A closer look at transcription and translation Protein Synthesis A closer look at transcription and translation

The many functions of proteins: 1. Structural component - present in skin, hair, muscles 2. Chemical messengers/receivers - hormones 3. Defense against disease - antibodies 4. Enzymes – lactase I’m Team Protein!

What does a protein look like? Proteins are long chains of amino acids.

Secondary and Tertiary Structure The long chains of amino acids (known as polypeptides) coil up to create a functional (working) protein. The protein will not work unless it is coiled up.

There are 20 different amino acids that make up proteins Amino Acids are the building blocks of protein. Thus when you eat protein it gets digested down into individual amino acids and short chains of amino acids that are then absorbed into the bloodstream. These amino acids effect the building and repairing of tissues, as well as producing chemicals that allow our nervous system to function properly. Ther are Essential and Non-Essential Amino Acids. We will worry about the essential ones. HistidineIsoleucineLeucineLysineMethioninePhenylalanineTryptophanValineThese amino acids cannot be made in the body. Your body must get them from complete protein food sources, or combinations of vegetables. Eating these essential amino is very important towards your athletes diet. The essential branched chain amino acids (BCAA’s) are very important towards an athletes diet, because they are metabolized in the muscle, unlike the non-essential ones which are metabolized in the liver. That is because these amino acids are used to build new proteins, rather than being burned as fuel to produce energy.

Structure of the Amino Acids Central carbon surrounded by: Amino group (NH2) Carboxylic acid (COOH) Hydrogen R – functional group Most amino acids look exactly the same except for the _____ group or ________________ group. There are 20 different functional groups that give each amino acid different properties. These are the same on every amino acid R Amino Acids are the building blocks of protein. Thus when you eat protein it gets digested down into individual amino acids and short chains of amino acids that are then absorbed into the bloodstream. These amino acids effect the building and repairing of tissues, as well as producing chemicals that allow our nervous system to function properly. Ther are Essential and Non-Essential Amino Acids. We will worry about the essential ones. HistidineIsoleucineLeucineLysineMethioninePhenylalanineTryptophanValineThese amino acids cannot be made in the body. Your body must get them from complete protein food sources, or combinations of vegetables. Eating these essential amino is very important towards your athletes diet. The essential branched chain amino acids (BCAA’s) are very important towards an athletes diet, because they are metabolized in the muscle, unlike the non-essential ones which are metabolized in the liver. That is because these amino acids are used to build new proteins, rather than being burned as fuel to produce energy. FUNCTIONAL

How does a polypeptide form? aa = amino acid aa + aa + aa + aa aa – aa – aa – aa + Single amino acids polypeptide Connected by a peptide bond

Where do you think that we get the information to make specific proteins? DNA DNA is the blueprint that tells your cell what protein to make. This molecule can be found within the nucleus of the cell. Where are proteins made? On Ribosomes found in the cytoplasm of the cell or attached to the rough endoplasmic reticulum. If the DNA instructions are inside the nucleus and the protein makers are outside of the nucleus them the cell must use an intermediate to get the protein message out!

DNA vs. RNA Video DNA RNA Double Stranded Single Stranded Deoxyribonucleic acid Ribonucleic acid Deoxyribose Sugar Nucleotides -sugar -phosphate -nitrogen base Ribose Sugar Nitrogen Bases -Adenine -Thymine -Cytosine -Guanine Nitrogen Bases -Adenine -Uracil -Cytosine -Guanine Double strands held together by hydrogen bonds A=U C G A=T C G Shorter than DNA Longer than RNA

There are 3 types of RNA Each play an essential role in protein synthesis messenger RNA (mRNA) ribosonmal RNA (rRNA) transfer RNA (tRNA)

What is a gene? A segment of DNA that codes for a specific protein.

Why Transcription? To transcribe means to “rewrite” Transcription is rewriting the DNA language into RNA language!

The beginning of Protein Synthesis DNA A T C G T A G C Transcription : Step 1 Occurs in the nucleus RNA polymerase (an enzyme) binds to the DNA & unzips the DNA RNA polymerase

Protein Synthesis Transcription : Step 2 G U A G C T A G C Transcription : Step 2 RNA polymerase adds free RNA nucleotides using the DNA template Follows the complementary base paring rules: A = U C = G Transcription uses only a specific region of the DNA known as a gene. As RNA polymerase moves past DNA rewinds

Protein Synthesis Transcription : Step 3 G U A G C T A G C Transcription : Step 3 RNA polymerase reaches a specific sequence of nucleotides that marks the end of the gene (“stop” signal) RNA polymerase releases the DNA & newly formed mRNA. mRNA leaves the nucleus.

RNA and Protein Synthesis messenger RNA(mRNA) single stranded Carries the instructions from a gene (DNA) to make a protein Moves from the nucleus to the cytoplasm. Each group of three bases is known as a codon.

RNA and Protein Synthesis ribosomal RNA(rRNA) is part of the structure of ribosomes Ribosomes are made from RNA & other proteins Ribosomes read the mRNA and help assemble the amino acids to make a protein.

RNA and Protein Synthesis transfer RNA(tRNA) transfers the amino acids to the ribosome to make a protein Assembles the amino acids in the correct order based on the codon-anticodon matching.

Transcription This is a molecule of messenger RNA. It was made in the nucleus by transcription from a DNA molecule. codon A U G G G C U U A A A G C A G U G C A C G U U mRNA molecule

Transcription Step1: The mRNA attaches to a Ribosome. Translation will not start until the ribosome reads a “start” codon (usually AUG) ribosome A U G G G C U U A A A G C A G U G C A C G U U

Transcription Amino acid tRNA molecule Step 2: U A C tRNA molecule Step 2: A transfer RNA molecule arrives at the ribosome. It brings an amino acid to the first three bases (codon) on the mRNA. anticodon The three unpaired bases (anticodon) on the tRNA link up with the codon on the mRNA. A U G G G C U U A A A G C A G U G C A C G U U

U A C C C G Transcription Step 3: Another tRNA molecule comes into place, bringing a second amino acid. Its anticodon links up with the second codon on the mRNA. A U G G G C U U A A A G C A G U G C A C G U U

Transcription A peptide bond forms between the two amino acids. U A C C C G Peptide bond A peptide bond forms between the two amino acids. A U G G G C U U A A A G C A G U G C A C G U U

U A C Transcription C C G The first tRNA molecule releases its amino acid and moves off into the cytoplasm. A U G G G C U U A A A G C A G U G C A C G U U

Transcription C C G Step 4: The ribosome moves along the mRNA to the next codon. A U G G G C U U A A A G C A G U G C A C G U U

Transcription C C G A A U Another tRNA molecule brings the next amino acid into place. A U G G G C U U A A A G C A G U G C A C G U U

Transcription C C G A A U A peptide bond joins the second and third amino acids to form a polypeptide chain. A U G G G C U U A A A G C A G U G C A C G U U

Transcription How does it know which amino acid to bring? ala leu arg pro thr A C G met G U C The process continues. The polypeptide chain gets longer. This continues until a termination (stop) codon is reached. The polypeptide is then complete. It is released from the ribosome. A U G G G C U U A A A G C A G U G C A C G U U

Protein Synthesis: How proteins are made Transcription