MetabolismMetabolism

Cell EnergeticsCell Energetics

Cell do three Cell do three mainmain kinds of work kinds of work Mechanical – move themselvesMechanical – move themselves Transport – move something elseTransport – move something else Chemical – convert stuff to other stuffChemical – convert stuff to other stuff

Work requires energyWork requires energy Where does the energy come from and Where does the energy come from and

how do cells use it?how do cells use it?

Cell EnergeticsCell Energetics

Energy is ______Energy is ______ Metabolism Metabolism 2 types of metabolism2 types of metabolism Two forms of energyTwo forms of energy

How do cells use the 2 formsHow do cells use the 2 forms 2 Laws of Thermodynamics2 Laws of Thermodynamics Entropy Entropy 2 types of reactions 2 types of reactions

Cell EnergeticsCell Energetics

MetabolismMetabolism = total of all the = total of all the chemical reactions taking place in chemical reactions taking place in

an organisman organism

MetabolismMetabolism

AnabolismAnabolism = ‘= ‘build up’ processes; build up’ processes; ‘consume’ (store) energy by ‘consume’ (store) energy by assembling macromolecules assembling macromolecules PhotosynthesisPhotosynthesis

CatabolismCatabolism = ‘break down’ = ‘break down’ reactions; release energy by reactions; release energy by breaking down (lyse) molecules breaking down (lyse) molecules DigestionDigestion

EnergyEnergy

Energy – the ability to do workEnergy – the ability to do work PotentialPotential = capacity to do = capacity to do

work (move something); due work (move something); due to to positionposition or stored (chemical or stored (chemical energy; glucose, glycogen)energy; glucose, glycogen)

KineticKinetic = motion = motion EquilibriumEquilibrium = energy runs out = energy runs out

Kinetic and potential energyKinetic and potential energy

What does the types of energy have to do with biology?

Thermodynamics Thermodynamics

11stst Law – energy cannot be created nor Law – energy cannot be created nor destroyeddestroyed Energy Energy cancan be transformed be transformed

22ndnd Law – ‘Law of Law – ‘Law of EntropyEntropy’ whenever energy is ’ whenever energy is transformed, some of it becomes ‘unusable’transformed, some of it becomes ‘unusable’

Entropy - Entropy - amount of usable energy decreases amount of usable energy decreases each time it is usedeach time it is used ‘‘Lost’ as heatLost’ as heat Energy is running down, universe is tending Energy is running down, universe is tending

towards disordertowards disorder

Biological Order and DisorderBiological Order and Disorder

Organisms are Organisms are openopen systems systems Use energy to maintain order and Use energy to maintain order and

organization organization Trade organization for heat (increase Trade organization for heat (increase

entropy in the environment)entropy in the environment)

Metabolism: ReactionsMetabolism: Reactions Two types of reactions:Two types of reactions:

Exergonic, endergonic Exergonic, endergonic Exergonic reactionExergonic reaction - - release of free release of free

energyenergy Less stable, more workLess stable, more work Fire, respiration Fire, respiration

Metabolism: ReactionsMetabolism: Reactions

Endergonic reactionEndergonic reaction - - energy is energy is absorbed/storedabsorbed/stored Photosynthesis Photosynthesis

Chemical ReactionsChemical Reactions

Equilibrium is Equilibrium is eventually eventually reached in closed reached in closed systemssystems Reduced free Reduced free

energyenergy No work is doneNo work is done You’re dead!You’re dead!

What cells do..

ReviewReview

What are the 2 forms of energy?What are the 2 forms of energy? _____ is the ability to do work_____ is the ability to do work Energy is lost in chemical reactions as __Energy is lost in chemical reactions as __ A reaction that stores/absorbs energy is A reaction that stores/absorbs energy is

said to be _____said to be _____ A reaction that releases energy is _____A reaction that releases energy is _____ The total of all chemical reactions in an The total of all chemical reactions in an

organism is called ____organism is called ____

Coupled ReactionsCoupled Reactions Living systems use coupled Living systems use coupled

reactions reactions Endergonic reactions are linked Endergonic reactions are linked

((coupledcoupled) with exergonic reactions) with exergonic reactions Energy from an exergonic reaction Energy from an exergonic reaction

(respiration) is stored in chemical (respiration) is stored in chemical bondsbonds

Coupled ReactionsCoupled Reactions

ATP – Adenosine triphosphateATP – Adenosine triphosphate Cyclical Cyclical Catabolic pathways drive the Catabolic pathways drive the

regeneration of ATP from ADP and regeneration of ATP from ADP and phosphatephosphate

Controlled by Controlled by enzymesenzymes

Uses of EnergyUses of Energy

Mechanical -Mechanical - moving of moving of cilia/flagella, muscle, cilia/flagella, muscle, cytoplasm, chromosomes cytoplasm, chromosomes (mitosis), mousetrap(mitosis), mousetrap

Transport -Transport - H+ ‘pump’, receptors H+ ‘pump’, receptors Chemical –Chemical – polymerization polymerization

