Protein Synthesis 9 Biology
Terminology DNA Protein synthesis mRNA tRNA rRNA RNA polymerase Helicase Codon Anti-codon Ribosome E.R. Polypeptide Amino acid Triplet
Proteins are synthesized: To make Communication molecules Signals on cell membrane To make Antibodies Fight pathogens To make Transport molecules Protein channels in cell membranes To make Enzymes Catalyze reactions
How do the proteins get synthesized? Protein “recipe” is on DNA Order of the nitrogenous bases dictates the protein made DNA has the information, but cannot leave the nucleus. mRNA is used to copy the protein recipe, take it out of the nucleus, and have it translated by ribosomes and tRNA
RNA-Ribonucleic Acid RNA is: 3 Types: Single stranded Has base pairing BUT Has no Thymine Uses Uracil instead So… A pairs with U G pairs with C 3 Types: mRNA- messenger RNA tRNA- transfer RNA rRNA- ribosomal RNA Ribosomes are made of rRNA, and are synthesized in the nucleolus
Protein Synthesis Step 1: Transcription DNA molecule uses helicase to unzip in the area where the protein recipe is mRNA copies the DNA strand using RNA polymerase and with A,U,G,C in the proper complementary order
Protein Synthesis Step 2: Translation mRNA leaves the nucleus and heads for a ribosome Ribosome puts mRNA strand( codon) in contact with tRNA (anti-codon) tRNA encodes for amino acids using “triplets” of code 3 bases= 1 amino acid
Protein Synthesis Step 3: Amino acids form a polypeptide chain protein Protein assumes its folding pattern It will be used in cell or exported for use outside the cell Protein translated in cytoplasm used in cell Protein translated in E.R. exported
How Code on DNA Becomes Protein Order of nitrogenous bases encodes for proteins- Change base sequence, change the protein made Protein expression is visible: Eye color Height Physical features Protein expression is also invisible: Enzyme action Antibody generation Cell signalling Order of bases on DNAcopied by mRNAtranslated to protein by tRNA and ribosomes