Download Protein Synthesis Notes

AN OVERVIEW OF PROTEIN SYNTHESIS
The making of proteins is called PROTEIN SYNTHESIS. The sequence of DNA bases is a code for protein
synthesis. Before we explore the method of how proteins are made, it is necessary to introduce another type of
nucleic acid- RNA.
RNA stands for ____________________________________________________
RNA differs from DNA in four ways:
1. _______________________________________________________________________________________
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2. _______________________________________________________________________________________
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3. _______________________________________________________________________________________
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4. _______________________________________________________________________________________
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Cells contain three types of RNA: explain their roles
1. _______________________________________________________________________________________
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2. _______________________________________________________________________________________
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3. _______________________________________________________________________________________
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Protein synthesis occurs in 2 steps:
STEP 1- ___________________________________________________
WHERE IT OCCURS- ___________________________________________________
OVERALL FUNCTION- ___________________________________________________
DESCRIPTION OF EVENTS- A small part of the DNA molecule unzips and RNA nucleotides bind to the
complimentary bases on the exposed DNA strand. It is important to note that when there is an exposed
ADENINE base on the DNA molecule, a URACIL base of RNA will bind with the ADENINE (U binds with
A- refer to picture). This newly formed RNA strand is the messenger RNA molecule.
Each combination of three bases in the mRNA strand is called a CODON (a three letter code for a particular
amino acid). Remember that amino acids are subunits for proteins. Each codon codes for a specific amino acid.
For example, the codon GUA codes for the amino acid VALINE; the codon UCA codes for the amino acid
SERINE.
Once the mRNA strand is formed, it separates from the original DNA molecule and moves into the cytoplasm.
It is now time for the next step in protein synthesis.
STEP 2- ___________________________________________________
WHERE IT OCCURS- ___________________________________________________
OVERALL FUNCTION- ___________________________________________________
DESCRIPTION OF EVENTS- The messenger RNA has traveled from the nucleus
to the cytoplasm where it attaches to a ribosome. Here, each mRNA codon attaches
to a transfer RNA molecule. The tRNA molecule is a single strand of RNA that
loops back on itself. At one end it has 3 bases called an ANTICODON, At the
other end the corresponding amino acid is attached. The CODON of the mRNA
attaches to the ANTICODON of the tRNA molecule. For example, if the mRNA
codon is UAC, it will attach to a tRNA molecule which has the anticodon of AUG.
As the tRNA molecules line up and bind to the mRNA molecule, the amino acids
are placed in proper order to form a specific protein. PEPTIDE BONDS form
between each amino acid and eventually they break away from the tRNA molecule.
The tRNA molecule can then be used again.
If we trace an individual amino acid of a protein molecule from the original DNA molecule it would look
something like this: (fill in the rest
Original DNA sequence-
AGT
CAT
CGC
ACT
mRNA codon-
UCA
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_________
tRNA anticodon-
AGU
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_________
_________
amino acid for AGU-
SERINE
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