IB Biology HL topic 7.3 Translation Presentation for the new syllabus first exams 2016. Images from the Biology Course Companion have been removed because I do not have permission to reuse them.

1. 7.3 Translation
Essential Idea: Information
transferred from DNA to
mRNA is translated into an
amino acid sequence.
By Darren Aherne Image from
http://www.nobelprize.org/educational/medicine/dna/b/translation/
pics/trans_bd.gif

2. 7.3 Statement Guidance
7.3 U1 Initiation of translation involves assembly of
the components that carry out the process.
Examples of start codons are not
required. Names of the tRNA binding
sites are expected as well as their
roles.
7.3 U2 Synthesis of the polypeptide involves a
repeated cycle of events.
7.3 U3 Disassembly of the components follows
termination of translation.
Examples of stop codons are not
required.
7.3 U4 Free ribosomes synthesize proteins for use
primarily within the cell.
7.3 U5 Bound ribosomes synthesize proteins
primarily for secretion or for use in
lysosomes.
7.3 U6 Translation can occur immediately after
transcription in prokaryotes due to the
absence of a nuclear membrane.

3. 7.3 Statement Guidance
7.3 U7 The sequence and number of amino acids in the
polypeptide is the primary structure.
7.3 U8 The secondary structure is the formation of
alpha helices and beta pleated sheets stabilized
by hydrogen bonding.
7.3 U9 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
U10
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.
7.3 A1 Application: tRNA-activating enzymes illustrate
enzyme–substrate specificity
and the role of phosphorylation.
7.3 S1 Skill: Identification of polysomes in electron
micrographs of prokaryotes and eukaryotes.
7.3 S2 Skill: The use of molecular visualization software
to analyse the structure of eukaryotic ribosomes
and a tRNA molecule.

4. 7.3 S2 The use of molecular visualization software to analyse the
structure of eukaryotic ribosomes and a tRNA molecule.
Ribosome Structure:
• Proteins + ribosomal RNA
(rRNA)
• Large subunit & small subunit
• 3 binding sites for tRNA
(peptidyl- P site, aminoacyl- A
site, exit- E site)
• 2 tRNAs can bind to the
surface of the ribosome at a
time, 1 mRNA can bind to
surface of small subunit
From Biology Course Companion, Allott, A, Oxford University
Press, 2014, p. 363
http://www.rcsb.org/pdb/explore/jmol.do
?structureId=1GIY&bionumber=1
http://www.rcsb.org/pdb/explore/jmol.do?s
tructureId=1JGO&bionumber=1
Click the links to
view the ribosome
images
Image from textbook removed

5. 7.3 S2 The use of molecular visualization software to analyse the
structure of eukaryotic ribosomes and a tRNA molecule.
tRNA Structure:
• Double stranded sections by
complementary base pairing
• Anticodon of 3 bases in a loop
of 7 bases
• 2 other loops
• Amino acid binding site with
CCA sequence of unpaired
bases
From Biology Course Companion, Allott, A, Oxford University
Press, 2014, p. 363
http://www.rcsb.org/pdb/education_discuss
ion/educational_resources/tRNA_jmol.jsp
Click the link to
view the tRNA
images
Image from textbook removed

6. 7.3 A1 Application: tRNA-activating enzymes illustrate enzyme–
substrate specificity and the role of phosphorylation.
• Every tRNA has a specific
enzyme that attaches a
specific amino acid, using ATP
An introduction
https://www.youtube.com/watc
h?v=KThCr1XdUGw
http://highered.mheducation.com/sites/98340923
39/student_view0/chapter15/aminoacyl_trna_hetase.html
Image from textbook removed
From Biology Course Companion, Allott, A, Oxford University
Press, 2014, p. 364

7. 7.3 A1 Application: tRNA-activating enzymes illustrate enzyme–
substrate specificity and the role of phosphorylation.
http://www.phschool.com/science/biology_place/biocoach/translation/addani.html

8. 7.3 U1 Initiation of translation involves assembly of
the components that carry out the process.
Initiation- assembly of
components of translation
• mRNA binds to small
subunit of the ribosome
• Initiator tRNA carrying
methionine amino acid
with anticodon
complementary to AUG
binds to start codon
• Large subunit of ribosome
binds to small subunit
From Purves, Sadava, Orians, & Heller, Life: The Science of Biology,
7th Ed., W.H. Freeman, 2003, p. 244

9. 7.3 U1 Initiation of translation involves assembly of
the components that carry out the process.
Initiation- assembly of
components of translation
• Initiator tRNA is in P-site
• tRNA complementary to
codon at A-site binds to
ribosome
• Peptide bond is formed
between the amino acids
at P and A sites through a
condensation reaction.
From Purves, Sadava, Orians, & Heller, Life: The Science of Biology,
7th Ed., W.H. Freeman, 2003, p. 245

10. 7.3 U2 Synthesis of the polypeptide
involves a repeated cycle of events.
Elongation- a series of
repeated steps
• Ribosome moves 3 bases
along the mRNA
• tRNA at P-site moves to
E-site, allowing it to
disengage
• tRNA complementary to
the codon at A-site
enters
• Process continues many
times
From Purves, Sadava, Orians, & Heller, Life: The Science of Biology,
7th Ed., W.H. Freeman, 2003, p. 245

