The document discusses various aspects of translation, including: 1. Initiation of translation involves assembly of mRNA, tRNA, and ribosomal components. 2. Synthesis of the polypeptide involves repeated cycles of amino acid attachment and ribosomal movement along the mRNA. 3. Termination occurs when a stop codon enters the ribosomal active site, causing disassembly of the translation components.

1. Essential idea: Information transferred from DNA to mRNA is
translated into an amino acid sequence.
7.3 Translation
Section of Titin, our largest known protein
http://circ.ahajournals.org/content/124/8/876/F2.large.jpg

2. Understandings
Statement Guidance
7.3 U.1 Initiation of translation involves assembly of the
components that carry out the process.
Examples of start and stop codons are
not required.
7.3 U.2 Synthesis of the polypeptide involves a repeated cycle of
events.
7.3 U.3 Disassembly of the components follows termination of
translation.
Names of the tRNA binding sites are
expected as well as their roles.
7.3 U.4 Free ribosomes synthesize proteins for use primarily within
the cell.
7.3 U.5 Bound ribosomes synthesize proteins primarily for
secretion or for use in lysosomes.
7.3 U.6 Translation can occur immediately after transcription in
prokaryotes due to the absence of a nuclear membrane.
7.3 U.7 The sequence and number of amino acids in the
polypeptide is the primary structure.
7.3 U.8 The secondary structure is the formation of alpha helices
and beta pleated sheets stabilized by hydrogen bonding.
7.3 U.9 The tertiary structure is the further folding of the
polypeptide stabilized by interactions between R groups.
Polar and non-polar amino acids are
relevant to the bonds formed between
R groups.
7.3 U.10 The quaternary structure exists in proteins with more than
one polypeptide chain.
Quaternary structure may involve the
binding of a prosthetic group to form a
conjugated protein.

3. Applications and Skills
Statement Utilization
7.2 A.1 tRNA-activating enzymes illustrate enzyme–substrate
specificity and the role of phosphorylation.
7.3 S.1 Identification of polysomes in electron micrographs of
prokaryotes and eukaryotes.
7.3 S.2 The use of molecular visualization software to analyze the
structure of eukaryotic ribosomes and a tRNA molecule.

4. Components of Translation
1. mRNA = message
2. tRNA = interpreter
3. Ribosome = site of translation
7.3 U.1 Initiation of translation involves assembly of the components
that carry out the process.

5. tRNA
• Transcribed in nucleus
• Specific to each amino acid
• Transfer AA to ribosomes
• Anticodon: pairs with
complementary mRNA codon
• Base-pairing rules between 3rd
base of codon & anticodon are
not as strict. This is called
wobble.
7.3 U.1 Initiation of translation involves assembly of the components
that carry out the process.

6. Ribosomes
• Ribosome = rRNA + proteins
• made in nucleolus
• 2 subunits
7.3 U.1 Initiation of translation involves assembly of the components
that carry out the process.

7. The role of RNA in Protein Synthesis
• 3 Types of RNA molecules in the steps from gene to
protein:
1. Messenger RNA (mRNA), Complementary copy of DNA
2. Transfer RNA (tRNA) carries amino acid to the site of
synthesis.
3. Ribosomal RNA (rRNA), stabilizes the site of synthesis
7.3 U.1 Initiation of translation involves assembly of the components
that carry out the process.

8. Translation stages:
Initiation, Elongation and Termination
• Translation occurs in the 5' to 3' direction along the mRNA
A. Initiation begins with the attachment of the ribosome to the mRNA
B. Elongation begins at the mRNA start codon AUG and continues
with the addition of amino acids to the polypeptide.
C. Termination occurs at the STOP codon (UGA, UAG or UAA).
7.3 U.1 Initiation of translation involves assembly of the components
that carry out the process.

10. Ribosomes
Active sites:
• A site: holds AA to be
added
• P site: holds growing
polypeptide chain
• E site: exit site for
tRNA
7.3 U.1 Initiation of translation involves assembly of the components
that carry out the process.

11. 7.3 U.2 Synthesis of the polypeptide involves a repeated cycle of events.
• While the first tRNA is still
attached, a second tRNA
attaches to the mRNA at
the A site on the ribosome,
carrying the amino acid
that corresponds to the
mRNA codon.
• The methionine amino
acid (Met) is the start code
for all amino acids, is the
first tRNA to arrive at the P
site binds to the amino
acid carried by the second
tRNA located at the A site.

