A QUICK INTRODUCTION Protein Synthesis

Key Terms Gene RNA mRNA tRNA rRNA Transcription Translation Codon Anticodon Ribosome Denature RNA Polymerase

Protein What? Synthesis!!  The combination of parts into a whole Protein Synthesis  The process our cells go through to make proteins

Protein Synthesis Video We will watch this twice Write down things YOU think are important from this video (write at least 5) &feature=related &feature=related

Protein Synthesis There are 2 steps of protein synthesis  Transcription  Translation The central dogma states that information flows in one direction from DNA to RNA to proteins.  DNA  RNA  Protein RNA connects the 2 steps  mRNA carries DNA’s instructions

replication transcription translation

What is a protein? A chain of molecules called amino acids Used in almost every process of our cells (replication, respiration) Provides structure (used to create cell walls, bone and muscle) Examples:  Hemoglobin  Insulin  DNA polymerase  major component of cartilage and hair

DNA contains the information required to make proteins DNA must be copied before proteins can be made Why?  DNA is master blueprint of the cell – needs to be kept safe  Cell needs to make a lot of proteins  Needs to make a lot of copies of DNA mRNA is the copy of DNA used to make proteins

RNA RNA (Ribonucleic Acid) is very similar to DNA but there are a few differences  Different sugar - ribose instead of deoxyribose  Single-stranded  Uses uracil instead of thyamine

Types of RNA There are 3 types of RNA  mRNA - messenger RNA, carries the message or instructions to make a particular protein  rRNA - ribosomal RNA, makes up ribosomes  tRNA - transfer RNA, transport amino acids (the building blocks of protein) to the ribosome

Step 1: Transcription Protein Synthesis starts in the nucleus with transcription. Transcription is very similar to replication. Transcription and replication both involve complex enzymes and complimentary base pairing. The two processes have different end results.

Replication copies all the DNA; transcription copies a gene.  RNA Polymerase complex binds to DNA at the beginning of a specific gene  unzips DNA  Like DNA Polymerase, RNA Polymerase matches base pairs  Remember, instead of using thymine to pair with adenine we use uracil to pair with adenine.

After Transcription Once the gene is completely copied  DNA is zipped back up  mRNA leaves the nucleus  DNA is left unchanged  As many copies of RNA can be made as needed

Step 2: Translation During translation the mRNA is used to create a polypeptide, or protein. After the DNA has been copied mRNA leaves the nucleus and enters the cytoplasm where it binds to a ribosome.

Translation The ribosome “reads” the mRNA strand 3 bases at a time – called a codon  Each codon codes for a specific type of amino acid  One start codon, AUG  Three stop codons UAA, UAG, UGA Regardless of the organism, codons code for the same amino acid.

As the ribosome reads the mRNA codons, tRNA brings(transfers) the correct amino acid to the ribosome An anticodon is a set of three nucleotides that are complementary to an mRNA codon.  An anticodon is located on the tRNA. The amino acid is attached to the growing chain with peptide bonds by the ribosome

Translation: Detailed View For translation to begin, tRNA binds to a start codon and signals the ribosome to assemble.  a complementary tRNA molecule binds to the exposed codon, bringing its amino acid close to the first amino acid  the ribosome helps form a peptide bond between the amino acids  the ribosome pulls the mRNA strand length of one codon  the now empty tRNA molecule exits the ribosome  a complementary tRNA molecule binds to the next exposed codon.  once the stop codon is reached, the ribosome detaches the protein and disassembles

Once the amino acid is added to the protein chain the tRNA detaches and leaves the ribosome to get another amino acid.

Protein Structure Proteins are more than long strings of amino acids. They must be folded in order to function correctly

Proteins can be damaged or “denatured” Denature is a change in shape and function of a protein caused by forces such as temperature or pH changes Can Proteins be Damaged?

Important! Every somatic cell in your body has the exact same DNA!! How come the cells in your body act different if they all contain the same DNA?  Some cells make hair while some digest your lunch. It is all in the genes and proteins they express!