1. Transcription and Translation The How to…
Protein Synthesis
Transcription and Translation
The How to…

2. Why Proteins are Important
The goal of any cell at any given moment is to produce chains of proteins.
These proteins are used to dictate directions and functions of the cell.

3. The amount of proteins to make, the type of proteins to make and when those proteins are to be made is dictated by the DNA of the cell.

4. Amino acids: the building blocks of proteins
Proteins are made from many amino acids.
The sequence of nitrogenous bases in DNA is the “code” that tells cells what amino acids to produce
There are 20 different amino acids that are commonly found in proteins
Every 3 nitrogenous bases code for an amino acid

5. Try This…
Using your codon chart, find the sequence(s) of the following amino acids:
Alanine:
Histidine:
Leucine:

6. Amino acids: the building blocks of proteins
simple atomic structure:
Central carbon atom bound to:
1 carboxyl group (COOH)
1 amino group (NH2)
1 hydrogen atom
1 side chain represented by “R” (meaning it is different in every amino acid)

8. Amino acids bond together by dehydration synthesis.
Peptide bond forms between the amino group of one molecule and the carboxyl group of another.
Resulting molecule is called a dipeptide

9. Polypeptide: multiple dipeptides bonded together
Proteins: multiple polypeptides bonded together
smallest protein = 50 amino acids
Largest protein = amino acids
Each different sequence of amino acids codes for a different protein
Sections of folded chain will bond together to form cross-links
Different shapes can therefore code for different proteins

10. Proteins A-A-A-C-G-C-G-A…. Dipeptide Polypeptide (1 or more)
Amino acid + Amino acid + Amino acid…
Dipeptide
Polypeptide (1 or more)
Proteins

11. Today scientists know that genes are made of many nucleotides.
The order of the bases codes for the amino acids that will be added to the polypeptide chain.
The order will vary among different species but will be similar among members of the same species.

12. URACIL instead of THYMINE
Protein synthesis:
1) TRANSCRIPTION: takes place in the nucleus
copies the DNA code for a polypeptide into a molecule of RNA.
The DNA strand separates for a short time to serve as a template (or pattern) for RNA.
Complimentary RNA nucleotides take their place on the DNA strand
Just like when DNA replicates, with one difference
URACIL instead of THYMINE
A-A-A-C-G-A-T-A-T-T-G-C-C-G-A A A U U U G C U A U C G G C U

13. When the RNA reaches a specific “STOP” code (a code of Nucleic acids e
When the RNA reaches a specific “STOP” code (a code of Nucleic acids e.g. UAC) it leaves the DNA strand.
The RNA strand is now a separate molecule that carries the complete code for one Polypeptide
The involved RNA in this step is known as messenger RNA or mRNA

16. 2) TRANSLATION: code amino acids
Once mRNA has copied the code, the next step is to actually create the polypeptides.
Transfer RNA tRNA
There are 20 different kinds of tRNA, one for each amino acid
The have a short tail on one end that can “pick up an amino acid”
Each tRNA can carry only one specific amino acid

17. tRNA At the base is an Anticodon. that complements the mRNA code
This is how the tRNA knows
Which amino acid to pick up.

20. Once the protein is made, it will either:
Once the amino acids are lined up, they will go through dehydration synthesis to become a complete protein.
Once the protein is made, it will either:
Stay in the cell and be used to instruct organelles on their function.
Be transferred to another cell to communicate information between 2 cells.