protein synthesis the molecule of life: transcription and translation
TRANSCRIPT
Transcription and Translation
Transcription begins the process of protein synthesis
Translation results in the end protein molecule
Several organelles in the cell are involved
Transcription: Start of Protein Synthesis Where?
Nucleus in Eukaryotes Cytoplasm in Prokaryotes
What? Many cell organelles involved RNA Polymerase plus some minor proteins DNA code becomes encoded in mRNA
Transcription: Start of Protein Synthesis When?
When RNA is needed
Why? RNA’s serve many important functions in
cells RNA encodes protein sequences
How?
Transcription Defined
Transcription: to transfer a code into another code ie. To rewrite one language into another
Transcription
How? mRNA made 5’3’ directionality DNA unzips only at a specific gene
sequence for a specific protein Usually only one strand of DNA is read to
form a complementary copy of the mRNA
Transcription
Uses Base-pairing but U instead of T pairs with A.
RNA nucleotides “float” into place with the aid of RNA polymerase and complementary base pairing occurs
There are nonsense codes at the end of the gene that terminate mRNA synthesis.
mRNA breaks off and moves out of the nucleus into the ribosomes of the cytoplasm
Same idea as with DNA replication Transcription Animation Transcription & translation - fast
Translation
When? When proteins are need, after mRNA is made
Why? Proteins are vital for cells
Enzymes, tissues, hormones, cell structure all require proteins
Translation: Defined
Translation: to interpret a code into meaning.
In biology: The process by which messenger RNA directs the amino acid sequence of a growing polypeptide during protein synthesis.
Proteins: Structure and Function Amino acids connect to form small
chains called peptides, which get larger and form polypeptides.
There are 20 amino acids useful to humans
We consume these in our diet, our body makes a few
Proteins: Structure and Function In anabolism, our body needs to
assemble these amino acids into specific protein structures. A missing amino acid means an entire protein cannot be made—the RNA cannot “fill” the hole left by its absence
A.A. allow the protein molecule to form its necessary structure
Proteins have many structures/shapes
Translation
How? Ribosomal Subunits
Small subunit Large subunit
Codon on mRNA Triplet nucleotide code used Each triplet codes for a specific tRNA
attached to a specific amino acid
A couple definitions
CODON: a triplet of nucleotides on the mRNA Triplet codes for a specific tRNA
complementarity The codon is the genetic code
ANTICODON: A triplet of nucleotides on the bottom of the
tRNA Triplet anticodon complements the mRNA
codon Brings attached to its 3’ end an amino acid
Test for Understanding the code A DNA sequence has the
following bases: T A C - A G A - T T A - G G G - A T T What amino acids does it code for? (You'll need to use the codon chart)
mRNA CODONSAUG UCU AAU CCC UAAMet–ser – asn – pro-stop
AUG usually is “START”UAA is “STOP”
Amino acid sequence is actually SER-ASN-PRO
tRNA each has one specific amino acid and this is how amino acids “know” the sequence of attachment !
Recall tRNA
Anticodon attaches to codon
Amino acid valine is attached to this specific tRNA
Valine will always attach to tRNA with the same anticodon
Amino acid binding site is amino acid specific