PROTEIN SYNTHESIS Protein Synthesis Assembly of proteins Occurs

PROTEIN SYNTHESIS

Protein Synthesis Assembly of proteins Occurs on ribosome 3 Steps DNA code of gene segment must be copied in the nucleus of the cell Code must be carried from the nucleus into the cytoplasm and to the ribosome Protein must be assembled from the code and released from the ribosome

RNA Ribonucleic Acid Molecule used to translate the code from DNA into protein Single stranded Sugar – ribose Nitrogenous Bases A, G, C, U Thymine replaced by Uracil A-U G-C

Types of RNA Messenger RNA Ribosomal RNA Transfer RNA

Messenger RNA m. RNA Manufactured during 1 st step of protein synthesis

Transcription Region of DNA double helix unwinds and separates Separated segment is a gene Serves as a template for the m. RNA

RNA Polymerase m. RNA strand assembled from individual RNA nucleotides present in nucleus Enzyme picks up unattached nucleotide bases and matches them to their complementary bases on the DNA template strand Continues until entire gene segment has been paired Complete m. RNA formed

Transcription RNA polymerase RNA nucleotide Direction of transcription Template strand of DNA Newly made RNA

RNA polymerase DNA of gene Promoter DNA Initiation Terminator DNA Elongation Termination Growing RNA Completed RNA polymerase

• m. RNA is not complete yet • Noncoding segments called introns are spliced out • Exons – EXported from nucleus • Introns – stay IN nucleus • A cap (5’) and a tail (3’)are added to the ends • Cap – help m. RNA bind to a ribosome Tail – keep protein-building message in tact as long as the cell needs Exon Intron Exon DNA Cap RNA transcript with cap and tail Transcription Addition of cap and tail Introns removed Tail Exons spliced together m. RNA Coding sequence NUCLEUS CYTOPLASM

Ribosomal RNA r. RNA m. RNA separates from DNA template and leaves nucleus m. RNA moves into cytoplasm and settles on a ribosome Ribosome contains another kind of RNA Translation takes place on ribosome

Translation Step in protein synthesis where m. RNA is decoded (translated) and corresponding polypeptide is formed Polypeptide made up of amino acids

m. RNA Code m. RNA is a chain of nucleotides AUGACAGAUUAG Read 3 nucleotides at a time Codon Each codon corresponds to a specific amino acid

How Translation Works m. RNA bound to surface of ribosome at first nucleotide segment Start Codon Cytoplasm contains amino acids and another kind of RNA

Transfer RNA t. RNA Contains a three-part nucleotide segment Anticodon • • Complements the m. RNA codon Corresponds to one of the 20 amino acids Binds the amino acid Travels to ribosome surface

Forming the Polypeptide • • Anticodon pairs with complementary m. RNA codon Amino acid bound to t. RNA is added to growing polypeptide chain Ribosome moves m. RNA chain along until stop codon is reached Stop Codon 3 nucleotide sequence Tells ribosome translation is complete Ribosome releases polypeptide chain Fully functioning protein

Translating the genetic code Transcribed strand DNA Transcription RNA Start codon Polypeptide Translation Stop codon

Proteins Enzymes – help carry out reactions within the cell Hormones – chemical messengers that regulate body functions Provide structure Energy source Transport other molecules Part of our immune system