what are proteins? what are the building blocks of proteins? what type of bond is in proteins? Molecular Biology Proteins - review Amino Acids

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1 Molecular Biology The Study of Proteins and Nucleic Acids what are proteins? what are the building blocks of proteins? what type of bond is in proteins? Proteins - review functions include: catalysts for reactions, structure, receptors on membranes, movement structure: building block = amino acids joined by peptide bonds called polypeptides 4 levels of structure = primary, secondary, tertiary, and quaternary what are the parts of an amino acid? hydrogen bonding between R groups causes folding Amino Acids Carbon in the center, w/ a Hydrogen amino group = NH2 carboxyl group = COOH "R" group = varies, determines shape and function

2 what are nucleic acids? what are the building blocks of nucleic acids? what are bases? what do we call the shape of DNA? Nucleic Acids - review Nucleotides Nitrogenous Base functions include: energy currency (ATP), store hereditary information (DNA & RNA) structure: building block = nucleotide nitrogenous bases - A, T, C, G and U sugar-phosphate backbone double helix shape what are the base pairing rules? Phosphate DNA's Double Helix nitrogenous bases of nucleotides pair up in a certain manner C with G A with T these base pairs form the steps of a twisted ladder shape Sugar - ribose (RNA) or deoxyribose (DNA)

3 Nitrogenous Bases 2 kinds: purines and pyrimidines Purines - adenine and guanine Pyrimidines - thymine and cytosine Base-Pairing Rules (Chargaff s Rule) purine always pairs up with pyrimidine adenine with thymine guanine with cytosine bases "pair up" by hydrogen bonding DNA is "antiparallel" ends are called: 5' (five prime) and 3' (three prime) 5' ends phosphates 3' ends - sugars DNA fantastic! music video

4 How do we know DNA has the genetic material? Freidrich Miescher (1868) found nuclear material to be ½ protein and ½ unknown substance 1890s - unknown nuclear substance named DNA Walter Sutton (1902) discovered DNA in chromosomes Griffith s experiment How do we know DNA has the genetic material? Frederick Griffith (1928) working with Streptococcus pneumoniae conducted transformation experiments of virulent & nonvirulent bacteria strains Pheobus Levene (1920s) determined 3 parts of a nucleotide How do we know DNA has the genetic material? Hershey-Chase experiment Alfred Hershey and Martha Chase studied bacteriophages, which are made of only DNA and protein radioactively labeled the DNA and protein see which substance (DNA or protein) moved into infected cells Hershey-Chase experiment Animation http: //highered. mcgrawhill. com/olc/dl/ /bio 21.swf

5 Hershey-Chase Experiment conclusions - proteins did not enter infected cell, DNA did enter infected cell therefore - DNA must contain genetic code to make more viruses Rosalind Franklin and Maurice Wilkins Took X-Ray photographs of DNA discovered DNA must have a helix shape This photograph later inspired the model made by Watson and Crick James Watson and Francis Crick figured out 3 dimensional structure of DNA was a double helix used information discovered by Chargaff, Franklin and Wilkins to figure it out How do we know the structure of DNA? Contributors: Erwin Chargaff (1950s) discovered that every species has different amounts of A, T, C and G discovered that the amount of A always equals amount of T and amount of C always equals amount of G the base pairing rules are aka Chargaff s rule the famous x-ray photograph of DNA taken by Rosalind Franklin called photo 51 you need to know who these people are! Friedrich Miescher, Hershey & Chase, Frederick Griffith, Rosalind Franklin, Maurice Wilkins, Erwin Chargaff, Watson & Crick

6 using Chargaff s (base-pairing) rule what sequences will be complementary to: ATTCGCTAACGG CGGTTACCGAAT DNA Replication DNA Replication Replication = process of copying DNA occurs at many places along the DNA molecule simultaneously happens in both directions produces 2 new identical DNA molecules semi-conservative DNA replication DNA replication is called semi-conservative because each new DNA molecule contains half of the original molecule Shown by Meselson-Stahl experiment by Matthew Meselson & Franklin Stahl in /sites/dl/free/ /120076/bio22.swf::meselson+and+stahl+experiment DNA Replication Step 1: the 2 nucleotide strands are separated by unwinding origin of replication = site where DNA replication begins replication fork = where 2 chains separate helicase = enzyme breaks hydrogen bonds holding the bases together DNA replication Step 2: new chains are made by adding/combining complementary nucleotides DNA polymerase = enzyme adds nucleotides to new chains Animations: com/olc/dl/120076/bio23.swf edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf

