Protein Synthesis The Molecule of Life: Transcription and Translation

Transcription begins the process of protein synthesis Translation results in the end protein molecule Several organelles in the cell are involved

Cell Organelles Involved in Protein Synthesis (186)

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

Where are we?

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

Transcription: Layout 5’ end RNA 3’end RNA

mRNA Enters Cytoplasm

Translation What? mRNA  Protein molecule Where? Cytoplasm Ribosomes are main organelles

Translation When? When proteins are need, after mRNA is made Why? Proteins are vital for cells Enzymes, tissues, hormones, cell structure all require proteins

The Genetic Code

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

Peptide Bond Formation: Dehydration Synthesis

From Amino Acid to Protein Structure

The Big Question? How do amino acids assemble themselves correctly ?

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

Translation How? mRNA, tRNA, & rRNA are all used

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

The Genetic Code

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)codon chart mRNA CODONS AUG UCU AAU CCC UAA Met–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

Summary Translation DNA Rap

Why is this important? Genetic Engineering Gene Splicing Mutations Cloning Castle Analogy