Protein Synthesis

Protein Synthesis • The Making of Protein

Quick Protein Review • A chain of amino acids is a protein. • Protein is a macromolecule or polymer. • Proteins an organic molecule with C,H,O,N. • Monomer of protein is amino acid. • There are 20 amino acids, found in food. • Ribosomes make protein. • Proteins make up structural and functional components of the cell.

Protein structure is determined by the genetic code in your DNA. The section of DNA that codes for one protein is called a gene A gene is a section of DNA that determines the sequence of amino acids in a protein. Therefore, the gene determines the shape and therefore, thefunction of the protein it codes for.

Actin & Myosin: muscle proteins Keratin: nails, hair, horns, feathers Collagen: bones, teeth, cartilage, tendon, ligament, blood vessels, skin matrix Proteins Have 2 Main Functions • Structural: proteins help make up all structures in living things

Enzymes: lower the energy of activation to digest our food and to assist in cellular metabolism. Hemoglobin 2. Functional:other proteins help us to keep our bodies functioning properly and to digest our food.

The Kingdom of Celltropolis Once there was a kingdom with a beautiful palace named Celltropolis! This kingdom was run by King DNA, he was a very wise king! In this kingdom there were Ribosome Villages, who all had the same problem- they needed instructions to build complex bridges!

King Deoxyribonucleic Acid and his palace lovingly named Nucleus!

1. Can you find Kingdom Cell, King DNA, and palace Nucleus? 2. What happens in the nucleus?

Ribosome Villages all have the same problem they need to build bridges for various purposes. The instructions to build these various Bridges or Proteins must come from King DNA.

Roles of Characters King DNA has the blueprint instructions for building protein Messenger guy (mRNA) goes into nucleus and gets instructions Witchdoctors or translators (tRNA) translate the messenger for ribosome The amino acids brought by witchdoctors are materials for bridge The bridges are protein

Part 1 of Story Transcription Messenger from Ribosome Village runs to palace to GET INSTRUCTIONS from King DNA.

Transcription complete!!!!

mRNA receives message

mRNA A T C G DNA The instructions from a gene are copied from DNA to messenger RNA (mRNA) in the nucleus Then, the mRNA moves through the nuclear pores and into the cytoplasm where the proteins are made. Step One: Transcription(Trans = across, scription = to write) The coded message of a gene on DNA has specific instructions on how to make each particular protein that our bodies need U A G C

The process of making mRNA is called TRANSCRIPTION

Enzymes involved! Step 1: Helicase unwinds the DNA (starting at the promoter). Step 2: Complementary RNA base pairs attach to form the mRNA strand Step 3: RNA polymerase forms the RNA sugar-phosphate backbone and checks for mistakes Step 4: The RNA detaches & leaves the nucleus, & the DNA winds back up

Part 2 - Back at Village Ribosome There is a PROBLEM! No one in the village Can read the message from King DNA. It is in some strange language!

Witchdoctors (tRNA) BRING Materials for Bridges called Amino Acids. Rest of the STORY: Witchdoctors (tRNA) come down from hill country and Translate the message so it Can be read by ribosome rRNA. *Proteins (Bridges) made!!!!

Bridge (Protein) Complete!

Step Two: Translation ·The mRNA code is made up of groups of three nucleotide bases known as codons. Each codon codes for a specific amino acid. Use the CODON Chart provided. Example AGC = Serine Example UGC = Cysteine AUG? CAU? CUU? AAA? UGA? GGC?

mRNA Codon chart

1. Find the amino acid for UUG. • Which do you like better the • round or • square • codon chart? Another example of a Codon Chart

Why a Triplet Code? It takes 3 nucleotides on the mRNA to code for 1 amino acid Why? We must code for 20 different amino acids and there are only 4 letters (nucleotides) in the DNA alphabet. With a single nucleotide, there are only 4 possible codes (41). For two nucleotides, there are only 16 possible codes (42). However, for three nucleotides there are 64 possible codes (43), and that is enough to code for the 20 amino acids.

Step 2: Translation • The written code (codons) on mRNA is ‘translated’ into a specific amino acid sequence by ribosomes in the cytoplasm. • This is carried out with the help of relatively small transfer RNA (tRNA) molecules.

The tRNA also has a special sequence of 3 nucleotide bases known as an anticodon. There is at least one type of tRNA for each of the 20 amino acids. A tRNA molecule is a small piece of RNA that has a specific amino acid attached to it.

As the correct amino acids are brought to the ribosome by the tRNAs, they are joined together by Peptide Bonds to form the protein that the original DNA coded for.

Please note that there is more than one codon for each amino acid: mRNA codons: U C U G C C tRNA anti-codons: C G G A G A SERINE ALANINE Why do you think that is?

4. TERMINATION: The last codon on any mRNA molecule is called the ‘TERMINATOR’ codon, which is a message to STOP translation. This codon will be either UAA, UAG, or UGA. None of these have a matching tRNA anticodon, so when no more tRNA’s attach, the ribosome, protein, and mRNA detach from each other.

A BAD NIGHT AT THE THEATRE Question: What if something goes wrong during translation? Answer: MUTATION • A change in the nucleotide sequence of DNA • When the bases (‘letters’) change, the wrong amino acids are used to make the protein. • The protein will NOT be able to do its job.

There are 2 types of MUTATION: • Chromosomal mutations: a mutation of all or part of a chromosome. • This usually involves MANY GENES, and therefore, MANY PROTEINS. • Example: Down’s syndrome. • Gene mutations: a mutation that occurs within a gene at some point along a chromosome. This mutation is only a change of 1 or a few ‘letters’ (nitrogenous bases). • It usually only affects ONE GENE, and therefore, ONE PROTEIN. • Example: Sickle cell anemia.

Protein Synthesis