ENERGY!!!!! WHERE DOES IT COME FROM??????

What do you think of when you think of a chemical reaction?

Chemical Reactions

Change substances into different substances by breaking and forming chemical bonds.

Can you name any reactions.

NaHCO3(s) +HC2H3O2(aq) =>H2O +

CO2(g) + NaC2H3O2(aq)

Can You Think of Any Reactions in Your Body?

Where to you think oxygen and carbon dioxide come from?

Chemical Equations

REACTANTS PRODUCTS

Needs energyto start reactions!!!

Parts of an Equation All chemical reactions…

have two parts:1. Reactants = the substances you start with2. Products = the substances you end up with

The reactants will turn into the products.

Reactants Products

TAKES ENERGY TO GET A REACTION GOING!! Most of the time!!

What gets photosynthesis going? Where does the energy come from? Where does energy exist in the equation?

Basic Revision For a chemical reaction to occur, bonds must

be both formed and broken

Fe + CuSO4 Cu + FeSO4

Bond Energy BOND ENERGY :Amount of energy needed

to break the bonds between molecules. Energy is needed to break bonds. The

stronger the bond the more energy needed. The amount of energy is different for all bonds.

Energy is released when bonds are formed like with H and O to make water.

Activation Energy

Energy needed to get the reaction started.

Photosynthesis: sunlight

Fuel: match

Bond EnergyIf the SAME NUMBER of bonds are made and broken, how can energy be given out in an exothermic reaction?

The answer is that different chemical bonds have different amounts of energy in them.

Carbon is joined to a hydrogen by a strong bond. 412 kJ of energy is needed to break this bond, and to separate the atoms The same amount of energy is given out when the bond is formed.

H O has a bond energy of 463 kJ

C==O has a bond energy of 743 kJ

Chemical Reaction either absorb or release energyReactants: energy needed to break bonds.

Energy added to break bonds.

Products: form bonds so energy is released.

If subtract the amount of energy released and needed, sometimes there if more energy released and other times there is energy absorbed

Exothermic and Endothermic Reactions A reaction in which heat or more energy is

produced is given out is exothermic.

A reaction in which heat is taken in or more energy is used is endothermic.

Energy is needed to break bonds apart.

Energy is released when bonds are formed.

So how do exothermic reactions give out energy to the surroundings?

Exothermic Reactions

ENERGY AND CHEMICAL REACTIONSExothermic reactions These reactions give out heat energy. Combustion is an exothermic reaction.

Exothermic reactions Chemical reaction where more energy is

released than it absorbs Difference in energy between reactant and

products. Usually heat or light. EX: Cellular respiration

These are drawn as graphs.

The x axis shows time, the y axis shows energy.

Energy

Time

Energy Level Diagrams

They are used to show exothermic and endothermic reactions.

Activation EnergyMost exothermic reactions need a bit of energy to get them started, like lighting methane with a match.

This energy is known as ACTIVATION ENERGY. This energy breaks the bonds and allows atoms to separate.This changes the shape of the energy diagram to

this.

Energy

Time

reactants

products

} Activation energy

Exothermic ReactionsAn exothermic energy diagram looks like this.

Energy

Time

reactants

products

Energy released}

Exothermic ReactionsCombustion and respiration are exothermic reactions. e.g. burning methane (natural gas).

CH4 + 2O2 2H2O + CO2

Energy

Time

2H2O + CO2

Energy released

}CH4 + 2O2

Exothermic Reaction

ENERGY AND CHEMICAL REACTIONSEndothermic reactions These reactions take in heat energy from their

surroundings. These cause temperatures to fall. They get

cold!!!

Endothermic ReactionsIn these reactions, the energy required for

bond breaking IS GREATER than the energy released by bond making.

This means that to make endothermic reactions take place, extra energy is

needed from an external source.

Endothermic reactions Chemical reaction where more energy is

absorbed than released. Energy must be absorbed to make up

difference between reactants and products EX: photosynthesis Traps energy in bonds of

glucose

Endothermic ReactionsExamples are photosynthesis and most electrolysis reactions.

The energy level diagrams look like this.

Energy

Time

reactants

products

} Energy needed to make the reaction work.

Endothermic Reaction

When trying to classify a process as exothermic or endothermic, watch how the temperature of the surroundings changes. An exothermic process releases heat, and causes the temperature of the immediate surroundings to rise. An endothermic process absorbs heat and cools the surroundings. Can you think of a way to test the classification of each of these processes?