11. 7.3 U3 Disassembly of the components
follows termination of translation.
Termination- a stop codon
ends translation
• When a stop codon is
reached the polypeptide
is released
• Translation moves in a 5’ –
> 3’ direction
From Purves, Sadava, Orians, & Heller, Life: The Science of Biology,
7th Ed., W.H. Freeman, 2003, p. 246

12. 7.3 U3 Disassembly of the components
follows termination of translation.
Termination- a stop codon
ends translation
• Ribosome breaks apart
following translation
• mRNA may be translated
many times to make many
copies of its polypeptide
From Purves, Sadava, Orians, & Heller, Life: The Science of Biology,
7th Ed., W.H. Freeman, 2003, p. 246

13. Watch these animations about the process of translation. Can you narrate?
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

14. Explain the process of translation leading to polypeptide
formation. (8 marks)

15. Explain the process of translation leading to polypeptide
formation. (8 marks)
a. genetic code consists of codons of base triplets;
b. mRNA is complementary to the DNA strand;
c. mRNA carries information (transcribed) from the DNA gene;
d. translation occurs in a ribosome;
e. mRNA attaches to the (small subunit of the) ribosome;
f. has specific codons;
g. each (codon) codes for one amino acid;
h. tRNA matches its anticodons with the codons of mRNA;
i. by hydrogen bonds between complementary bases;
j. each tRNA carries a specific/OWTTE amino acid;
k. the amino acids are attached to each other by condensation
reactions/peptide bonds;
l. the process is repeated;
m. forming polypeptides;

16. 7.3 U4 Free ribosomes synthesize proteins
for use primarily within the cell.
Location of protein Synthesis: Cell functions & protein synthesis
are compartmentalized (by organelles)
• Proteins that will be used by the cell in the cytoplasm,
mitochondria, and chloroplasts are synthesized on free
ribosomes in the cytoplasm.
http://iws.collin.edu/
biopage/faculty/mcc
ulloch/1406/outlines
/chapter%207/rough
er2.jpg

17. 7.3 U5 Bound ribosomes synthesize proteins
primarily for secretion or for use in lysosomes.
Location of protein
Synthesis:
• Proteins that will be
used in the ER, golgi
apparatus, lysosomes,
plasma membrane, or
to be excreted are
synthesized on
ribosomes bound to the
rER.
• Signal receptor proteins
stop translation until
the ribosome is bound
to the rER.
Image from textbook removed
From Biology Course Companion, Allott, A, Oxford University
Press, 2014, p. 366

18. 7.3 U5 Translation can occur immediately after transcription in
prokaryotes due to the absence of a nuclear membrane.
Transcription & translation are coupled in prokaryotes.
http://www.phschool.com/science/biology_place/biocoach/t
ranscription/tctlpreu.html

19. 7.3 S1 Skill: Identification of polysomes in electron micrographs of
prokaryotes and eukaryotes.
• Polysomes appear as beads
on a string in electron
micrographs.
• “Beads” represent
ribosomes attached to a
single mRNA molecule
• Poly = many, some =
ribosome
http://www.nature.com/scitable/content/27459/
williams_polysome_mid_1.jpg
http://www.nobelprize.org/educational/medicine/dna/a
/translation/pics_em/polysome.gif
Image from textbook removed
From Biology Course Companion, Allott, A, Oxford University
Press, 2014, p. 368

20. 7.3 NOS Developments in scientific research follow improvements in
computing—the use of computers has enabled scientists to make
advances in bioinformatics applications such as locating genes within
genomes and identifying conserved sequences.
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).

21. From i-biology.net

22. 7.3 U7 The sequence and number of amino acids
in the polypeptide is the primary structure.
http://www.stolaf.edu/people/giannini/fl
ashanimat/proteins/protein%20structure
.swf
From i-biology.net

23. From i-biology.net

24. 7.3 U8 The secondary structure is the formation of alpha helices and
beta pleated sheets stabilized by hydrogen bonding.
From i-biology.net

25. 7.3 U9 The tertiary structure is the further folding of the polypeptide
stabilized by interactions between R groups.
http://www.wiley.com/college/boyer/0470003790/ani
mations/protein_folding/protein_folding.htm
From i-biology.net

26. 7.3 U10 The quaternary structure exists in proteins
with more than one polypeptide chain.
Quaternary Structure
• Complex- made of 2 or more
polypeptides folded together
• Includes non-polypeptide
parts, such as the heme group
in hemoglobin, found in
erythrocytes (red blood cells)
• Denature: When a protein is
exposed to changes in pH or
high temperatures, it can
permanently lose its shape
and biological activity (shape
of active site changes
From: http://www.nano.sfedu.ru/research_24.html
Can you identify the
different subunits?
From
http://www.bio.davidson.edu/Courses/Molbio/MolStudents/spring2010/Hua/Hemoglobin.html

27. From i-biology.net

28. From i-biology.net

29. From i-biology.net

30. Thanks to these fine folks,
and any others that I may
have forgotten!