Marvelous MetabolismMarvelous Metabolism

Chapter 8Chapter 8

I. Vivacious VocabularyI. Vivacious Vocabulary

Metabolism - total of all an organisms chemical Metabolism - total of all an organisms chemical processes (all the reactions happening in an processes (all the reactions happening in an organism)organism)Catabolic pathways - release energy by breaking Catabolic pathways - release energy by breaking down complex molecules into simpler onesdown complex molecules into simpler ones

ex. - respirationex. - respirationAnabolic pathways - consume energy to build Anabolic pathways - consume energy to build complex molecules from simpler onescomplex molecules from simpler ones

ex. - building proteins from amino acidsex. - building proteins from amino acidsBioenergetics - study of how organisms manage Bioenergetics - study of how organisms manage their energy resourcestheir energy resources

II. EnergyII. Energy

Capacity to do workCapacity to do work

A. Kinetic energy A. Kinetic energy

Energy of motionEnergy of motion

Ex.Ex.– Water through damWater through dam– Light powering photosynthesisLight powering photosynthesis– Heat is kinetic energy associated with Heat is kinetic energy associated with

RANDOM movement of atoms.RANDOM movement of atoms.

B. Potential energy B. Potential energy

Stored energy due to location or structureStored energy due to location or structure

Ex.Ex.– Water behind dam (before it’s released)Water behind dam (before it’s released)

– Chemical energyChemical energy - stored in - stored in molecules due to arrangement of molecules due to arrangement of atomsatoms

Organisms are energy transformers!!Organisms are energy transformers!!

III. ThermodynamicsIII. Thermodynamics

Study of energy transformationsStudy of energy transformations

III. ThermodynamicsIII. Thermodynamics

A. First Law of Thermodynamics - energy A. First Law of Thermodynamics - energy can not be created or destroyed, but it can can not be created or destroyed, but it can be transferredbe transferredB. Second Law of Thermodynamics - B. Second Law of Thermodynamics - Every energy transfer increases the Every energy transfer increases the entropy (disorder/ randomness) of the entropy (disorder/ randomness) of the universeuniverse– 1. In most energy transformations, part of the 1. In most energy transformations, part of the

energy is lost as heat (heat is energy in it’s energy is lost as heat (heat is energy in it’s most random state)most random state)

– 2. Entropy of a system can decrease, as long 2. Entropy of a system can decrease, as long as the entropy of the universe (system+ as the entropy of the universe (system+ surroundings) increases surroundings) increases

IV. Free Energy IV. Free Energy

Portion of a system’s energy that can Portion of a system’s energy that can perform work when temperature is perform work when temperature is uniform throughout the systemuniform throughout the system

G = G = H - T H - T SS G = change in free energyG = change in free energy H = change in system total energyH = change in system total energy

T = absolute temp (in Kelvin T = absolute temp (in Kelvin ooC + 273)C + 273)S = change in entropyS = change in entropy

IV. Free EnergyIV. Free Energy

In any spontaneous process, the free In any spontaneous process, the free energy of a system decreases energy of a system decreases

((G must be negative)G must be negative)

For a reaction at equilibrium, For a reaction at equilibrium, G = 0G = 0

A. Exergonic reactionA. Exergonic reaction

Energy OutEnergy Out - occur with a release of free energy - occur with a release of free energy

--G = spontaneous reactionG = spontaneous reaction

ex. - Cellular respirationex. - Cellular respiration

CC66HH1212OO66 + 6O + 6O22 ---->6CO ---->6CO2 2 + 6H+ 6H22OO

G = -686 kcal/moleG = -686 kcal/mole

B. Endergonic reaction B. Endergonic reaction

Energy InEnergy In- absorbs free energy from it’s - absorbs free energy from it’s surroundings surroundings + + G = nonspontaneous reactionG = nonspontaneous reaction

ex - Photosynthesis ex - Photosynthesis G = +686 kcal/moleG = +686 kcal/mole

This reaction is powered by light This reaction is powered by light energy from the sunenergy from the sun

C. Metabolic DisequilibriumC. Metabolic Disequilibrium

If a cell were allowed to reach If a cell were allowed to reach chemical equilibrium, chemical equilibrium, G = 0, the G = 0, the cell would be dead. To keep this cell would be dead. To keep this from happening, the product of one from happening, the product of one reaction becomes a reactant for reaction becomes a reactant for another reaction. This keeps another reaction. This keeps products from building up and products from building up and prevents the cell from reaching prevents the cell from reaching equilibrium.equilibrium.