12. 7.3 A.1 tRNA-activating enzymes illustrate enzyme–substrate specificity
and the role of phosphorylation.
• Each tRNA binds with a
specific amino acid in the
cytoplasm in a
reaction catalyzed by a
specific tRNA-activating
enzyme.
• Each specific amino acid binds
covalently to the 3'- terminal
nucleotide (CCA) at the end of
the tRNA molecule.
• The binding of the specific
amino acid to the tRNA
requires energy from ATP.
Bioninja

13. 7.3 A.1 tRNA-activating enzymes illustrate enzyme–substrate specificity
and the role of phosphorylation.
http://www.phschool.com/science/biology_place/biocoach/translation/addani.html

14. 7.3 U.2 Synthesis of the polypeptide involves a repeated cycle of events.
• The two amino acids are
joined together through
a condensation
reaction that creates
a peptide bond between
the two amino acids.
• The ribosome moves along
the mRNA one codon
shifting the tRNA that was
attached to methionine to
the E site.
• The tRNA is released back
into the cytoplasm from the
E site, allowing it to pick up
another amino acid
(methionine) to build
another polypeptide.

15. 7.3 U.2 Synthesis of the polypeptide involves a repeated cycle of events.
• Another tRNA moves into the
empty A site bringing the next
amino acid corresponding to
themRNA codon.
• Again, the amino acid is attached
to the polypeptide forming a
peptide bond, the ribosome slides
across one codon and tRNA at the
P site moves into the E site
releasing it back into the
cytoplasm.
• The ribosome continues to move
along the mRNA adding amino
acids to the polypeptide chain.
• This process continues until a stop
codon is reached.

16. 7.3 U.3 Disassembly of the components follows termination of
translation.
• Termination begins
when 1 of the 3 stop
codons
 UAA
 UGA
 UAG
moves into the A site.
• These tRNA have no
attached amino acids.
• When the stop codon
is reached
the ribosome
dissociates and the
polypeptide is
released.

17. http://highered.mheducation.com/sites/0072507470/st
udent_view0/chapter3/animation__how_translation_w
orks.html
http://www.stolaf.edu/people/giannini/flashanimat/molgen
etics/translation.swf
Watch these animations about the process of translation. Can you narrate?

18. 7.3 U.4 Free ribosomes synthesize proteins for use primarily within the
cell.
https://www.studyblue.com/notes/note/n/molecular-exam-3/deck/2630328
• Free ribosomes in the
cytoplasm synthesize
proteins that will be
used inside the cell in
the cytoplasm,
mitochondria and
chloroplasts (in
autotrophs)

19. 7.3 U.5 Bound ribosomes synthesize proteins primarily for secretion or
for use in lysosomes.
• Ribosomes attached to ER create
proteins that are secreted from the
cell by exocytosis or are used in
lysosomes.
• Proteins that are destined to be
used in lysosomes, ER, Golgi
Apparatus, the plasma membrane
or secreted by the cell are made by
ribosomes bound by the
endoplasmic reticulum
• Ribosomes that become bound to
the ER are directed here by a signal
sequence that is part of that
specific polypeptide
• This signal sequence on the
polypeptide binds to a signal
recognition protein (SRP)
• The SRP guides the polypeptide and
ribosome to the ER where it binds
to an SRP receptor http://herbmitchell.info/Figure.4-8-Synthesissecretoryprotein.jpg

20. 7.3 U.6 Translation can occur immediately after transcription in
prokaryotes due to the absence of a nuclear membrane.
• Since prokaryotic DNA is not compartmentalized into a nucleus, once transcription
begins creating a strand of mRNA, translation can begin immediately as the mRNA
strand is created
• In eukaryotes, the completed mRNA has to be transported from the nucleus,
through the nuclear pore to the ribosome on the ER or in the cytosol
http://www.mun.ca/biology/scarr/iGen3_05-09_Figure-L.jpg

21. Prokaryotes vs. Eukaryotes
Prokaryotes Eukaryotes
• Transcription and
translation both in
cytoplasm
• DNA/RNA in cytoplasm
• RNA poly binds directly to
promoter
• Transcription makes mRNA
(not processed)
• No introns
• Transcription in nucleus;
translation in cytoplasm
• DNA in nucleus, RNA travels
in/out nucleus
• RNA poly binds to TATA box
& transcription factors
• Transcription makes pre-
mRNA  RNA processing 
final mRNA
• Exons, introns (cut out)
7.3 U.6 Translation can occur immediately after transcription in
prokaryotes due to the absence of a nuclear membrane.

