Download PROTEIN SYNTHESIS Proteins made on free ribosomes will be

PROTEIN SYNTHESIS
Proteins are made by
cellular organelles
called ribosomes.
Ribosomes can be
attached to the
endoplasmic reticulum
or freely floating in the
cytosol.
Animal Cell with Organelles shown
Proteins made on free ribosomes will be used
within the cell.
Proteins made on ribosomes attached to
endoplasmic reticulum will be exported out of
the cell.
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THREE TYPES OF RNA
1) mRNA: messenger RNA
2) tRNA: transfer RNA, transfers
amino acids to the ribsome to
build proteins.
3) rRNA: ribosomal RNA, makes up
ribosomes
Transfer RNA (tRNA)
Recall that DNA is
transcribed by mRNA
in the nucleus.
Transcription (in the nucleus)
The mRNA leaves the
nucleus and goes to
the ribosome with the
protein instructions.
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TRANSLATION
A codon is a
group of three
mRNA
nucleotides.
AUG= start codon
Each tRNA
molecule has an
anticodon, which
also has three
nucleotides.
Translation (in the cytosol)
Each tRNA molecule has a specific amino acid
at one end and an anticodon at the other.
The nucleotides in the tRNA anticodon pair up
with the nucleotides in the mRNA transcript
using the base pair rules we learned earlier.
THE GENETIC CODE
The genetic code specifies a correlation
between an mRNA nucleotide sequence and an
amino acid sequence (protein).
mRNA codons bond
with complementary
tRNA anticodons,
which carry amino
acids.
The Genetic Code
UAA, UAG, UGA = Stop codons
In this way, the
amino acid sequence
of a protein is
specified.
SUMMARY OF PROTEIN SYNTHESIS
1) mRNA makes a copy of DNA in nucleus.
2) mRNA leaves the nucleus and goes to a
ribosome in the cytosol.
3) The ribosome (made of rRNA) is the site of
protein synthesis.
4) The mRNA codons bond with complementary
tRNA anticodons.
5) Each tRNA with a given anticodon always
carries the same amino acid.
6) So the sequence of mRNA codons specifies
the sequence of tRNA molecules carrying a
certain amino acid.
7) The amino acids are bonded together with a
peptide bond.