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Bellringer-Write down 3
interesting things about DNA that you
didn’t know before. On page 15.
You should have learned at least 3 things.
Protein SynthesisProtein Synthesis
What is protein synthesis?Is protein synthesis important?
What is RNA?
Where is RNA found?Is RNA similar to DNA?
What is translation?
What is Protein Synthesis?
*Protein synthesis is the building
of proteins following the instructions of DNA.
*The instructions of DNA are written by the order of the bases.
Example of instructions on DNA:
A - G - A - T - C - T - A - G
Why is protein synthesis important?
*Proteins make up the structure of an organism AND control all of the organism’s chemical reactions to keep it alive.
Examples of proteins:Walls of arteries, ligaments, hair, nails, muscles , bones and antibodies.
Protein Structure
A protein is made up of a chain of AMINO ACIDS in a particular order, held together by PEPTIDE BONDS.
Example of Protein:*a chain of Amino Acids
Alanine Phenylalanine Glutamine Valine Proline Lysine
NAMES OF AMINO ACIDS
Actual Sequence and names
of AMINO ACIDS
In Blood (Hemoglobin)
Shapes of Proteins
*the shape of a protein depends on its function & its order of amino acids.
Where does protein synthesis occur?
*The DNA never leaves the nucleus.
*RNA copies the DNA in the nucleus.
*RNA carries the instructions from DNA out to the ribosome.
*The protein is built on the ribosome in the cytoplasm.
DNA in the nucleus is safe !!
DNA in the cytoplasm can be
destroyed
What is RNA?
RNA (ribonucleic acid)
*It is the nucleic acid responsible for
three things in protein synthesis:
1 – copying instructions from DNA
2 – carrying the instructions for
making proteins to the ribosome,
3 – putting the protein together on
the ribosome.
What makes up RNA?
Bases in RNASugar in RNA
Ribose
Strands in RNA
“ONE”
3 Types of RNA1. Messenger RNA (mRNA)2. Transfer RNA (tRNA)3. Ribosomal RNA (rRNA)
mRNA tRNA rRNA
Messenger RNA (mRNA)
Function: 1. Goes into the nucleus and makes a copy of DNA using
RNA bases. 2. Takes the copy to the ribosomes.3. Contains the “CODON” (group of 3 bases on mRNA)
Transfer RNA (tRNA)
Function:- carries amino acids to mRNA at the ribosome to (make) the protein.- contains “ANTICODON” (3 bases that match up w/codon on mRNA)
Ribosomal RNA(rRNA)*ribosomal RNA
major structural part of the ribosome where protein synthesis occurs.
Comparison of Comparison of DNA and RNADNA and RNA
*DNA* * RNA*
Strands: 2 1
Sugar: deoxyribose ribose
A, G, C, T A, G, C, UBases: *Thymine *Uracil
(A – T) (A – U)
Steps in Protein Synthesis
Part I – Transcription
Part II – Translation:
Step 1: TranscriptionStep 1: Transcription
Location: in the nucleusPurpose: to copy the DNA code (order of bases) onto mRNA.Events:1.) DNA is unwound and DNA helicase unzips DNA strand.2.) RNA polymerase reads the complementary base and adds the new
nucleotides along the DNA strand.3.) mRNA is made, leaves the nucleus to go to ribosome.
Step 1: TranscriptonStep 1: Transcripton
Location: in the nucleus
Main Event: mRNA comes into
the nucleus and makes
a copy of the order of
thebases on DNA.
RNA polymerase
Function:
Enzyme that recognizes
the complementary base
of RNA to DNA, and glues
them together.
Examples:
Guanine with Cytosine
Adenine with Thymine
*Uracil with Adenine
Step 2: TranslationStep 2: Translation
Location: in the cytoplasm, on the ribosome.Purpose: to convert the instructions of RNA (order of bases) into
amino acids, to make proteins.
Step 2: TranslationStep 2: Translation
Events of translation:1.) The first three bases of mRNA (codon) join the ribosome.
Usually (AUG – considered the start codon).2.) tRNA brings the “amino acid” down to the ribosome. The three
bases on tRNA (anticodon) match the complementary bases on mRNA.
Step 2: Translation … (final Step 2: Translation … (final stage)stage)
Events of translation:3.) Each tRNA has an AMINOACID, that is determined byits anticodon.
Ex: codon (AUG)Amino Acid - methionine
4.) The amino acids arejoined by polypeptide bonds.5.) The resulting chain of amino acids are called aPROTEIN.
Codons & Anticodons
Codon – def: three nucleotides of mRNA.
STOP codons - UAA, UAG, UGA - all three of these codons signal the end of a polypeptide chain
Codons - *C U A - *G G C - *A A C - *U U AAmino Acids Leucine - Glycine - Asparagine - Leucine
ANTICODON - segment of three bases on tRNA that are complementary to the mRNA codon.
Start codon - AUG codons signals the start of a polypeptide chain
TRANSLATION
& tRNA
in pictures
Closeup of translation…(mRNA, codons)
tRNA, amino acids, peptide bonds
Protein Synthesis, summary…
Protein Synthesis, summary…
Animations
• DNA Replication review
• Transcription & Translation
Practice with Amino Acids
• What is the Amino Acid for : – AUG – CCU – UGG – AGU