22. Structure of Proteins
The complex structure of
proteins is explained by
referring to 4 levels of
organization
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
http://upload.wikimedia.org/wikipedia/commons/2/26/225_Peptide_Bond-01.jpg

23. Structure of Proteins
Primary structure:
• The order/ number of amino acids in a polypeptide chain.
• Linear shape (no internal bonding)
7.3 U.7 The sequence and number of amino acids in the polypeptide is
the primary structure.

24. 7.3 U.8 The secondary structure is the formation of alpha helices and
beta pleated sheets stabilized by hydrogen bonding
Secondary Structure:
Hydrogen bonding causes
The primary structure of the
polypeptide to fold and coil
Into some characteristic
ways:
• Alpha Helix
• Beta pleated sheets

25. Beta-pleated sheets:
• Flat, zig-zag structure
• A number of chains which are hydrogen bonded together
• Forms a sheet
Example: Fibers in in silk
7.3 U.8 The secondary structure is the formation of alpha helices and
beta pleated sheets stabilized by hydrogen bonding

26. Changes to the primary and secondary
structure comes from additional bonds
Folding in the primary structure is
caused by charged groups on the
amino acid chain.
These charged groups include:
» Hydrogen bonds
» Ionic bonds
» Covalent bonds.
(disulphide bridge)
7.3 U.9 The tertiary structure is the further folding of the polypeptide
stabilized by interactions between R groups.

27. • Tertiary structure is the three-dimensional conformation
of a polypeptide.
• The polypeptide folds just after it is formed in
translation.
• The shape is maintained by intermolecular bonds
7.3 U.9 The tertiary structure is the further folding of the polypeptide
stabilized by interactions between R groups.
http://cnx.org/resources/36c08f3ac1c144763610fa69fbb9e278/Figure_03_04_08.jpg

28. 7.3 U.10 The quaternary structure exists in proteins with more than one
polypeptide chain.
• Quaternary structure is the linking together of two or more
polypeptides to form a single protein.
• The protein structure below has 4 different polypeptide chains.
http://www.topsan.org/@api/deki/files/6029/=EK5976M_Fig3Comparisons.png

29. 1. Fibrous Proteins
– Insoluble in Water
– Structural (support/strength)
Example
–Collagen (tissue strengthening)
–Keratin (hair/nails)
–Elastin (skin)
Two major types of quaternary Proteins
Each color represents an alpha helix
7.3 U.10 The quaternary structure exists in proteins with more than one
polypeptide chain.

30. 2. Globular Proteins
• Can be soluble in water
• Functional (enzymes and antibodies)
Examples
• Amylase (digestion of starch)
• Insulin (blood sugar regulation)
• Hemoglobin (carry O2)
• Immunoglobulin (antibodies)
7.3 U.10 The quaternary structure exists in proteins with more than one
polypeptide chain.

31. Ribosomes effect in translation
• Ribosome are found in Prokaryotes (70's) and Eukaryotes (80's).
Including P and A sites. START codons and STOP codons begin and
termination translation.
Polyribosome= Polysomes
• Multiple ribosomes on the same mRNA at the same time.
• All ribosome move 5' to 3' in sequence.
• In protein synthesis polyribosomes increase the quantity of
polypeptide synthesized.
7.3 S.1 Identification of polysomes in electron micrographs of
prokaryotes and eukaryotes.

32. 7.3 S.1 Identification of polysomes in electron micrographs of
prokaryotes and eukaryotes.
• In prokaryotes,
several ribosomes
can attach
themselves to the
growing mRNA
chains to form a
polysome while
the mRNA chains
are still attached
to the DNA

33. 7.3 S.1 Identification of polysomes in electron micrographs of
prokaryotes and eukaryotes.
• In eukaryotes, the mRNA
detaches from the DNA
and is then transported
through pores in the
nuclear envelope to the
ribosomes in the
cytoplasm. Once in the
cytosol, eukaryote mRNA
can also form polysomes

34. Conserved sequence: a
homologous sequence of DNA
that is identical across all
members of a species.
Bioinformatics: uses computer
databases to store and analyze
gene & protein sequences from
large amounts of data collected
from sequencing genes of
various organisms
Faster, more powerful computers allow scientist to identify
conserved sequences & genes by looking for patterns and
homologous sequences within organisms’ genome. If a
sequence is homologous across species or individuals of a
species, it usually has a functional role. Eg. It codes for a
protein (a gene).
7.3 S.2 The use of molecular visualization software to analyze the
structure of eukaryotic ribosomes and a tRNA molecule.