol
Term
a polypeptide destined for the ER or export will have a signal peptide. what is this and where is it found on the polypeptide?
Definition
it is a chain of about 20 amino acids long and found near the N terminus. helps direct signal recognition particle (SRP) to take the polypeptide to its destination
Term
what happens when a SRP binds to the specific signal peptide?
Definition
takes the polypeptide and its ribosomes and attaches it to a signal receptor protein in the ER membrane. the signal peptide is then cleaved
Term
do signal peptides only go to the ER?
Definition
no. specific signal peptides target polypeptides to mitochondria, chloroplast, nucleus and other organelles not part of the endomembrane system.
Term
where is the signal cleaving enzyme that removes the signal peptide found?
Definition
in the signal receptor protein bound to the ER. it also has a membrane pore that allows the polypeptide chain through into the ER
Term
which antibiotic inhibits the formation of peptide bonds?
Definition
chloromycetin
Term
which antibiotic inhibits the translocation of mRNA along the ribosome?
Definition
erythromycin
Term
which antibiotic inhibits interactions between tRNA and mRNA?
Definition
neomycin
Term
which antibiotic inhibits initiation of translation?
Definition
streptomycin
Term
which antibiotic inhibits binding of tRNA to ribosome?
Definition
Tetracycline
Term
what does peptidyl transferase do?
Definition
catalyse the formation of peptide bonds
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