Protein Synthesis Overview

Protein Synthesis Overview

• Protein synthesis is a two-part process: transcription and translation.
• The goal is to create a protein from a DNA template.
• Transcription occurs in the nucleus, and translation happens in the cytoplasm at ribosomes.
• If given a DNA strand, these processes will create the correct protein.
• DNA and RNA are contrasted.

Transcription

• Transcription is the creation of mRNA from a DNA template.
• This process occurs inside the nucleus.
• DNA "unzips," and RNA polymerase breaks hydrogen bonds between bases.
• Free-floating RNA nucleotides attach to the DNA bases on one side of the DNA molecule.
• Covalent bonds form between sugars and phosphates to create an mRNA strand.
• After creation of the mRNA molecule, the DNA strands "zip" back up and release the mRNA.
• RNA polymerases are enzymes that guide transcription by reading the DNA code.

RNA vs. DNA

• DNA contains thymine, RNA contains uracil.
• DNA is double-stranded, RNA is single-stranded.
• DNA contains deoxyribose, RNA contains ribose.
• One type of DNA, and three kinds of RNA (mRNA, tRNA, rRNA)

Translation

• Translation uses mRNA to make proteins.
• Translation occurs at the ribosomes.
• Anticodons on tRNA molecules are specific to certain amino acids.
• The start codon (AUG) signals the beginning of translation; producing methionine.
• Stop codons (UAA, UAG, UGA) signal the end of translation.
• Amino acids are brought to the ribosome by tRNA, and the tRNA's anticodons bind to the mRNA codons.
• Amino acids are bonded together by peptide bonds to form a polypeptide chain, a protein.

Important Processes

• mRNA takes the code from DNA for the ribosomes.
• tRNA brings amino acids to ribosomes from the cytoplasm.
• Information is transferred from DNA to RNA to proteins—the central dogma of molecular biology.