Download of the protein - Duplin County Schools

Protein Synthesis
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The Making of Protein
Quick Protein Review
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A chain of amino acids is a protein.
Protein is a macromolecule or polymer.
Proteins an organic molecule with C,H,O,N.
Monomer of protein is amino acid.
There are 20 amino acids, found in food.
Ribosomes make protein.
Proteins make up structural and functional
components of the cell.
Protein structure is determined by the genetic code in
your DNA. The section of DNA that codes for one
protein is called a gene
A gene is a section of
DNA that determines
the sequence of amino
acids in a protein.
Therefore, the gene
determines the shape
and therefore, the
function of the
protein it codes for.
1. Structural: proteins help make up all structures in living things
Actin & Myosin: muscle proteins
Keratin: nails, hair,
horns, feathers
Collagen: bones, teeth, cartilage, tendon,
ligament, blood vessels, skin matrix
2. Functional: other proteins help us to keep our bodies
functioning properly and to digest our food.
Enzymes: lower the
energy of activation to
digest our food and to
assist in cellular
metabolism.
Hemoglobin
The Kingdom of Celltropolis
Once there was a kingdom with a beautiful
palace named Celltropolis!
This kingdom was run by King DNA,
he was a very wise king!
In this kingdom there were Ribosome Villages,
who all had the same problem- they needed
instructions to build complex bridges!
King Deoxyribonucleic Acid
and his palace lovingly
named Nucleus!
1. Can you find
Kingdom Cell,
King DNA,
and palace
Nucleus?
2. What happens
in the nucleus?
Ribosome Villages
all have the same
problem they need
to build bridges for
various purposes.
The instructions
to build these various
Bridges or Proteins
must come from
King DNA.
King DNA has the blueprint instructions for building protein
Messenger guy (mRNA) goes into nucleus and gets instructions
Witchdoctors or translators (tRNA) translate the messenger for ribosome
The amino acids brought by witchdoctors are materials for bridge
The bridges are protein
Part 1 of Story Transcription
Messenger from Ribosome
Village runs to palace to
GET INSTRUCTIONS from
King DNA.
Transcription complete!!!!
mRNA receives message
Step One: Transcription
(Trans = across, scription = to write)
The coded message of a gene on DNA has specific instructions
on how to make each particular protein that our bodies need
The instructions from a gene are copied
from DNA to messenger RNA (mRNA)
in the nucleus
Then, the mRNA moves through the
nuclear pores and into the cytoplasm
where the proteins are made.
DNA
mRNA
A
U
T
A
C
G
G
C
The process of making mRNA is called TRANSCRIPTION
Enzymes involved!
Step 1: Helicase unwinds the DNA (starting at the promoter).
Step 2: Complementary RNA base pairs attach to form the mRNA
strand
Step 3: RNA polymerase forms the RNA sugar-phosphate backbone
and checks for mistakes
Step 4: The RNA detaches & leaves the nucleus, & the DNA winds
back up
Part 2 - Back at
Village Ribosome
There is a PROBLEM!
No one in the village
Can read the message from
King DNA. It is in some
strange language!
Witchdoctors (tRNA) BRING
Materials for Bridges
called Amino Acids.
Rest of the STORY:
Witchdoctors (tRNA) come
down from hill country and
Translate the message so it
Can be read by ribosome rRNA.
*Proteins (Bridges) made!!!!
Bridge (Protein) Complete!
Step Two: Translation
 The mRNA code is made up of groups of three nucleotide
bases known as codons. Each codon codes for a specific
amino acid. Use the CODON Chart provided.
Example AGC = Serine
Example UGC = Cysteine
CAU?
AUG?
CUU?
GGC?
UGA?
AAA?
mRNA
Codon chart
1. Find the amino
acid for UUG.
2. Which do you
like better the
round or
square
codon chart?
Another example of a Codon Chart
Why a Triplet Code?
It takes 3 nucleotides on the mRNA to code for 1 amino acid
Why? We must code for 20 different amino acids and there
are only 4 letters (nucleotides) in the DNA alphabet.
With a single nucleotide, there are only 4 possible codes (41).
For two nucleotides, there are only 16 possible codes (42).
However, for three nucleotides there are 64 possible codes
(43), and that is enough to code for the 20 amino acids.
Step 2: Translation
•The written code (codons) on mRNA is ‘translated’ into a
specific amino acid sequence by ribosomes in the
cytoplasm.
•This is carried out with
the help of relatively
small transfer RNA
(tRNA) molecules.
A tRNA molecule is a small piece of RNA that has a
specific amino acid attached to it.
The tRNA also has a
special sequence of 3
nucleotide bases known
as an anticodon.
There is at least one type of tRNA for each of the 20 amino
acids.
As the correct amino acids are brought to the ribosome by the
tRNAs, they are joined together by Peptide Bonds to form the
protein that the original DNA coded for.
Please note that there is more than one codon for each
amino acid:
mRNA codons:
U C U
G C C
tRNA anti-codons:
A G A
C G G
SERINE
ALANINE
Why do you think that is?
4. TERMINATION: The last codon on any mRNA molecule
is called the ‘TERMINATOR’ codon, which is a message to
STOP translation.
This codon will be either UAA, UAG, or UGA. None of
these have a matching tRNA anticodon, so when no more
tRNA’s attach, the ribosome, protein, and mRNA detach from
each other.
A BAD NIGHT AT THE THEATRE
Question: What if something goes wrong during translation?
Answer: MUTATION
•
A change in the
nucleotide
sequence of DNA
•
When the bases (‘letters’)
change, the wrong amino
acids are used to make
the protein.
•
The protein will NOT be
able to do its job.
There are 2 types of MUTATION:
1. Chromosomal mutations: a mutation of all or part of a
chromosome.
This usually involves MANY GENES, and therefore, MANY
PROTEINS.
Example: Down’s syndrome.
2. Gene mutations: a mutation that occurs within a gene at
some point along a chromosome. This mutation is only a
change of 1 or a few ‘letters’ (nitrogenous bases).
It usually only affects ONE GENE, and therefore, ONE
PROTEIN.
Example: Sickle cell anemia.