4. nbj
These are chromosomes (colored
bodies) located in the nucleus and
mitochondria of cells. Everyone
has 46 chromosomes from their
parents. Inside the chromosomes
are DNA molecules.
25. The start codon signals the
mRNA strand to attach to the
ribosome.
Large subunit
Ribosome
Builds proteins
made up of rRNA
Small
subunit
A
U
Start Codon
mRNA strand
G
U
C
A
A
G
U
A codon is simply a group of 3
nucleotides.
C
G
A
U
G
Stop codontells RNA to
stop
A
26. Amino acid
tRNA comes in with
an anitcodon
complementary to
the corresponding
codon.
tRNA
A
U
G
U
C
A
A
G
U
C
C
A
U
G
A
U
G
A
61. tRNA keeps coming in
and the amino acids
continue to form
peptide bonds. After
the bonds form, tRNA
“falls off.” This
process continues
until the stop codon
is reached.
U
A
A
U
G
U
G
C
C
A
U
A
A
G
U
C
G
A
U
G
A
146. We finally have a chain of amino acids put together through
dehydration synthesis forming a polypeptide chain. This
chain breaks off the ribosome which falls off the mRNA
strand. We now have a protein, however, it has no function
yet in chain form!
147. Finally, we have the final protein
folded up in its tertiary structure!
148. Protein Synthesis Essay
Protein synthesis is the process within a cell when new
proteins are made. The first step in protein synthesis is
transcription. In transcription, a strand of single-stranded
mRNA is copied from the DNA sequence in a gene. In fact,
the word transcribe means to put thought, speech, or data
in print, so just like pieces of information are copied and
passed on, the same happens in protein synthesis. It is
important to know that transcription occurs in the nucleus
of a cell. Located inside the nucleus are strands of DNA
(found in the chromosomes with chromosome meaning
“colored bodies”). To begin, the enzyme, RNA polymerase
149. Protein Synthesis Essay
comes in, binds at the promoter region, and splits the
double helix DNA strand which resembles a twisted ladder,
into single- strands. Then, one of the strands is used as a
template as RNA polymerase adds complementary
nucleotides to the template. This all happens in the coding
region or the main part of the gene that codes for amino
acids. The termination sequence signals the polymerase to
stop. Obviously, RNA polymerase uses RNA instead of DNA,
but there are other differences such as uracil is found in
RNA that replaces the nitrogen base thymine, RNA is singlestranded, and RNA is made of ribose sugar. Once everything
is matched up on the template and complementary strand,
the molecule, mRNA is created,
150. Protein Synthesis Essay
meaning messenger RNA. The single strands of DNA bind
together again and the mRNA strand breaks off the
template strand. The new strand of mRNA moves out of
nucleus, exiting a nuclear pore into the cytoplasm of the
cell.
Next, the second part of protein synthesis is translation.
“Translation is the process of converting the nucleotide
sequence of an mRNA molecule into a language that is
understood by protein-making machinery (ribosomes). This
language is made up of amino acids.” So, this process occurs
in the ribosomes when the start codon signals the mRNA to
attach to the ribosome. A ribosome is the organelle that is
responsible for building proteins made up of rRNA
(ribosomal RNA) and a ribosome also consists of
151. Protein Synthesis Essay
two parts; a large subunit and a small subunit. The
ribosomes read the mRNA sequence and convert it into an
amino acid sequence. The mRNA is read in codons (a set of
three nucleotides) as every codon codes for one amino
acid. It all begins at the start codon composed of the
nucleotide sequence “AUG” called methionine, when tRNA
(transfer RNA) comes in with an amino acid and anticodon.
An anticodon, then, is simply a group of three nucleotides
complementary to the codon on the mRNA strand. The
amino acid forms a peptide bond with the adjacent amino
acid, as the tRNA “falls off.” This process continues as the
amino acids are put together through dehydration synthesis
until the ribosome reaches the stop codon (UGA), signaling
the end when the last tRNA falls off. The end
152. Protein Synthesis Essay
product is a polypeptide chain. In other words, we have a
protein chain as the protein monomer is an amino acid. The
chain breaks off the ribosome and falls off the mRNA
strand. However, this chain has no function until it folds
into the secondary and final tertiary structure. Finally, we
have a globular shaped protein!