V. Awesome ATPV. Awesome ATP

A.A. Types of Work - cells do three types Types of Work - cells do three types of workof work

1.1. MechanicalMechanical - muscle contraction, - muscle contraction, movement of chromosomesmovement of chromosomes

2.2. Transport Transport - pumping across - pumping across membranesmembranes

3.3. ChemicalChemical - pushing endergonic - pushing endergonic reactions that would not occur reactions that would not occur spontaneouslyspontaneously

V. Awesome ATPV. Awesome ATP

B.B. ATP - source of energy that powers ATP - source of energy that powers cellular workcellular workAdenosine triphosphate (adenine + Adenosine triphosphate (adenine + ribose + 3 phosphate)ribose + 3 phosphate)

1.1. Bonds between phosphate groups Bonds between phosphate groups can be broken by can be broken by hydrolysishydrolysis. This . This releases energy releases energy G = -7.3 kcal/mol G = -7.3 kcal/mol

ATP + H2O ----> ADP + PiATP + H2O ----> ADP + Pi

V. Awesome ATPV. Awesome ATP

When ATP is hydrolyzed (broken When ATP is hydrolyzed (broken down), it can be used to drive down), it can be used to drive endergonic reactions by endergonic reactions by transferring the Pi (phosphate) transferring the Pi (phosphate) group to some other molecule. This group to some other molecule. This is called Phosphorylation. is called Phosphorylation.

V. Awesome ATPV. Awesome ATP

ATP can also be regenerated by ATP can also be regenerated by adding a Pi to ADP. adding a Pi to ADP.

This is an This is an endergonicendergonic reaction. reaction.

G = +7.3 kcal/molG = +7.3 kcal/mol

This reaction happens continuously This reaction happens continuously in a cell and is driven by breaking in a cell and is driven by breaking down glucose in respiration.down glucose in respiration.

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Exciting and Exciting and Energetic Energetic

Enzymes!!!Enzymes!!!

I. What are Enzymes?I. What are Enzymes?

Enzymes are protein catalysts!!Enzymes are protein catalysts!!

Catalysts speed up the rate of a Catalysts speed up the rate of a reaction without being consumed!reaction without being consumed!

II. Remember Free Energy?II. Remember Free Energy?

Activation Energy EActivation Energy EAA

– Free Energy needed to start a reactionFree Energy needed to start a reaction– Required to break bonds of reactantsRequired to break bonds of reactants– Heat works! It speeds up the molecules, Heat works! It speeds up the molecules,

which collide more and strongerwhich collide more and stronger

III. How do Enzymes Work?III. How do Enzymes Work?

Heat doesn’t work for cells because it Heat doesn’t work for cells because it denatures proteins...so...Go denatures proteins...so...Go Enzymes!Enzymes!

Enzymes lower EA barrier so transition Enzymes lower EA barrier so transition state can be reached at room temperaturestate can be reached at room temperature

Only can speed up reactions that would Only can speed up reactions that would occur anywayoccur anyway

Enzymes work on a specific substrate or Enzymes work on a specific substrate or reactantreactant

III. How do Enzymes Work?III. How do Enzymes Work?

EnzymeEnzymeSubstrate ---------------- > Product(s)Substrate ---------------- > Product(s)

SucraseSucrase

Sucrose + HSucrose + H220 ------------- > Glucose + 0 ------------- > Glucose + FructoseFructose

Enzymes are so specific, can distinguish Enzymes are so specific, can distinguish between isomersbetween isomersEnzymes usually end in -aseEnzymes usually end in -ase