Exothermic processes - gives off energy Endothermic processes- takes in energy

making ice cubes melting ice cubes formation of snow in clouds conversion of frost to water vapor condensation of rain from water vapor evaporation of water a candle flame mixing sodium sulfite and bleach baking bread rusting iron cooking an egg burning sugar producing sugar by photosynthesis forming ion pairs separating ion pairs Combining atoms to make gas splitting a gas molecule apart mixing water and strong acids mixing water and ammonium nitrate mixing water with an anhydrous salt crystallizing liquid salts in chemical handwarmers) melting solid salts nuclear fission reaction of barium hydroxide octahydrate crystals with dry ammonium chloride

Activation Energy Energy needed to get the reaction started.

Some reaction takes more energy than others. Usually this is increasing the temperature but organisms cannot change the temperature so something else has to help decrease the amount of energy needed. We cannot use all our energy for reactions like photosynthesis and respiration.

Increase of Temperature Can organisms have a great increase in

temperature? Need other ways to get increase or to decrease

the amount of activation energy needed This is where catalysts come into play.

CATALYST A substance that decreases the activation

energy needed to start a reaction. Usually temperature increase but organisms cannot have a great increase in temperature or die

Increases the rate of reaction or speed of reactions.

They break the bonds between the reactants to speed up the reaction.

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EnzymesEnzymes

ENZYMES*A type of protein that acts as a catalyst which lowers activation energy needed to start a reaction.

*They speed up reactions by weaken bonds.

*Always in in -ase

© 2007 Paul Billiet ODWS

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What Are Enzymes?What Are Enzymes? Most enzymes are

Proteins Proteins ((tertiary and quaternary structures)

Act as CatalystCatalyst to accelerates a reaction

Not permanentlyNot permanently changed in the process

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How do enzymes How do enzymes Work?Work?Enzymes work by weakening weakening bondsbonds which which lowers lowers activation activation energyenergy

Enzyme structure Enzymes are

proteins They have a

globular shape A complex 3-D

structure

.

© 2007 Paul Billiet ODWS

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EnzymesEnzymes Are specific

for what they will catalyzecatalyze

Are ReusableReusable End in –asease

-Sucrase-Sucrase-Lactase-Lactase-Maltase-Maltase

The substrate The substrate of an enzyme are the reactants

that are acted on by the enzyme. Enzymes are specific to their substrates The specificity is determined by the active

site ENZYMES ARE SHAPED TO FIT ONLY

THEIR SUBTRATE BECAUSE THEIR ACTIVE SITE IS SHAPED TO FIT ONLY ONE SUBSTRATE!!!!© 2007 Paul Billiet ODWS

The active sitePLACE WHERE

SUBSTRATE FITS!!

ONLY THE ONE SUBTRATE WILL FIT!!!

© H.PELLETIER, M.R.SAWAYA ProNuC Database

© 2007 Paul Billiet ODWS

Enzyme Structure It fits like a lock and key with its subtrate.

Will not fit any other substance. How Works 1. Enzyme brings molecules close together. 2. By bonding they have weaken the bonds of

the subtrate so they reaction can occur quicker.

An enzyme controlled pathway

© 2007 Paul Billiet ODWS

The Lock and Key Hypothesis Fit between the substrate and the active site of the

enzyme is exact Like a key fits into a lock very precisely The key is analogous to the enzyme and the substrate

analogous to the lock. Temporary structure called the enzyme-substrate

complex formed

© 2007 Paul Billiet ODWS

The Lock and Key Hypothesis This explains enzyme specificity This explains the loss of activity when

enzymes denature

© 2007 Paul Billiet ODWS

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EnzymesEnzymes

FreeEnergy

Progress of the reaction

Reactants

Products

Free energy of activationFree energy of activation

Without Enzyme

With Enzyme

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Enzyme-Substrate Enzyme-Substrate ComplexComplex

The substancesubstance (reactant) an enzymeenzyme acts on is the substratesubstrate

EnzymeSubstrate Joins

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Active SiteActive Site A restricted regionrestricted region of an enzymeenzyme

molecule which bindsbinds to the substratesubstrate.

Enzyme

SubstrateActive Site

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Induced FitInduced Fit A change in

the shapeshape of an enzyme’s active site

Induced Induced by the substrate

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Induced FitInduced Fit A changechange in the configurationconfiguration

of an enzyme’s activeenzyme’s active site site (H+ and ionic bonds are involved).

InducedInduced by the substratesubstrate..

Enzyme

Active Sitesubstrate

induced fit

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What Affects Enzyme What Affects Enzyme Activity?Activity?

