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)

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• 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