Download PROTEIN SYNTHESIS

PROTEIN SYNTHESIS
PROTEIN SYNTHESIS
• Process of using DNA to make protein
• Function of protein in body
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Enzymes
Immunity
Communication between cells
structural
Characteristics (skin color, eye color, etc…)
Structure of DNA
• Double helix
• Nucleotides
– Dexyribose (5 carbon sugar)
– Phosphate
– Nitrogen base (A,T,C,G)
DNA
DNA
BASES
HELPERS
• RNA - ribonucleic acid
– Single strand of nucleotides
– Can act as a messenger between DNA and
ribosomes
Ribosomes - where protein is “constructed”
3 types of RNA
mRNA
tRNA
rRNA
3 Stages of Protein synthesis
• 1. Transcription - “write recipe down”
• 2. Translation - “put recipe together”
• 3. Elongation - “glue” amino acids
together to form protein
SUMMARY
Transcription
• Occurs in nucleus of cell
• Process by which molecule of DNA is
copied into complementary strand of
mRNA
Steps of Transcription
1. DNA unwinds and unzips (helicase)
(only in area of the recipe) creating 2
strands. An active strand and
“dummy”strand
2. Active strand is the one to be used to
make the protein (the template)
3. Special sequence of DNA is
recognized by RNA polymerase as the
“start signal” (promoter)
Steps of transcription cont…
4. RNA polymerase matches up complementary
bases between DNA and RNA (A-U, C-G),
using DNA as a template
5. RNA polymerase moves along the area of the
DNA with the recipe, matching up
complementary bases (elongation phase)
6. when it hits the “stop codon” mRNA drops off
DNA.(termination phase)
7. At this point mRNA has “copied” the recipe
for the protein.
8. DNA winds back up and mRNA gets
modified before leaving the nucleus
TRANSCRIPTION
mRNA modification
• While still in the nucleus, mRNA gets
modified.
• mRNA consists of exons and introns
• An enzyme comes along and splices out the
introns (pieces of DNA) that is not part of the
recipe needed for the protein.
• Exons are then spliced together to create the
“real recipe” for the protein your body needs
• Exons are capped and tailed for protection
and then leave the nucleus via nuclear pores.
EXONS AND INTRONS
WHY COPY DNA????
• DNA is too large to leave the nucleus,
so it needs a messenger to bring
genetic information to the ribosome in
the cytoplasm.
• This messenger is the mRNA
TRANSLATION
• Process of decoding mRNA into protein
• Code being translated from language of
nucleic acids into polypeptide
STEPS OF TRANSLATION
• 1. mRNA attaches onto a ribosome and the
first codon “start” is read by the ribosome.
This signals ribosome to start translating the
recipe (initation phase)
• 2. The ribosome reads each codon of mRNA
and signals tRNA (complementary nitrogen
bases which are carrying a specific amino
acid. (Also called an anticodon)
• 3. Complementary tRNA matches up with
mRNA codon, and brings the amino acid
along with it.
IN THE CYTOPLASM
• 4.
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Translation
cont….
The ribosome moves along the mRNA
reading it and signaling tRNA to bring amino
acids to the ribosome.
5. The amino acids are bonded together, the
previous one with the next one in line.
(elongation)
6. This continues until the ribosome hits the stop
codon. (terminiation)
7. When hits stop codon, mRNa breaks off and
returns to the nucleus (disassembles)
8. All that is left is a string of amino acids in a
specific order. This specific order is what
determines the name and type of protein that
was just made.
TRANSLATION ON
RIBOSOME
TRANSLATION
Translation
ELONGATION
• The string of amino acids is bonded
together (during the process of
translation) to create the protein that
your body needs.
• http://www.wisconline.com/objects/index_tj.asp?objID=
AP1302