BMMB120 Medical Biology

Report
Group 10
Title : Translation
Lecturer : Mr J . Musona
28 February 2025

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 Researchers :

Natalie Nontobeko Mpofu

PMBCHB24227276

Patricia Mandizvidza
BMS24228070

Deangeles Ndozvo
PMBChB24227979

Sean-Dean Mkombo
PMBChB24227440

Pretty Tafadzwa Chinyama

PMBChB24227572

Karrel Chirongwe
BSN24230179

Yolanda Tafadzwa Matura

PMBChB24227923

Panashe V Chikurukuta
PMBChB24227774

Liyabona Cezula
PMBChB23123116

Roselyn T Musekiwa
PMBCHB24227687

Joseph Masiyanise
PMBCHB24227204

Roxane Garwe
PMBCHB24227598

Annie Ngoma
PMBCHB24226749

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 Translation is a vital segment of Medical Biology , particularly in the study of
Genetics. From the steps taken during this process , the involvement of key
molecules such as tRNA , mRNA , e.t.c. , translation takes genetic information
and converts it into functional ,essential macromolecules called polypeptides
(proteins). Translation is a 4-step process involving , Initiation , Elongation,
Termination and Post-Translational Modi ications ,and all these ensure that
genetic integrity is maintained and proteins are produced as required.

Translation is the process by which the genetic information encoded in

messenger(mRNA) is used to synthesize proteins.It occurs in the ribosomes
and involves the coordinated interaction of mRNA (messenger RNA), tRNA
(transfer RNA) and rRNA (ribosomal RNA).The sequence of nucleotides on
mRNA is read in groups of three known as codons. Transfer RNA molecules,
carry a speci ic amino acid and recognize codons on the mRNA through their
complementary anticodons.Translation plays a crucial role in protein
synthesis as it allows cells to convert genetic information into functional
proteins.Proteins perform a wide range of functions including catalyzing
metabolic reactions, replicating DNA, responding to stimuli and maintaining
cellular structure. The signi icance of proteins makes the study of translation
crucial in biology.

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Research Findings
Whilst conducting our research we discovered that translation has 5 key
players and 4 stages that result in protein production from genetic
information encoded in mRNA. In the following paragraphs ,we will further
explore what role each of these molecules have and what each stage of
translation entails,

Transfer RNA (tRNA)

tRNA in simple words ,is the molecule that brings amino acids from the
amino acid pool to the ribosome where translation is occurring. It does this
when the enzyme , aminoacyl-tRNA synthetase , catalyses the linking of an
amino acid to a tRNA molecule.

Messenger RNA (mRNA)

This type of RNA is synthesized during transcription , and it contains
encoded genetic material copied from DNA. mRNA is synthesized to allow for
ribosomes in the cytoplasm to receive genetic information from DNA in the
nucleus without potentially damaging DNA or jeopardizing the genetic
integrity of a cell.

Ribosomes
Commonly known as “the site of protein synthesis” , these molecules are
where tRNA and mRNA interact to form a polypeptide chain. Ribosomes are
composed primarily of ribosomal RNA (rRNA) and protein. They are made of
two parts , the large subunit , which is where tRNA binds and the small
subunit, where mRNA binds. Ribosomes have 3 attachment sites on the large
subunit ,the P site (Peptidyl-tRNA site) which holds the tRNA currently
attached to the growing polypeptide chain, A site (Aminoacyl-tRNA site)
binds the incoming tRNA carrying a new amino acid to be added to the chain
and E site (Exit site), where the deacylated tRNA (tRNA without an amino

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 acid) is released from the ribosome after transferring its amino acid. When
multiple ribosomes attach to one mRNA strand at once , these ribosomes are
referred to as polyribosomes and they allow for very fast translation of
multiple copies of the protein.

Chaperone Proteins
These are involved in the last stage of translation, post-translational
modi ication.They assist with the proper folding of newly synthesized
polypeptide chains and later in this report we will explore the importance of
a proteins folding to its overall structure.

The stages of Translation proceed as follows,

Initiation
tRNA attached to an amino acid , mRNA carrying the genetic information to
be translated and ribosomes form the initiation complex , the molecular
setup needed to start making a new proteins.The formation of this complex
and subsequently the initiation of protein synthesis requires initiation factors,
molecules that ensure tRNA ,mRNA and ribosome subunits ind each other in
an orderly manner. Additionally , translation-initiation requires energy , this
energy comes in the form of guanosine triphosphate (GTP) which is similar to
adenosine triphosphate (ATP).Here's how translation initiation unfolds inside
cells:

1. A transfer RNA (tRNA) molecule carrying methionine, the usual irst

amino acid, docks onto the small ribosomal subunit.
2. This complex then attaches to the messenger RNA (mRNA) at its 5' end,
recognizing the distinctive 5' GTP cap added during nuclear processing.

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3. The complex then moves along the mRNA in the 3' direction until it
reaches the start codon.
4. At this point, the large ribosomal subunit joins the complex, fuelled by
the energy released from GTP hydrolysis, and translation elongation
begins."