Figure 6.11 Example of an enzyme-catalyzed reaction: Hydrolysis of sucroseFigure 6.11 Example of an enzyme-catalyzed reaction: Hydrolysis of sucrose

IV. The Detail and the VisualIV. The Detail and the Visual

Enzymes have active sites where the Enzymes have active sites where the substrate fits!substrate fits!When substrate enters the active When substrate enters the active site, it induces the enzyme to change site, it induces the enzyme to change shape slightly so it’s nice and snug. shape slightly so it’s nice and snug. This is an induced fit. (Big H-bond This is an induced fit. (Big H-bond Hug!)Hug!)About 1000 substrate About 1000 substrate molecules/second or moremolecules/second or more

Figure 6.14 The induced fit between an enzyme and its substrateFigure 6.14 The induced fit between an enzyme and its substrate

V. How do enzymes do these V. How do enzymes do these cool things?cool things?

Can stress or twist bonds to induce a break! (less Can stress or twist bonds to induce a break! (less heat will be required)heat will be required)Active site may give a micro environmentActive site may give a micro environment– Lower pHLower pH– Brief covalent bonds with side chains of the enzymeBrief covalent bonds with side chains of the enzyme

The more substrate, the faster the reaction The more substrate, the faster the reaction occurs until the saturation point where enough to occurs until the saturation point where enough to fill each enzyme (vmax)fill each enzyme (vmax)Sometimes Cofactors (coenzymes) requiredSometimes Cofactors (coenzymes) required

-non-protein helpers, vitamins, minerals-non-protein helpers, vitamins, minerals

VI.VI. Environment can changeEnvironment can change A LOT! A LOT!

Enzymes have an optimal Enzymes have an optimal temperature and pHtemperature and pH

Temperature increases the speed of Temperature increases the speed of reactions with enzymes....the reactions with enzymes....the molecules move fastermolecules move faster

Too high a temp and the protein Too high a temp and the protein enzymes denature and don’t work enzymes denature and don’t work

VII. Evil Enzyme InhibitorsVII. Evil Enzyme Inhibitors

Competitive Inhibitors:Competitive Inhibitors:– Mimic the normal substrate and compete for Mimic the normal substrate and compete for

admission into active site.admission into active site.

Non-competitive InhibitorNon-competitive Inhibitor– Bind to enzyme somewhere other than active Bind to enzyme somewhere other than active

site, change shape of enzyme so substrate site, change shape of enzyme so substrate doesn’t fit.doesn’t fit.

Bad inhibitors include...DDT (pesticides) Bad inhibitors include...DDT (pesticides) and Antibiotics (inhibit bacteria)and Antibiotics (inhibit bacteria)

VIII. RegulatorsVIII. Regulators

Enzymes often have regulator molecules! Enzymes often have regulator molecules! These bond to an allosteric site (away These bond to an allosteric site (away from active site)from active site)

Enzyme has two shapes...1 active and 1 Enzyme has two shapes...1 active and 1 inactiveinactive

Activators bind to allosteric site and Activators bind to allosteric site and stabilize the active shapestabilize the active shape

Inhibitors bind to allosteric site and causes Inhibitors bind to allosteric site and causes enzymes inactive shapeenzymes inactive shape

VIII. RegulatorsVIII. Regulators

Feedback InhibitionFeedback Inhibition– Metabolic path is shut off because the Metabolic path is shut off because the

end-product acts as an inhibitor by end-product acts as an inhibitor by allosterically bindingallosterically binding

– This prevents wasting resources when This prevents wasting resources when there is enough productthere is enough product

IX. Order! Order!IX. Order! Order!

It’s not just random soup out there in cell It’s not just random soup out there in cell land!land!Enzyme teams hang out together in a Enzyme teams hang out together in a multienzyme complexmultienzyme complexSome enzymes are in fixed locations in the Some enzymes are in fixed locations in the cell as fixtures in membranescell as fixtures in membranesSome are in solution inside organellesSome are in solution inside organelles– Respiration enzymes are in Mighty Respiration enzymes are in Mighty

MitochondriaMitochondria

Emergent Properties Rule!!Emergent Properties Rule!!