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Proteins
Proteins
• involved in EVERYTHING!– structural AND functional
(enzymes = most important)
• tens of thousands of different proteins– each has a specific shape and function
• HUGE polymers– created from just 20 amino acids (monomers)
© 2012 Pearson Education, Inc.
• Structural proteins provide associations between body parts.
• Contractile proteins are found within muscle.• Defensive proteins include antibodies of the
immune system.• Signal proteins are best exemplified by
hormones and other chemical messengers.• Receptor proteins transmit signals into cells.• Transport proteins carry oxygen.• Storage proteins serve as a source of amino
acids for developing embryos.
© 2012 Pearson Education, Inc.
Proteins: commonalities
Proteins: differences
• based on R groups• hydrophobic (non-polar)• hydrophilic (polar)
Proteins: creation
• aa monomers are linked together through:dehydration synthesis
• create a peptide bond• 1 + 1 = dipeptide• 1 + 1 + 1 (etc.) = polypeptide
Proteins: structure
Primary: aa sequence (aa used + order they’re in)
Secondary: hydrogen bond interactions (between N-C-C backbones of aa)
Tertiary: R group interactions(hydrogen bonds + covalent bonds)
Quarternary: (not all proteins) individual subunits put together to make a larger unit
© 2012 Pearson Education, Inc.
http://www.answers.com/topic/alpha-helix and http://www.nature.com/horizon/proteinfolding/background/figs/importance_f3.html
p. 45
http://www.di.uq.edu.au/sparqproteins
http://themedicalbiochemistrypage.org/protein-structure.html
http://www.youtube.com/watch?v=lijQ3a8yUYQ
http://www.pdb.org/pdb/explore/jmol.do?structureId=3LDC&bionumber=1
http://www.wiley.com/legacy/college/boyer/0470003790/animations/protein_folding/protein_folding.htm
Denaturedprotein
Nativeprotein
Enzymes
• biological catalysts: cause rxns to happen faster than they normally would
• rxns would happen anyway-just not at the speed necessary for life
• cause reaction to happen but are not altered by the rxn
• shaped based: specific enzymes cause specific reactions
Enzymes
• substrate + enzyme → product
Enzyme Enzyme–substratecomplex
Product
Enzyme
Activesite
Figure 5.13A_1
Activationenergy barrier
Reactant
Products
Without enzyme
Ener
gy
Figure 5.13A_2
Activationenergy barrierreduced byenzyme
Reactant
Products
With enzyme
Ener
gy
Enzyme
Figure 5.14_s11
Enzyme(sucrase)
Active site
Enzyme availablewith empty activesite
Figure 5.14_s2
2
1
Enzyme(sucrase)
Active site
Enzyme availablewith empty activesite
Substrate(sucrose)
Substrate bindsto enzyme withinduced fit
Figure 5.14_s3
3
2
1
Enzyme(sucrase)
Active site
Enzyme availablewith empty activesite
Substrate(sucrose)
Substrate bindsto enzyme withinduced fit
Substrate isconverted toproducts
H2O
Figure 5.14_s4
4
3
2
1
Products arereleased
Fructose
GlucoseEnzyme(sucrase)
Active site
Enzyme availablewith empty activesite
Substrate(sucrose)
Substrate bindsto enzyme withinduced fit
Substrate isconverted toproducts
H2O
Rate of Reaction
• temperature• pH• cofactors (coenzyme if organic)• competitive inhibitors
– block active site
• noncompetitive inhibitors – Δ shape of enzyme = non-fxnal active site
Figure 5.15A
Substrate
Enzyme
Allosteric site
Active site
Normal binding of substrate
Competitiveinhibitor
Noncompetitiveinhibitor
Enzyme inhibition
Reactionwith enzyme
Maximum rate
Reaction withoutenzyme
http://www.youtube.com/watch?v=PILzvT3spCQ&feature=related
http://www.google.com/imgres?imgurl=http://faculty.une.edu/com/courses/bionut/distbio/obj-512/Chap9-enzymeinhibition.gif&imgrefurl=http://faculty.une.edu/com/courses/bionut/distbio/obj-512/Chap9-enzymeinhibition.html&usg=__o-Vr2YNMsbP9gRLNqt4HqljbiRg=&h=553&w=862&sz=20&hl=en&start=6&zoom=1&tbnid=0B0iggD_l2xkDM:&tbnh=93&tbnw=145&ei=30ecTtL2F6LnsQL2-4CkCA&prev=/search%3Fq%3Dcompetitive%2Benzyme%2Binhibition%26hl%3Den%26gbv%3D2%26tbm%3Disch&itbs=1