BioluminescenceBioluminescence

• EnzymesEnzymes controlcontrol metabolism – metabolism – If enzymes are present, If enzymes are present, reactions take place, if not, reactions take place, if not, they don’t.they don’t.Enzymes speed up reactions by Enzymes speed up reactions by lowering activation energylowering activation energy

Biological catalystsBiological catalysts Accelerate a reaction without being Accelerate a reaction without being

changed changed Proteins (700)Proteins (700)

Catabolic or anabolic reactionsCatabolic or anabolic reactions

EnzymesEnzymes

Enzymes Enzymes All chemical reactions require All chemical reactions require

activation energyactivation energy Activation energy (EActivation energy (EAA)) - the - the

initial amount of energy needed initial amount of energy needed to start a chemical reaction to start a chemical reaction

Transition stateTransition state = reactants have absorbed = reactants have absorbed energyenergy Have become unstableHave become unstable Reaction takes placeReaction takes place

EnzymeEnzymess Some reactions occur Some reactions occur

spontaneously due to spontaneously due to heat from the heat from the environment (rust)environment (rust)

Cellular T needs to Cellular T needs to remain lowremain low

Metabolism is too slow at Metabolism is too slow at low Tlow T Starch to glucoseStarch to glucose

EnzymesEnzymes used to used to reducereduce activation energy activation energy (metabolism at lower T)(metabolism at lower T)

EnzymesEnzymes SubstrateSubstrate = substance enzyme acts on = substance enzyme acts on Active siteActive site = area on the enzyme where = area on the enzyme where

substrate binds substrate binds Verryyy specificVerryyy specific Groove, pocket = 3d shapeGroove, pocket = 3d shape

EnzymesEnzymes Lock and key mechanismLock and key mechanism Induced FitInduced Fit = enzyme may change shape = enzyme may change shape

to allow better reaction on substrateto allow better reaction on substrate

Factors That Affect Enzyme Factors That Affect Enzyme Activity Activity

TemperatureTemperature pHpH Inorganic salts – Inorganic salts –

Disrupt H bonds, ionic bonds, Disrupt H bonds, ionic bonds, hydrophobic interactionshydrophobic interactions

CofactorsCofactors InhibitorsInhibitors

Temperature and pH affect

enzyme activity

CofactorsCofactors

Cofactors - nonprotein enzyme Cofactors - nonprotein enzyme helpershelpers Metals – Fe, Zn, CuMetals – Fe, Zn, Cu

Coenzymes - organic cofactorsCoenzymes - organic cofactors Vitamins Vitamins

InhibitorsInhibitors = substances that inhibit = substances that inhibit the actions of enzymes (2 kinds:)the actions of enzymes (2 kinds:) Competitive inhibitorsCompetitive inhibitors Noncompetitive inhibitorsNoncompetitive inhibitors

EnzymesEnzymes

Competitive inhibitors - resemble substrate, block active site Neurotoxin, Disulfiram

Noncompetitive Noncompetitive inhibitors - inhibitors - causes causes enzyme to change enzyme to change shapeshape Destroys Destroys

conformation (active conformation (active site)site)

DDT, nerve gas (DSF)DDT, nerve gas (DSF) May be May be allosteric allosteric

regulationregulation

EnzymesEnzymes

Allosteric Regulation of Allosteric Regulation of EnzymesEnzymes

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

Receptor siteReceptor site located away from located away from the active site (quatenary the active site (quatenary structure)structure)

Allosteric site has to be Allosteric site has to be activated, (may be inhibited)activated, (may be inhibited)

Allosteric activator

Allosteric inhibitor

Cooperativity -Cooperativity - oneone substrate molecule substrate molecule can activate all other can activate all other subunits of an enzymesubunits of an enzyme Induced fitInduced fit

Only requires a small Only requires a small concentration of concentration of substrate to activate substrate to activate enzymeenzyme

EnzymesEnzymes

Enzyme Activity Helps Control Enzyme Activity Helps Control MetabolismMetabolism

A cell’s metabolic pathways must be A cell’s metabolic pathways must be tightly regulatedtightly regulated

DNA codes for proteins (enzymes)DNA codes for proteins (enzymes) Amount of enzyme can determine Amount of enzyme can determine

rate of reactionrate of reaction Feedback Inhibition - Feedback Inhibition - end product of end product of

the pathway inhibits the pathwaythe pathway inhibits the pathway

Regulation Regulation

Metabolic pathways – series of enzymes Metabolic pathways – series of enzymes creates small steps to a final productcreates small steps to a final product

Controlling the enzymes (activity or Controlling the enzymes (activity or production) controls the pathway and production) controls the pathway and product(s)product(s)

Feedback InhibitionFeedback Inhibition

Final product of the Final product of the pathway shuts off the pathway shuts off the pathwaypathway

Feedback inhibition Feedback inhibition prevents cells from prevents cells from wasting resourceswasting resources ““don’t need gas if you don’t need gas if you

don’t have a car.”don’t have a car.”

Isoleucine – allosteric inhibitor