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DNA, RNA, & Proteins
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Proteins Proteins are large biomolecules made up of amino acids
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Perform many functions in cells such as:
Structural (ex: keratin, collagen) Storage (ex: albumin in eggs) Transport (ex: hemoglobin) Hormonal (ex: insulin) Receptor on cells’ surfaces Defensive (ex: antibodies) Contractile (ex: actin & myosin in muscles) Enzymes which speed up chem. reactions (ex: lactase)
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1° structure: Amino acids form a chain
2° structure: chain becomes pleated or twisted 3° structure: folds into 3D shape 4° structure: more than one amino acid chain
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How to Make Proteins (a.k.a.: Protein Synthesis)
Assembled at ribosome Remains in the nucleus Nucleus ribosome
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DNA vs. RNA RNA: Thymine (T) switched to Uracil (U) Single stranded
Sugar is a ribose
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Three Kinds of RNA… mRNA (messenger RNA) – carries code for protein synthesis to ribosome rRNA (ribosomal RNA) – combines with protein to form ribosome tRNA (transfer RNA) – carries amino acid to ribosome
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Two Steps of Protein Synthesis:
1) Transcription (DNA -> mRNA) 2) Translation (mRNA -> protein)
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Part 1: Transcription DNA is copied into a small strand of mRNA that CAN leave the nucleus
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Part 2: Translation mRNA brings code to ribosome Ribosome reads three mRNA bases at a time, and puts the appropriate amino acid in place These three base “sets” are called codons
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As the ribosome reads the mRNA codons, tRNA (transfer RNA) brings the amino acids.
Each tRNA has an anticodon that base pairs with the codons on one end and a corresponding amino acid on the other end. The amino acids are held together by peptide bonds forming a polypeptide (protein). tRNA continues to bring amino acids until a STOP codon is read. When translation stops, the polypeptide is released.
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20 possible amino acids used to make proteins
Can you determine the corresponding amino acids to the RNA codon? CAC:_________________ GUA:_________________ GCU:_________________ AGG:_________________ 20 possible amino acids used to make proteins 64 possible combinations of codons This leads to duplicates So, mistakes can made without preventing the protein from working!
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Let’s practice building a small protein!
DNA Triplet TAC AGA TGT GAA GTG CGG CCT ATT mRNA Codon Amino acid
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Whoops! A random mutation occurred!
DNA Triplet TAC AGA GT GAA GTG CGG CCT ATT mRNA Codon Amino acid
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