what are proteins? molecular biology...molecular biology the study of proteins and nucleic acids...
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Molecular BiologyThe Study of Proteins and Nucleic Acids
what are proteins?what are the building blocks
of proteins?what type of bond is in
proteins?
Proteins - reviewfunctions include: catalysts for reactions, structure, receptors on membranes, movementstructure:● building block = amino acids● joined by peptide bonds● called polypeptides● 4 levels of structure = primary, secondary,
tertiary, and quaternary
hydrogen bonding between R groups causes folding
what are the parts of an amino acid?Amino Acids● Carbon in the center, w/ a Hydrogen● amino group = NH2● carboxyl group = COOH● "R" group = varies, determines
shape and function
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 - reviewfunctions 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
NucleotidesNitrogenous Base
Sugar - ribose (RNA) or deoxyribose (DNA)
Phosphate
what are the base pairing rules? 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
Nitrogenous Bases2 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)and3' (three prime)
5' ends - phosphates3' ends - sugars
http://youtu.be/wdhL-T6tQcoDNA fantastic! music video
How do we know DNA has the genetic material?
Freidrich Miescher (1868) found nuclear material to be ½ protein and ½ unknown substance1890s - unknown nuclear substance named DNAWalter Sutton (1902) discovered DNA in chromosomes
How do we know DNA has the genetic material?
Frederick Griffith (1928) working with Streptococcus pneumoniae conducted transformation experiments of virulent & nonvirulent bacteria strainsPheobus Levene (1920s) determined 3 parts of a nucleotide
Griffith’s experiment 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
Animationhttp://highered.mcgraw-hill.com/olc/dl/120076/bio21.swf
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
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
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
the famous x-ray photograph of DNA taken by Rosalind Franklincalled “photo 51”
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
you need to know who these people are!
Friedrich Miescher, Hershey & Chase, Frederick Griffith, Rosalind Franklin, Maurice Wilkins, Erwin Chargaff, Watson & Crick
using Chargaff’s (base-pairing) rule
what sequences will be complementary to:
ATTCGCTAACGG
CGGTTACCGAAT
DNA ReplicationReplication = process of copying DNA● occurs at many places along
the DNA molecule simultaneously
● happens in both directions● produces 2 new identical DNA
molecules
DNA Replication
DNA replication is called “semi-conservative” because each new DNA molecule contains half of the original moleculeShown by Meselson-Stahl experiment by Matthew Meselson & Franklin Stahl in 1958http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/bio22.swf::Meselson+and+Stahl+Experiment
semi-conservative DNA replication
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 replicationStep 2: new chains are made by adding/combining complementary nucleotides● DNA polymerase = enzyme adds
nucleotides to new chains
Animations: http://highered.mcgraw-hill.com/olc/dl/120076/bio23.swfhttp://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf
DNA Replication DNA ReplicationStep 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
http://youtu.be/1L8Xb6j7A4wDNA replication music video
what is the location of DNA replication?
what enzymes are involved in the process?
DNA replicationlocation: nucleusenzymes: helicase - unzips DNADNA polymerase - adds/combines new nucleotidesDNA ligase - combines fragments
sites: replication fork - where DNA splitsleading strand - side where DNA is built smoothlylagging strand - side where DNA is built in piecesokazaki fragments - unconnected pieces of DNA on lagging strand
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 RNAinfo goes from DNA --> RNA --> Protein
DNA
RNA
Protein
Transcription
Translation
RNA● stands for RiboNucleic Acid● ribose instead of deoxyribose● uracil (U) instead of thymine (T)
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
TranscriptionTranscription = produces RNA from DNA template● begins at regions called promoters (they
"promote" the transcription)● RNA polymerase = enzyme which synthesizes
RNA
● RNA nucleotides line up along one strand of DNA following the Base-Pairing Rules
● ends at regions called termination signals
Transcription
Animations:http://www.concord.org/~btinker/workbench_web/models/eukTranscription.swfhttp://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf
what is the sequence of molecules in molecular biology?
describe the language of DNA? what is a codon?
what is the location of transcription?
what enzymes are involved in the process?
DNA→transcription→RNA→translation → protein
transcription: location - nucleusenzymes - RNA polymerasesites: promoters - begin processtermination signals - end processtemplate DNA strand - used as template to make RNAinactive DNA strand - not used, RNA is single stranded
TranslationTranslation = making proteins from information in mRNA● occurs on one or more ribosomes ● the 'language' of nucleic acids is 'translated'
into the 'language' of proteins
Translation● 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
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
mRNA
amino acidstRNA
translation
translation Translation● 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
polypeptide new amino acid
translation TranslationAnimations:http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.htmlhttp://www.concord.org/~btinker/workbench_web/models/eukTranslation.swf
protein synthesis music videohttp://youtu.be/JTc18Yh7bSU
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 ERenzymes - none, uses tRNA - brings amino acidsand rRNA - ribosomes to combine amino acidssites: codon - set of 3 nucleotides on mRNA, match up with -anticodon - set of 3 nucleotides on tRNA start codon - begin processstop codon - end processbinding site on ribosome - where mRNA and tRNA line up