Download Protein Synthesis 1 OBJECTIVES To understand how a cell

Biological Principles
Lab: Protein Synthesis
Name: ___________________________________
OBJECTIVES
 To understand how a cell manufactures proteins from amino acids, using information
stored in the genetic code.
 To assemble models of four very short proteins based on four mRNA sequences.
 To identify several types of mutations and to evaluate their impact on protein synthesis.
INTRODUCTION
The structure and operation of the human body (as well as all other organisms) is based on proteins.
Everything from skin and bones to hair, muscle and internal organs are constructed from proteins. The
enzymes that digest food and the hormones that regulate metabolism are all proteins. Although some of
these compounds are highly specialized and have additional materials associated with them (e.g.,
calcium found in bone tissue), all have proteins as their foundation.
MATERIALS
 Protein synthesis kit. This kit consists of 24 amino acids, 24 transfer RNAs, four messenger
RNAs and one ribosome.
anticodon
tRNA
ribosome
amino acid
mRNA
mRNA-amino acid conversion chart:
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PROCEDURE
1. Pair up your tRNA molecules with the appropriate amino acids.
2. Chain initiation. Insert the 5’ end of an mRNA into the ribosome until the first codon (AUG) is exposed
in the peptidyl-tRNA binding site. Select the tRNA with an anticodon that base-pairs with the exposed
codon and join it to the mRNA.
tRNA
amino acid
3. Chain growth.
a. The next codon is exposed in the amino acyl-tRNA binding site. Again, select an appropriate
tRNA with its attached amino acid and join it to the mRNA.
b. The amino acid (or peptide) that is presently joined to the tRNA at the peptidyl-tRNA binding site
is separated from the tRNA and joined instead to the amino group of the amino acid positioned at
the amino acyl-tRNA binding site. The result is a peptide bond between the two amino acids. The
free tRNA is released from the peptidyl-tRNA binding site and floats away.
c.
The ribosome now slides down the mRNA three nucleotides exposing the next codon in the
amino acyl-tRNA binding site.
d. Repeat steps a-c until the “protein” is synthesized (you reach the end of the mRNA).
4. Record the amino acid sequences for this “protein” in the observation section of the report.
5. Repeat this procedure with the other three mRNAs.
6. Answer the questions in the lab report.
7. Return all parts to the envelope and return to the instructor’s bench.
Note: The third base on some of the tRNA anticodons has been modified to inosine (I), which can pair
with U, C or A.
Adapted from Elements of Protein Synthesis by Thomas Peter Bennett,
W.H. Freeman and Company, 1969.
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