unit+1+ +introductory+lecture

8/7/2019 UNIT+1+ +Introductory+Lecture

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UNIT 1: Introduction - Chemical and PhysicalFoundations of Biochemistry

Learning goals : to understand about Roles of small and large biomolecules

Energy transformation in living organisms

Regulation of metabolism and catalysis


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Albert Lehninger (1917-1986)Citric acid cycle occurs in mitochondria

Mechanism of oxidative phosphorylation

Mitochondrial structure and function

Bioenergetics

Author of classic textbooks :

B iochemistry (1970-1983)The Mitochondrion (1964)

B ioenergetics (1965 -1974)


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T he Interface Between Biology and

Chemistry


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Chemistry within the Cell


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Biochemistry : Unique Role of Carbon

Biomolecules are carbon-basedElements H, O, N, P, S are also commonMetal ions (e.g. K +, Na +, Ca ++, Mg++, Zn++, Fe ++) playimportant roles in metabolismTogether, about 30 elements are essential for life


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Biological Molecules T ypically HaveSeveral Functional Groups


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Structure of Biological Molecules isImportant

T he function of molecules strongly depend on three-dimensional structure


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Stereoisomers have DifferentBiological Properties

Cis and trans isomers have also different physical andchemical properties


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Optical Isomers have Different BiologicalProperties

Enantiomers have identical physical properties (except regardto polarized light ) and react identically with achiral reagents.

Diastereomers have distinct chemical and biologicalproperties because bio-molecules are themselves chiral.


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Interactions between Bio-molecules areSpecific

Macromolecules have unique binding pockets

Only certain molecules fit in well and can bind

Binding of chiral bio-molecules is stereospecific


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T he Molecular Logic of Life

We look at the chemistry that is behind :

Accelerating reactions

Organization of metabolism and signaling

Storage and transfer of information


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How to Speed Reactions Up?

Higher temperatures

Stability of macromolecules is limiting

Higher concentration of reactants

Costly as more valuable starting material isneeded

Lower activation barrier by catalysis

Universally used by living organismsChange the reaction by coupling to a fast one

Universally used by living organisms


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Unfavorable and Favorable

ReactionsSynthesis of complex molecules and many other metabolicreactions requires energy (endergonic )

A reaction might be thermodynamically unfavorable (( Gr

> 0)

Creating order requires work and energy Metabolic reaction might have too high energy barrier (( G > 0)

Metabolite is kinetically stable

Breakdown of some metabolites releases significant amount of energy (exergonic )

Such metabolites (ATP, NADH, NADPH) can be synthesizes using the energyfrom sunlight and fuels

Their cellular concentration is far higher than their equilibriumconcentration.


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Catalysis

A catalyst is a compound that increases the rate of achemical reaction

Catalysts lower the activation free energy ( G

Catalysts does not alter ( G

Catalysis offers : Acceleration under mild conditions High specificity Possibility for regulation


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Energy Coupling

Chemical coupling of exergonic and endergonicreactions allows otherwise unfavorable reactions toproceed

Biology often links the hydrolysis of the high-energymolecule AT P directly with the metabolite that needs

activation thus coupling the two reactions.


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AT P: Chemical Currency of Energy


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Metabolic Pathwayproduces energy or valuable materials

Signal Transduction Pathwaytransmits information

Series of Related ReactionsForms a Pathway


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Example of a negative regulation :Product of enzyme 5 inhibits enzyme 1

Pa thw ays Are Contr o lled in Order toRegul a te Level s of M et a b o lite s


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Chapter 1: Summary

T he main learning goals were :To relate structure and function of the cellTo realize that the structure of biomoleculesoften gives them specific functionsTo grasp principles of bioenergetics

unit+1+ +introductory+lecture

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