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Intro to MetabolismCampbell Chapter 8

http://www.gifs.nethttp://ag.ansc.purdue.edu/sheep/ansc442/Semprojs/2003/spiderlamb/eatsheep.gif

• Metabolism is the ____ of an organism’s chemical reactions

• Metabolism is an _____________ of life that arises from interactions between molecules within the cell http://www.encognitive.com/images/metabolic-pathways.png

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A metabolic pathway begins with a specific molecule and ends with a ___________

• Each step is catalyzed by a specific enzyme

BIOCHEMICAL PATHWAYVIDEO

ENZYMES THAT WORK TOGETHER IN A PATHWAY CAN BE

Soluble with free floating intermediates

Covalently bound incomplex

Attached toa membranein sequenceBiochemistry Lehninger

Concentrated in specific location

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_____________ PATHWAY (___________)________ of energy by the breakdown of complex molecules to simpler compoundsEX: _________ enzymes break down food

____________ PATHWAY (____________)________ energy to build complicated molecules from simpler onesEX: linking amino acids to form ________

http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/nanoscience/sci_media/images/chemical_reactions_involve_making_new_combinations/53823-2-eng-NZ/chemical_reactions_involve_making_new_combinations_full_size_landscape.jpg

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/I/IntermediaryMetabolism.html

Krebs Cycle connects the catabolic and anabolic pathways

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Forms of Energy• ENERGY = capacity to cause __________

• Energy exists in various forms (some of which can perform work)

• Energy can be ___________ from one form to another

_______________–energy associated with motion– ________ (thermal energy) is kinetic

energy associated with random movement of __________________

_______________ = energy that matter possesses because of its location or structure

– ___________ energy is potential energy available for release in a chemical reaction

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On the platform, the diver hasmore potential energy.

Diving convertspotential energy to kinetic energy.

Climbing up converts kinetic energy of muscle movement to potential energy.

In the water, the diver hasless potential energy.

_____________________= the study of energy transformations

• __________ system (EX: liquid in a thermos)= isolated from its surroundings

• _________ systemenergy + matter can be transferred between

the system and its surroundings

• Organisms are _____ systems

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The First Law of Thermodynamics

= energy of the universe is __________

– Energy can be transferred and transformed

– Energy ________ be created or destroyed

• The first law is also called the principle of ____________________________

http://www.pxleyes.com/photoshop-picture/4a3b747566555/remote-control.htmlhttp://www.suncowboy.com/solar101.php

The Second Law of ThermodynamicsDuring every energy transfer or transformation• _________ (________) of the universe

INCREASES

• some energy is unusable, often lost as heat

http://hyperphysics.phy-astr.gsu.edu/hbase/therm/entrop.html

http://www.janebluestein.com/articles/whatswrong.html

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Chemical energy

Heat

CO2

First law of thermodynamics Second law of thermodynamics

H2O

ORGANISMS are energy TRANSFORMERS!

Spontaneous processes occur without energy input; they can happen quickly or slowly

For a process to occur without energy input, it must ________________ of the universe

Free-Energy Change (____) can help tell which reactions will happen

ΔG = change in free energy ΔH = change in total energy (enthalpy) or change ΔS = entropy T = temperature

ΔG = ΔH - TΔS

• Only processes with a _________________

_____________

• Spontaneous processes can be harnessed to perform work

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Exergonic and Endergonic Reactions in Metabolism• ________ reactions

(- ΔG)

• _________ energy

• are _____________

___________ reactions (+ ΔG)

• _______ energy fromtheir surroundings

• are ____________

Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions

• A cell does three main kinds of work:

– Mechanical

– Transport

– Chemical

• In the cell, the energy from the exergonic reaction of ATP hydrolysis can be used to drive an ____________________

• Overall, the coupled reactions are __________

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Phosphate groups

Ribose

Adenine

ATP (adenosine triphosphate) is the cell’s renewable and reusable energy shuttle

ATP provides energy for cellular functions

Energy to charge ATP comes from ________________

LE 8-9

Adenosine triphosphate (ATP)

Energy

P P P

PPP i

Adenosine diphosphate (ADP)Inorganic phosphate

H2O

+ +

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P

i

ADP

Energy for cellular workprovided by the loss ofphosphate from ATP

Energy from catabolism(used to charge upADP into ATP

ATP

+

Endergonic reaction: DG is __________, reaction is __________________

Exergonic reaction: DG is ___________, reaction is _______________

G = +3.4 kcal/mol

G = –7.3 kcal/mol

G = –3.9 kcal/mol

NH2

NH3Glu Glu

Glutamicacid

_______________________:Overall DG is negative;Together, reactions are spontaneous

Ammonia Glutamine

ATP H2O ADP P i

+

+ +

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LE 8-11

NH2

Glu

P i

P i

P i

P i

Glu NH3

P

P

P

ATPADP

Motor proteinMechanical work: ATP phosphorylates motor proteins

Protein moved

Membraneprotein

Solute

Transport work: ATP phosphorylates transport proteins

Solute transported

Chemical work: ATP phosphorylates key reactants

Reactants: Glutamic acidand ammonia

Product (glutamine)made

+ +

+

Every chemical reaction between molecules involves bond breaking and bond forming

______________________ = amount of energy required to get chemical reaction started

Activation energy is often supplied in the form of heat from the surroundings

http://www.chuckwagondiner.com/art/matches.jpghttp://plato.acadiau.ca/COURSES/comm/g5/Fire_Animation.gif

