lecture 3 biopolymers - hope collegekrieg/chem121_2007/lectures/lecture5... · 2007. 1. 19. ·...
TRANSCRIPT
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Lecture 3Biopolymers• Carbohydrates
• Nucleic Acids
• Proteins
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Functional Group Summary
Alcohol Ether Thiol
Carboxyl Ester Amide
Aldehyde KetonePhosphate
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A carboxylic acid and an amine combine through acondensation reaction to form a…
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Ether
Carboxylicacid
EsterAmide Ketone
H - N - CH3
HAmine
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Condensation Reaction
• For instance, nylon is a polyamide
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Monosaccharides
• 20 natural kinds, mostly in 2 types– Pentoses (5 carbons – ribose)– Hexoses (6 carbons – glucose, fructose)
• Hexoses can have either 5 or 6-member rings• All have an ether O in the ring
– Ether is the starting point for numbering
Fructose(C6H12O6)
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Monosaccharides (part deux)
• Each has several possible isomers– Starch (yummy) contains α-glucose– Cellulose (yucky) contains β-glucose
CH2OH
Note little typo in book in Fig 13-16
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Polysaccharides• Monomers are joined by condensation reaction to make an ether
linkage– The ether O is called the glycosidic oxygen
• Important class of molecules– Storage of carbohydrates (starches, glycogen)– Structural materials (cellulose, chitin)
Cellulose and chitin aremade from β-glucose –they form sheetsinterconnected by eitherH-bonds or amide bonds.
Starch is made from α-glucose and forms longstrands that clump together.
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Importance of Nucleic Acids• All genetic information is stored by DNA• RNA transmits that information from the nucleus out to the cytoplasm,
where proteins are synthesized• RNA is primary component of ribosome• RNA also important in regulation
and a number of other roles• Accuracy is important. Sickle-cell results
from a one AA mutation
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Nucleic acid structures
• G• A• T/U• C
Purines Pyrimidines
Note purine/pyrimidine typo in book figure 13-22
• Individual nucleic acids are connected by sugars and phosphategroups.
– Sugar part of linkage is either ribose or deoxyribose
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What type of chemical reaction joins twoDNA monomers together?
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Nucleic acid structures
• Addition of sugar and phosphate result in the monomerunits for polymeric DNA and RNA.
+
The order of nucleic acidsis called the primary
structure or the sequence.
(ACGT in this example)
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Secondary Structures
• Double-helix structure of DNAelucidated in 1953 by Watson &Crick (data from Wilson &Franklin)
• Earlier Chargaff showed that ratiosof A:T = 1 and C:G = 1
• Hydrogen bonds drive ‘base pairing’– Called Watson-Crick pairs
• H-bonds hold two strands togethervery specifically– allows damage to be sensed and
repaired• Dispersive interactions from the
bases ‘stacking’ on one another isalso very important to stability ofdouble-helix
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RNA forms various structures• Less tendency to ‘pair’• More flexibility• Variety of structures allows variety of function
• Structure and function are intimatelyconnected in all of biology
Transfer RNA –carries aminoacid monomer toribosome
HIV-1initiationcomplex
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Amino Acids• 20 different monomers, differ only in ‘sidechain’• Sidechains differ in polarity (hydrophobicity), charge, size – Chemistry!
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Primary Structure• Condensation rxn makes polyamides (like nylon, kevlar)• Order of AAs is called the primary structure or the (protein) sequence• Small proteins are called peptides
– Many modern drugs are peptides, or peptide-like
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Secondary Structure• The 3-D structure that an amino acid makes with its
neighbors is called the secondary structure• Two most common types
– Helix, or α-helix– Sheet, or β-sheet
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Tertiary Structure
• How pieces of secondary structure pack together• Usually a mix of multiple kinds of secondary structure• Remember: structure ↔ function
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Today• Seminar this afternoon
Monday• Finish CAPA #3• READ Chapt 14