Transcript Making Proteins - Foothill Technology High School

DNA
Making Proteins
This image
summarizes the
processes of
transcription and
translation.
What are the three
stages in this process
(central dogma) and
where are they in this
picture?
mRNA
rRNA
protein
tRNA
RNA
• RNA (Ribonucleic Acid)
– Contains Ribose as the sugar in its sugarphosphate backbone
• RNA has Uracil rather than Thymine as a
base
– Base pairs: A – U C – G
• 3 types of RNA
– messenger (mRNA)
– transfer (tRNA)
– ribosomal (rRNA)
Two Steps to Protein Synthesis
1. Transcription: mRNA is made from a
strand of DNA
2. Translation: Protein is made by a
ribosome by using mRNA as the set of
“instructions.”
Transcription
in Prokaryotes
• DNA is transcribed into
mRNA
Translation
in Prokaryotes
• mRNA serves as the
instructional material to
make proteins
Transcription
in Eukaryotes
• DNA is transcribed into
pre-mRNA
RNA Processing
in Eukaryotes
• Non-coding regions of
the mRNA, called
introns, are removed
from the pre-mRNA.
Translation
in Eukaryotes
• The mRNA with only
the coding region (the
exons) leaves the
nucleus.
• Translation from
mRNA to protein
occurs in the
cytoplasm.
Steps of DNA Transcription
Making mRNA from DNA
1. Helicase unzips DNA at the gene of interest
2. RNA polymerase matches RNA nucleotide
bases to DNA, using one side as a template.
3. The mRNA strand is created. It now
compliments the original DNA strand (G-C
and A-U).
4. Ligase helps the strand of DNA to close
again.
5. mRNA strand moves out of nucleus to
ribosomes, DNA zips up.
Key Players in Translation
rRNA = RNA that makes up a ribosome
tRNA = RNA that transfers specific amino acids
mRNA = carries the DNA message;
RNA transcribed from DNA
Codon = 3 nucleotides in a row on a strand of
mRNA that code for an amino acid
Anticodon = 3 nucleotides in tRNA that base
pair with the codon
Amino Acids = monomers of proteins
(20 in humans)
Steps to Translation
Making proteins from mRNA
1. Ribosomes attach to the “start” codon of
mRNA (AUG), signaling the beginning of the
protein chain
2. mRNA codons are matched to corresponding
tRNA anticodons and appropriate amino acids
are strung together.
3. Dehydration synthesis occurs between the
amino acids, and they join, making a protein
chain with peptide bonds in between
4. Ribosomes detach when they come across a
“stop” codon (UAA, UAG, UGA). Protein
synthesis is complete.
Why do you
think RNA
uses the
“triplet
code”?
Do the math on
your own or
with a
neighbor.
CODON BINGO
• Fill in the Bingo Card (on page 45) with the
20 different amino acids.
– Use your table on page 44 to help
– Watch out for repeated amino acids!
• Wait for your teacher to begin calling out
DNA letters to begin playing
Translation
Activity
• You and your
classmates need to
discover the
hidden protein in
your bag.
• Follow the
instructions in the
bag to unlock the
mystery protein.
What if a single base is changed?
What if a single base is changed?
What if a single base is changed?
Proteins
•
•
Made up of Carbon, Hydrogen, Oxygen
and Nitrogen (and some Sulfur)
Proteins are responsible for many
reactions
Types of Proteins
I am completely
1. Enzymesunchanged,
Catalysts
that speed up the
I =am
an enzyme.
and
Hi
sweeties,
Dosite.
I
am
the
active
I am
going
tomore
try
rate ofyou
a chemical
reaction
ready
for
some
rememberbindsI am a product, too.
The substrate
convert
you.substrate
sucrose!
– Build up me?
ortobreak
down
to me.
I am a fructose now.
• Fit together with its substrate like a “lock” and a
I am now“key”
a product.
In addition
I am a glucose
now. to what
– Not used
in theI am
reaction
youup
know.
a
– Work in asubstrate.
very specific biological range
– Usually end with “-ase”
Proteins
2. Structural Proteins
– Provides mechanical support to cells and
tissues
3. Transport Proteins
– Transports small ions or molecules
4. Motor Proteins
– Enables structures to move
Proteins
5. Hormones (signaling proteins)
– Carries signals from cell-to-cell
– e.g., insulin
6. Storage
– Stores small molecules or ions
– e.g., iron is stored in the liver in ferritin
7. Other specialized functions
– Defense (immune system antibodies),
– Receptor proteins (in eyes and muscles to
detect stimulus)
Proteins
•
Proteins monomers are called amino acids
– Peptide Bond:
Bond between 2 Amino Acids:
H2O
Proteins
•
•
•
•
A chain of amino acids are called
“polypeptides”
Poly peptides “Many Peptides”
Polypeptides fold and twist to form a
specific shape
Two or more polypeptides form a
complete protein
These shapes
allow proteins to function
Endo-membrane
System
A system of membrane organelles that
are inter-related in their function
How are the organelles of the
endomembrane system interrelated?
Take notes on the following slides
as your teacher narrates what is
happening
What’s up?Do you remember
I have a bit of a
we go too
I Well,
am a before
ribosomal
I am the
complex, because I go
me?
far, we must
subunit…
soonnot
to forget
Nucleus…I’ll give youabout
by several different last
a hint:
Sometimes
become
ame!
ribosome.
what do I I am in chargeI’m
names.
of rough and
do for themaking ribosomes
However,
my first name
sometimes
smooth…
Follow
me as I I’m
travel
to
cell? and the RNAnoused
matter
the
E.R. what, I’mis always Golgi.
to make proteins!
always important to
protein synthesis!
Which does
give me a
complex as
well…
How does this design compare to
what we have already learned
about protein synthesis?
Now let’s look at some more
detailed animations!
http://www.stolaf.edu/people/giannini/
flashanimat/cellstructures/dna.swf
http://www.johnkyrk.com/er.html
How are proteins created by the
“free” ribosomes differ in destination
from the proteins created by the
“attached” ribosomes of the ER?
Attached
Ribosomes:
They proteins
make proteins
Free Ribosomes:
They make
that stay that
withinare
either
the
cytoplasm. The cell uses these proteins itself.
1) secreted out of the cell
2) attached to the plasma membrane
3) stays enclosed in a membrane to function as
another organelle, such as a lysosome.
You will now create a poster of
the endomembrane system to
demonstrate your understanding
of how all the organelles work
together.