IT’S LIKE PUSHING A SNOWBALL UP A HILL . . . Once you get it up there,it can roll down by itself

Free energy animation

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LE 8-14

Transition state

C D

A B

EA

Products

C D

A B

G < O

Progress of the reaction

Reactants

C D

A B

Free

ene

rgy

The Activation Energy Barrier

_____________ = a chemical agent that speeds up a reaction without being consumed by the reaction

_____________ = biological catalystsMost enzymes are PROTEINS

Exception = ribozymes (RNA) Ch 17 & 26

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Course ofreactionwithoutenzyme

EAwithout enzyme

G is unaffectedby enzyme

Progress of the reaction

Free

ene

rgy

EA withenzymeis lower

Course ofreactionwith enzyme

Reactants

Products

ENZYMES work by _____________ ACTIVATION ENERGY;

ENZYMES LOWER ACTIVATION ENERGY BY– Orienting substrates correctly

– Straining substrate bonds

– Providing a favorable microenvironment

Enzymes change ACTIVATION ENERGY but _____ energy of

REACTANTS or PRODUCTS

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ENZYMES• Most are _________• ______ activation energy• __________• ________ determines function• ___________• ___________ by reaction

Image from: http://www.hillstrath.on.ca/moffatt/bio3a/digestive/enzanim.htm

• The REACTANT that an enzyme acts on = _______________

• Enzyme + substrate =_________________________

• Region on the enzyme where the substrate binds = ________________

• Substrate held in active site by _________ interactions (ie. hydrogen and ionic bonds)

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TWO MODELS PROPOSED• LOCK & KEY

Active site on enzymefits substrate exactly

• INDUCED FITBinding of substrate causes changein active site so it fits substratemore closely

http://www.grand-illusions.com/images/articles/toyshop/trick_lock/mainimage.jpghttp://commons.wikimedia.org/wiki/File:Induced_fit_diagram.png

– General environmental factors, such as temperature, pH, salt concentration, etc.

– Chemicals that specifically influence the enzyme

http://www.desktopfotos.de/Downloads/melt_cd.jpg http://www.nealbrownstudio.com/adm/photo/163_nb_fried_egg.jpg

See a movieChoose narrated

Enzyme Activity can be affected by:

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TEMPERATURE & ENZYME ACTIVITY

Each enzyme has an optimal temperature at which it can function (Usually near body temp)

http://www.animated-gifs.eu/meteo-thermometers/001.htm

Increasing temperature increases the rate of an enzyme-catalyzed reaction up to a point.Above a certain temperature, activity begins to decline because the enzyme begins to _________.

http://www.uic.edu/classes/bios/bios100/lectures/chemistry.htm

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pH and ENZYME ACTIVITYEach enzyme has an optimal pH at which it can

function

_________________= non-protein enzyme helpers

• EX: Zinc, iron, copper

_________________= organic enzyme helpers

• Ex: vitamins

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http://www.elmhurst.edu/~chm/vchembook/595FADcoq.html

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SUBSTRATE CONCENTRATION & ENZYME ACTIVITY

V MAX←

Adding substrate increases activity _____________

REGULATION OF ENZYME PATHWAYS

• _________________cell switches _________ the ______ that code for specific enzymes

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REGULATION OF ENZYME PATHWAYS• FEEDBACK INHIBITION

end product of a pathway interacts with and “turns off” an enzyme earlier in pathway

• prevents a cell from wasting chemical resources by synthesizing more product than is needed

FEEDBACK INHIBITION

NEGATIVE FEEDBACK

– An accumulation of an end product slows the process that produces that product

B

A

C

D

Enzyme 1Enzyme 1

Enzyme 2

Enzyme 3

DD D D

D

D

DDDD

C

B

A Negativefeedback

Example: sugar breakdown generates ATP; excess ATP inhibits an enzyme near the beginning of the pathway

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POSITIVE FEEDBACK (less common)

– The end product speeds up productionWW

X

Y

ZZ

Z

ZZ

Z

Z Z Z

Z Z Z Z

ZZZ Z

ZZ

Y

X

Enzyme 4

Enzyme 5

Enzyme 6

Enzyme 4

Enzyme 5

Enzyme 6

Positivefeedback

EXAMPLE: Chemicals released by platelets that accumulate at injury site, attract MORE platelets to the site.

REGULATION OF ENZYME ACTIVITY• __________________________

protein’s function at one site is affected by binding of a regulatory molecule at another site

• Allosteric regulation can inhibit or stimulate an enzyme’s activity

http://bio.winona.edu/berg/ANIMTNS/allostan.gif

Allosteric enzyme inhibition

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SOME ALLOSTERIC ENZYMES HAVE MULTIPLE SUBUNITS

• Each enzyme has active and inactive forms

• The binding of an _________ stabilizes the active form

• The binding of an _________ stabilizes the inactive form

Substrate

Binding of one substrate molecule toactive site of one subunit locks allsubunits in active conformation.

Cooperativity another type of allosteric activationStabilized active formInactive form

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______________________= form of allosteric regulation that can _______enzyme activity

Binding of one substrate to active site of one subunit locks all subunits in active conformation

___________________ inhibitor ___________; Mimics substrate and competes with substrate for active site on enzyme

ENZYMEANIMATION

Enzyme Inhibitors

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Enzyme Inhibitors_______________ inhibitors bind to another

part of an enzyme, causing the enzyme to change shape and making the active site less effective

ENZYMEANIMATION