OpenerOpener: Wednesday, 9/28: Wednesday, 9/28Compare & contrast these Compare & contrast these

molecules--# bonds, elements, molecules--# bonds, elements, etc.:etc.:

CarbohydratesCarbohydrates

ProteinProtein

LipidLipid

2.4 KEY CONCEPT 2.4 KEY CONCEPT Life depends on chemical Life depends on chemical reactions!reactions!

Oh Snap! Remember this Oh Snap! Remember this from PHY SCI???from PHY SCI???

• Mg + 2HMg + 2H22O --> Mg(OH)O --> Mg(OH)

22 + H + H22

Reactants ProductsReactants Products

• Mg + 2HMg + 2H22O --> Mg(OH)O --> Mg(OH)

22 + H + H22

Coefficients SubscriptsCoefficients Subscripts

Bonds break & form during chemical Bonds break & form during chemical reactions!reactions!

-allows organisms to grow, develop, -allows organisms to grow, develop, reproduce, and adapt.reproduce, and adapt.

--breaks downbreaks down some substances & some substances & formsforms othersothers

Reactants Yields(Makes)

Products

COCO22 + H + H22O O HH22COCO33

• Bond energyBond energy = amount of = amount of energy that breaks a bond! energy that breaks a bond!

• EquilibriumEquilibrium = when reactants = when reactants and products form at the and products form at the same rate.same rate.

Activation energyActivation energy!!!!!!amount of energy needed for a amount of energy needed for a particular chemical reaction to particular chemical reaction to

occur!!occur!!

Activation Energy:

ExoExothermicthermic reactions reactions releaserelease more more energy than they absorb!energy than they absorb!

– Reactants higher bond energies than Reactants higher bond energies than productsproducts

– Excess energy is Excess energy is RELEASEDRELEASED by reaction. by reaction.

EndoEndothermicthermic reactions reactions absorbabsorb more more energy than they release!energy than they release!

– Reactants- lower bond energies than Reactants- lower bond energies than productsproducts

– Energy Energy ABSORBEDABSORBED by reaction by reaction

Energy (absorbed or Energy (absorbed or released) can be in the released) can be in the form of:form of:

-heat -heat

-light-light

pH is important…pH is important…why?why?

• measures acidity of solutionmeasures acidity of solution• Normal limits: Normal limits: narrownarrow range! range!• Buffers: regulate pH Buffers: regulate pH (blood, seawater)(blood, seawater)

• Small change = BIG DEAL!!!!Small change = BIG DEAL!!!!• 4 -5 on pH scale 4 -5 on pH scale

10x more acidic!! OUCH!!10x more acidic!! OUCH!!

Pineapple Pineapple Enzyme LabEnzyme Lab• Set up today

• Results tomorrow

• Test FRIDAY!!

Happy Thursday! Happy Thursday! 9/299/29

• Test Friday!Test Friday!• Please list Please list • THREE questions that you haveTHREE questions that you have• TWO things you’re sure aboutTWO things you’re sure about• ONE thing you want to know ONE thing you want to know

about ENERGY that we didn’t about ENERGY that we didn’t learn!learn!

2.5 KEY CONCEPT2.5 KEY CONCEPTEnzymes are catalysts for Enzymes are catalysts for chemical reactions in living chemical reactions in living things!things!

CatalystCatalyst (speeds up rxn rate)(speeds up rxn rate)

1. Lowers Act. En., speeds up 1. Lowers Act. En., speeds up reaction ratereaction rate

2. Not used up (reused over & 2. Not used up (reused over & over)over)

EnzymesEnzymes::--Proteins = biological catalysts Proteins = biological catalysts -Help -Help manymany chemical rxns chemical rxns

-(live, reproduce, grow) -(live, reproduce, grow)(digestion, respiration, reproduction, (digestion, respiration, reproduction,

movement & cell regulation)movement & cell regulation)

Enzyme structure & Enzyme structure & functionfunction

--Each Each particularparticular enzyme can enzyme can catalyze only catalyze only oneone chemical chemical reaction!!!reaction!!!

Structure can be altered by:Structure can be altered by: - - temperaturetemperature - - pHpH

“Optimal” Temp, “Optimal” pH“Optimal” Temp, “Optimal” pH

If Out of range If Out of range broken down, broken down, messed up…“messed up…“DenaturedDenatured” ”

High fever = dangerous, enzymes in body can’t High fever = dangerous, enzymes in body can’t function at high temps!!!function at high temps!!!

Enzyme Structure Can Be Altered by:

Homeostasis & Homeostasis & Enzymes!Enzymes!

-Function best w/in small -Function best w/in small range of conditions.range of conditions.

– Changes in temp & pH can Changes in temp & pH can break H bonds!break H bonds!

– Function Function dependsdepends on its on its structure...so…structure...so…

Structure allows only certain things to Structure allows only certain things to bind!!!bind!!!– Substrates = specific reactants enzymes act on!

Ex. Amylase (enzyme) only works on starch (substrate)

– Active site – where substrate binds to enzyme

substrates (reactants)

enzyme

Substrates bind to anenzyme at certain places called active sites.

The lock-and-key model:The lock-and-key model:

illustrates illustrates howhow enzymes enzymes function!function!– substrates brought togethersubstrates brought together

– bonds break/formbonds break/form– Product is made, released from Product is made, released from

enzymeenzyme– Enzyme is REUSEDEnzyme is REUSED

Let’s DRAW IT!Let’s DRAW IT!

Lock:Lock:

Key:Key: Substrates bind to anenzyme at certain places called active sites.

The enzyme bringssubstrates together and weakens their bonds.

The catalyzed reaction formsa product that is releasedfrom the enzyme.

New food recommendations—not a pyramid!

• http://www.choosemyplate.gov/

Pineapple Pineapple Enzyme LabEnzyme Lab• Results

• Test TOMORROW!!

• Go over Ch 4 Quiz afterGo over Ch 4 Quiz after

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