Initiation is also regulated by molecules called Initiation factors. Initiation

factors (IFs) play a crucial role in the translation-initiation process. Here are
some of their key functions:

⁃ Proper Ribosome Assembly

⁃ Recruitment of mRNA and tRNA
⁃ Start Codon Recognition
⁃ Regulation of Translation E iciency
⁃ Prevention of Incorrect Translation Initiation

Elongation
The second stage of translation is Elongation , and this process , typically
referred to as the Elongation Cycle proceeds as follows :

1. Codon Recognition: The ribosome reads the next mRNA codon and
matches it with the complementary tRNA anticodon.
2. Peptide Bond Formation: Peptidyl transferase catalyses the formation of
a peptide bond between the growing polypeptide chain and the new
amino acid.
3. Translocation: The ribosome moves one codon forward along the mRNA,
shifting the tRNA from the A site to the P site, and ejecting the empty
tRNA from the E site.

Elongation ,like Initiation is regulated by Elongation Factors and they’re role

includes ;

⁃ EF-Tu (Prokaryotes) / eEF1A (Eukaryotes): Ensures the correct tRNA binds

to the ribosome.
⁃ EF-G (Prokaryotes) / eEF2 (Eukaryotes): Facilitates ribosomal
translocation to the next codon.
⁃ EF-G (Prokaryotes) / eEF2 (Eukaryotes): Facilitates ribosomal
translocation to the next codon.

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 Termination
The genetic code consists of start and stop codons , start codons such as
AUG (methionine) , initiate translation , stop codons such as UAG , bring
translation to a stop. Translation termination is the inal stage of protein
synthesis where the synthesis of the polypeptide chain stops.This happens
when the stop codons UAA or UAG or UGA reaches the A site of the ribosome
but special proteins called release factors recognize the stop codons and
facilitate the release of the completed polypeptide chain from the
ribosome.The release factor triggers a termination reaction, where a water
molecule is added instead of an amino acid.
This reaction liberates the completed polypeptide chain, and subsequently,
the translation machinery disassembles.

Post-Translational Modi ication

After translation, newly synthesized proteins undergo post-translational
modi ications. These include:
⁃ Phosphorylation - Phosphorylation involves the addition of a phosphate
group to speci ic amino acid, such as serine, threonine, or tyrosine. This
modi ication can activate or inhibit enzyme activity, alter protein-protein
interactions, or regulate protein stability.
⁃ Glycosylation - Glycosylation involves the attachment of carbohydrate
molecules (glycans) to speci ic amino acid, This modi ication can
in luence protein folding, stability, and cell-cell interactions.
⁃ Protein Folding - Protein folding refers to the process by which a
polypeptide chain assumes its native three-dimensional structure. A
process crucial for protein function and stability. This is sometimes
assisted by chaperone proteins, molecules that are a functionally related
group of proteins assisting protein folding in the cell under physiological
and stress conditions
⁃ Building subunits together into a protein with quaternary structure
⁃ Cleaving apart a protein to activate it

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 Eukaryotes and prokaryotes have di erences in structure and function ,these
allow us to compare translation in these respective cells by assessing the
di erences and similarities,

Di erences in translation between eukaryotes and prokaryotes :

In prokaryotic cells, translation occurs in the cytoplasm while in

eukaryotic cells, it occurs in the cytoplasm and in the endoplasmic
reticulum
Prokaryotic cells use a Shine-Dalgarno sequence to initiate translation,
while in eukaryotic cells use Kozak sequence
Prokaryotic ribosomes are smaller (70s) than eukaryotic ribosomes
Eukaryotic cells perform more extensive post-transcriptional modi cation
while prokaryotes do not.

Similarities in translation between eukaryotes and prokaryotes :

Both prokaryotic and eukaryotic cells use ribosomes for translation

Both types of cells use mRNA as the template for translation
Both types of cells use the same 20 amino acids to build proteins

Conclusion
In conclusion, this report has provided an in-depth examination of the
complex process of translation, highlighting the crucial roles of ive key
players - transfer RNA (tRNA), messenger RNA (mRNA), ribosomes,
chaperone proteins, and initiation factors - and the four stages of translation:
initiation, elongation, termination, and post-translational modi ication. Our
analysis has demonstrated the intricate mechanisms underlying protein
synthesis, from the initiation complex formation to the release of the
completed polypeptide chain. Furthermore, we have explored the regulatory
functions of initiation and elongation factors, emphasizing their importance
in ensuring accurate and e icient protein production. In addition we delved
into the comparison of translation in prokaryotes and eukaryotes.Ultimately,
this report underscores the signi icance of understanding translation and its
regulation, highlighting the implications for cellular function, protein biology,
and potential therapeutic applications.

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Citations & References : "Protein Synthesis and Translational Control" by Nahum Sonenberg and
Alan G. Hinnebusch (2009)
"The Mechanism of Eukaryotic Translation Initiation" by Katsura Asano, et al. (2017) - An article
discussing the current understanding of eukaryotic translation initiation mechanisms. (Cell, 169(1),
25-36)
"The Role of Ribosomes in Translational Control" by Maria E. Torres, et al. (2020) - An article
highlighting the importance of ribosomes in regulating protein synthesis. (Trends in Biochemical
Sciences, 45(10), 853-865)