1. Protein Synthesis

2. DNA’s Function DNA is the genetic material of all living things
It carries the ‘instructions’ necessary for life
DNA “controls the cell’s functions” by controlling the synthesis of proteins in the cell
These proteins may be:
Enzymes that control chemical reactions
Cell membrane proteins such as transport proteins that control what enters or leaves the cell.
Hormones (such as insulin)
Antibodies that fight diseases
Structural proteins such as muscles and bone proteins
DNA’s Function

3. Protein Review Just a quick refresher… Proteins are a polymer
The monomer of proteins are amino acids
Amino acids connect to make peptides
Peptides twist, bend, and combine to make proteins
There are 20 different amino acids used by DNA to build proteins
Amino Acids make peptide chains
The folding of peptide chains makes proteins

4. Protein Review Proteins are made of amino acids
The protein twists, attracts, and bends into specific shapes based on what amino acids make it up
The shape of the protein allows it to perform the job that it completes

5. Function of Proteins
Collagen Proteins (Structural)
Vital for building, repair and maintenance of cells and tissues (including nerves, muscles, skin, hair)
Globular Proteins (Physiological Roles)
Enzymes, Used for movement and transportation in and of the body, certain Hormones, Antibodies, and as an Energy Source (like carbohydrates).

6. One Gene One Polypeptide Hypothesis
A gene is a sequence of DNA that codes for a single protein (polypeptide)
Genes have the information required to build one particular protein
Since each protein is made of a specific sequence of amino acids, each protein will have its own characteristics.

7. The process: Proteins are organized by the ribosome
The ribosomes take amino acids that you have eaten and reassemble them to match the code from your DNA to make the protein.
This process is called PROTEIN SYNTHESIS.

8. The players in protein synthesis
DNA
RNA
mRNA
rRNA
tRNA
Ribosomes
Amino acids
Proteins

9. Central Dogma of Molecular Biology
Information flows in one direction from DNA to RNA to proteins.
DNA can pass information to DNA, RNA, or Proteins.
Proteins cannot pass information to other proteins.
This idea is call the Central Dogma of Molecular Biology

10. Replication Transcription Translation
The central dogma includes three processes.
Replication
Transcription
Translation
replication
transcription
translation
RNA is a link between DNA and proteins.

11. RNA differs from DNA in three major ways.
RNA has a ribose sugar.
RNA has uracil instead of thymine.
RNA is a single-stranded structure.

12. Why Uracil? RNA is likely evolutionary older than DNA
Thymine gives more stability to DNA. It does not break down as easy due to the structure of Thymine.
RNA is an easily degradable molecule which needs to be produced continuously
DNA is more resistant to degradation in the long term.

13. Steps to Protein Synthesis
Transcription (in the Nucleus of Eukaryotes)
Information from a gene (part of the DNA) is coded into mRNA (messenger RNA)
DNA is transcribed into the language of RNA
Translation (at the Ribosome)
The mRNA information is then translated by the ribosome.
The ribosome then takes the information and makes the protein.
RNA is translated into the language of proteins

14. KEY CONCEPT Transcription converts a gene into a single-stranded mRNA molecule.
-Transcription – rewrite – DNA will be rewritten into RNA

15. The Stages of Transcription
Transcription will happen in 3 stages:
Initiation
Elongation
Termination

16. Initiation RNA Polymerase binds to the DNA at the TATA Box or Promoter
RNA Polymerase unwinds the DNA

17. The TATA Box and Promoters
DNA Transcription TENDS TO start at the TATA Box.
The TATA box is a specific sequence of DNA that shows the cell where to begin making converting DNA into RNA
It is normally: TATAAA
The DNA may also start from a site called the Promoter

18. Elongation RNA Polymerase reads the unwound section of DNA
As RNA Polymerase reads the DNA it also creates a piece of RNA to match the code
RNA Polymerase slides forward along the DNA and makes a longer section of RNA

19. Termination
RNA Polymerase will encounter a section of DNA called the Terminator
This is a signal for the RNA polymerase to leave the DNA and stop building the RNA section

20. Transcription Summary

21. Transcription makes two important types of RNA.
Messenger RNA (mRNA) carries the message that will be translated to form a protein.
Transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome.

22. KEY CONCEPT Translation converts an mRNA message into a polypeptide, or protein.

23. The genetic code matches each codon to its amino acid or function.
three stop codons
one start codon, codes for methionine

24. Amino acids are coded by mRNA base sequences.
Translation converts mRNA messages into proteins.
A codon is a sequence of three nucleotides that codes for an amino acid.
codon for
methionine (Met)
leucine (Leu)

25. A change in the order in which codons are read changes the resulting protein.
Regardless of the organism, codons code for the same amino acid.

26. Amino acids are linked to become a protein.
An anticodon is a set of three nucleotides that is complementary to an mRNA codon.
An anticodon is carried by a tRNA.

27. Ribosomes consist of two subunits.
The large subunit has three binding sites for tRNA.
The small subunit binds to mRNA.

28. 1. For translation to begin, tRNA binds to a start codon and signals the ribosome to assemble.
2. A complementary tRNA molecule binds to the exposed codon, bringing its amino acid close to the first amino acid.

29. 3. The ribosome helps form a polypeptide bond between the amino acids.
4. The ribosome pulls the mRNA strand the length of one codon.

30. 5. The now empty tRNA molecule exits the ribosome.
6. A complementary tRNA molecule binds to the next exposed codon.
7. Once the stop codon is reached, the ribosome releases the protein and disassembles.