Download amino acids

Proteins are made by decoding the
Information in DNA
Proteins are not built directly from DNA
A molecule called RNA – ribonucleic
acid is used to decode the instructions
in DNA,
RNA Structure
Like DNA, RNA is a nucleic acid.
RNA is a nucleic acid made up of repeating
nucleotides
RNA differs from DNA
in three different ways.
The sugar in RNA is ribose
RNA is single- stranded
RNA contains the base uracil instead of
thymine.
Like thymine, uracil can form bonds with
adenine
Transcription
The instructions for making a protein are
transferred from a gene (DNA) to RNA
Transcription = DNA → RNA
Segment of DNA unwinds
DNA unzips
RNA is produced one nucleotide at a time
by matching base pairs with the nucleotides
in DNA.
After the synthesis is complete, the RNA
separates from the DNA and the DNA
recoils into its helix.
The RNA strand leaves the nucleus and
goes into cytoplasm
In what part of the cell does transcription
take place?
RNA makes proteins.
Where are proteins made in the cell?
Forms of RNA
Messenger RNA - mRNA
mRNA carries the information to
the cytoplasm where the ribosomes
can make it into protein.
–
"Blueprint" for protein synthesis that is transcribed from one strand of the DNA (gene) and which is translated at the
ribosome into a polypeptide sequence
.
Ribosomes take RNA coded information
and "translate" that information into chains
of amino acids called pollypeptides
A protein is made up of one or more
polypeptide chains.
Ribosomal rRNA
• a structural component of the ribosome.
tRNA
molecule that converts nucleic acid sequence
to protein sequence
tRNA - transfer RNA
• It acts as an adaptor to carry the amino acid
elements of a protein to the appropriate place as
coded for by the mRNA.
Small, single-stranded RNA molecules that bind to amino acids and deliver them to the proper codon on messenger RNA.
Messenger RNA (mRNA) is the blueprint
for construction of a protein.
Ribosomal RNA (rRNA) is the construction
site where the protein is made.
Transfer RNA (tRNA) is the truck
delivering the proper amino acid to the site
at the right time.
Translation
The ribosome reads the mRNA sequence
and translates it (or decodes it) into an
amino acid sequence in a polypeptide.
Polypeptides are chains of amino acids.
Proteins are made up of one or more
polypeptide molecules.
So….the building block of proteins are
___________________.
There are 20 essential amino acids that
make up proteins.
The instructions in DNA specify the order
in which the amino acids are put together.
RNA – contains 4 different nucleotides.
(Language – 4 letters)
How can a code with only 4 letters carry
instructions for 20 amino acids?
# of letters
# of words
1
4
2
16
3
64
The genetic code could signify 64 different
words
The group of 3 nucleotides in mRNA that
specifies an amino acid is known as a
codon.
Think of codons as the words of the genetic
message.
Example:
The following sequence of nucleotides in
mRNA
• AAACACGGU
Would be read as 3 codons
AAA- CAC-GGU
And each codon represents a different _____.
First
Second
Third
U
C
A
G
UUU
Phenylalanine
UCU
Serine
UAU
Tyrosine
UGU
Cysteine
U
UUC
Phenylalanine
UCC
Serine
UAC
Tyrosine
UGC
Cysteine
C
UUA
Leucine
UCA
Serine
UAA
STOP
UGA
STOP
A
UUG
Leucine
UCG
Serine
UAG
STOP
UGG
Tryptophan
G
CUU
Leucine
CCU
Proline
CAU
Histidine
CGU
Arginine
U
CUC
Leucine
CCC
Proline
CAC
Histidine
CGC
Arginine
C
CUA
Leucine
CCA
Proline
CAA
Glutamine
CGA
Arginine
A
CUG
Leucine
CCG
Proline
CAG
Glutamine
CGG
Arginine
G
AUU
Isoleucine
ACU
Threonine
AAU
Asparagine
AGU
Serine
U
AUC
Isoleucine
ACC
Threonine
AAC
Asparagine
AGC
Serine
C
AUA
Isoleucine>
ACA
Threonine
AAA
Lysine
AGA
Arginine
A
AUG
Methionine
ACG
Threonine
AAG
Lysine
AGG
Arginine
G
GUU
Valine
GCU
Alanine
GAU
Aspartic acid
GGU
Glycine
U
GUC
Valine
Valine
Alanine
GAC
Aspartic acid
GGC
Glycine
C
GUA
Valine
GCA
Alanine
GAA
Glutamic acid
GGA
Glycine
A
GUG
Valine
GCG
Alanine
GAG
Glutamic acid
GGG
Glycine
G
U
C
A
G
Page figure
Shows all 64 possible codons of the genetic
code.
Notice: More than one codon can specify
the same amino acid.
How do tRNAs recognize to which codon to bring an
amino acid?
The tRNA has an anticodon that is complementary to
the codon on the mRNA. Each tRNA only binds the
appropriate amino acid for its anticodon
amino acids are carried by the molecules of
tRNA.
The ribosomes “read” the codons in mRNA
allowing tRNA molecules to bring the
proper amino acid. (the anti-codon on tRNA
bonds to the proper codon on mRNA)