Three factors:Three factors:1.1. Environmental ConditionsEnvironmental Conditions

2.2. Cofactors and CoenzymesCofactors and Coenzymes

3.3. Enzyme InhibitorsEnzyme Inhibitors

Denaturing of Enzymes Denaturing: enzyme structure can be

destroyed by many different factors.

1. pH

2. Temperature

3. Inhibitors(like poison)

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1. Environmental 1. Environmental ConditionsConditions

A.A. Extreme Extreme Temperature Temperature are the are the most dangerous most dangerous high tempshigh temps may denature (unfold) denature (unfold) the enzyme. enzyme.

B. B. pHpH (most like 6 - 8 pH near (most like 6 - 8 pH near neutral)neutral)C. C. Ionic concentrationIonic concentration (salt ions) (salt ions)

The effect of temperature For most enzymes the optimum temperature is about

30°C Many are a lot lower,

cold water fish will die at 30°C because their enzymes denature

A few bacteria have enzymes that can withstand very high temperatures up to 100°C

Most enzymes however are fully denatured at 70°C

© 2007 Paul Billiet ODWS

The effect of temperature

Temperature / °C

Enzyme activity

0 10 20 30 40 50

Q10 Denaturation

© 2007 Paul Billiet ODWS

The effect of pH Extreme pH levels will produce denaturation The structure of the enzyme is changed The active site is distorted and the substrate

molecules will no longer fit in it At pH values slightly different from the enzyme’s

optimum value, small changes in the charges of the enzyme and it’s substrate molecules will occur

This change in ionisation will affect the binding of the substrate with the active site.

© 2007 Paul Billiet ODWS

Enzymes work in different pH All enzymes can work in different conditions Intestines would have a lower pH than mouth.

Look at website for examples!!!!!!

The effect of pH Optimum pH values

Enzyme activity Trypsin

Pepsin

pH

1 3 5 7 9 11

© 2007 Paul Billiet ODWS

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2. Cofactors and 2. Cofactors and CoenzymesCoenzymes

Inorganic substances Inorganic substances (zinc, iron)(zinc, iron) and vitaminsvitamins (respectively) are sometimes need for proper enzymatic activityenzymatic activity.

Example:Example:IronIron must be present in the

quaternary quaternary structurestructure -- hemoglobinhemoglobin in order for it to pick up oxygen.pick up oxygen.

Inhibitors Inhibitors are chemicals that reduce the rate of

enzymic reactions. The are usually specific and they work at low

concentrations. They block the enzyme but they do not

usually destroy it. Many drugs and poisons are inhibitors of

enzymes in the nervous system. © 2007 Paul Billiet ODWS

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Two examples of Enzyme Two examples of Enzyme InhibitorsInhibitors

a. a. Competitive inhibitorsCompetitive inhibitors:: are chemicals that resembleresemble an enzyme’s normal substrateenzyme’s normal substrate and competecompete with it for the active siteactive site.

Enzyme

Competitive inhibitor

Substrate

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InhibitorsInhibitorsb.b. Noncompetitive inhibitorsNoncompetitive inhibitors::

Inhibitors that do not enter thedo not enter the active siteactive site, but bind tobind to another partanother part of the enzymeenzyme causing the enzymeenzyme to change its shapechange its shape, which in turn

alters the active sitealters the active site.

Enzymeactive site altered

NoncompetitiveInhibitor

Substrate

Metabolic enzymes run all the body organs and systems by performing various chemical reactions within the body cells. Catalase, which breaks down hydrogen peroxide, a metabolic waste product, liberating the oxygen for use in the body..

Metabolic Enzymes

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

Digestive enzymes are secreted by the body to digest the food eaten.

There are three categories of digestive enzymes:

• Amylases (found in saliva, the pancreas, and intestinal juices) break down carbohydrates; • Proteases (found in the stomach, pancreatic, and intestinal juices) help digest protein; • Lipases (pancreatic juices, and in food fats) aid in fat digestion. •

•Amylase enzymes are found in the saliva and in the juices of the pancreas and intestinal tract and help the digestive process by breaking down carbohydrates. There are different kinds of amylase. For example, the enzyme sucrase breaks down the sugar sucrose found in cane and beet sugar. The enzyme lactase breaks down the lactose sugar in milk. The enzyme maltase breaks down the malt sugar maltose.•Protease enzymes are found in the juices of the pancreas, the stomach and the intestinal tract and help with the breakdown and the digestion of proteins.•Lipase enzymes are found in the juices of the stomach and pancreas and help to break down fats.