7 DNA Replication DNA Replication Step 3: okazaki fragments on the lagging strand are joined together by the enzyme DNA ligase leading strand - replication in the direction the DNA molecule is being unzipped happens smoothly lagging strand - replication in the other direction is fragmented okazaki fragment - fragments on the lagging strand DNA replication results in 2 new identical DNA molecules parent strand - part of original DNA molecule daughter strand - newly formed strands DNA replication music video what is the location of DNA replication? what enzymes are involved in the process? DNA replication location: nucleus enzymes: helicase - unzips DNA DNA polymerase - adds/combines new nucleotides DNA ligase - combines fragments sites: replication fork - where DNA splits leading strand - side where DNA is built smoothly lagging strand - side where DNA is built in pieces okazaki fragments - unconnected pieces of DNA on lagging strand

8 The Language of DNA information in DNA is in the sequence of bases a triplet (set of 3) of nitrogenous bases is called a codon these are like words in the language of DNA The Language of DNA DNA's information is expressed as proteins each codon codes for an amino acid each gene codes for a polypeptide DNA never leaves the nucleus the code to make proteins is sent to the ribosomes using messenger RNA info goes from DNA --> RNA --> Protein RNA DNA Transcription stands for RiboNucleic Acid ribose instead of deoxyribose uracil (U) instead of thymine (T) RNA Protein 3 types of RNA messenger RNA (mrna) = carries genetic info from nucleus to cytosol transfer RNA (trna) = carry amino acids to be built into proteins ribosomal RNA (rrna) = make up ribosomes Transcription Transcription = produces RNA from DNA template begins at regions called promoters (they "promote" the transcription) RNA polymerase = enzyme which synthesizes RNA

9 Transcription RNA nucleotides line up along one strand of DNA following the Base-Pairing Rules ends at regions called termination signals what is the sequence of molecules in molecular biology? describe the language of DNA? what is a codon? what is the location of transcription? Animations: org/~btinker/workbench_web/models/euktrans cription.swf edu/people/giannini/flashanimat/molgenetics/tra nscription.swf DNA transcription RNA translation protein transcription: location - nucleus enzymes - RNA polymerase sites: promoters - begin process termination signals - end process template DNA strand - used as template to make RNA inactive DNA strand - not used, RNA is single stranded what enzymes are involved in the process? = making proteins from information in mrna occurs on one or more ribosomes the 'language' of nucleic acids is 'translated' into the 'language' of proteins mrna slides through ribosomes trna brings amino acids to ribosomes trna contains sequences called anticodons which contain 3 bases complementary to a codon in the mrna anticodon trna

10 translation always begins at a start codon - AUG on mrna each mrna codon pairs with trna anticodon amino acids form peptide bonds together and then detach from the trna amino acids trna mrna translation polypeptide ribosome moves along the mrna from codon to codon new amino acids are brought by trnas and added to the polypeptide the process stops at a stop codon translation new amino acid Animations: edu/biochem/gp2/m_biology/animation/gene/gene _a3.html org/~btinker/workbench_web/models/euktranslati on.swf protein synthesis music video

11 Protein Processing a polypeptide is only the primary shape of a protein the R groups of the amino acids will cause the polypeptide chain to fold and bond with other polypeptides many proteins also need other compounds added for ex. glycoproteins need carbs added this is accomplished in the golgi apparatus what is the location of translation? what molecules are involved in the process? what bonds are formed? DNA transcription RNA translation protein translation: location - ribosomes in cytoplasm or on ER enzymes - none, uses trna - brings amino acids and rrna - ribosomes to combine amino acids sites: codon - set of 3 nucleotides on mrna, match up with anticodon - set of 3 nucleotides on trna start codon - begin process stop codon - end process binding site on ribosome - where mrna and trna line up