section 2.4 &2.5: enzymes. energy is neither created or destroyed, it continues to be...

Section 2.4 &2.5:

Enzymes

• Energy is neither created or destroyed, it continues to be transferred.

• All Chemical reactions involve a change/transfer in energy.

Chemical Reactions Release and Absorb Energy

Potential Energy Potential to Kinetic Energy

Potential Energy Potential Energy

Observing a Chemical Reaction1. Put 50 mL of water into a flask2. Add 10 drops of Bromothymol Blue (an acid

indicator which will turn the solution yellow if an acid is present)

3. Get the temperature in `C.4. Add one Alka Seltzer tablet (split into two)5. Observe reaction and write down observations6. Get the temperature after the reaction occurs.What you observed was:

CO2 + H2O H2CO3 (Carbonic Acid)

Reactants Product

Energy is needed to start a Chemical Reaction

Activation Energy is the amount of energy that needs to be absorbed to start a chemical reaction– The push to get the bolder to go down the hill

Activation Energy

How can we reduce the amount of activation energy needed to get a reaction started?

2H2O2 2H2O + O2

– This reaction will occur on its own but will take a long time and a lot of activation energy

– Catalysts reduce the amount of activation energy necessary to get a reaction started

– This is a method of cleaning contact lenses using a Manganese dioxide disk which will quickly break hydrogen peroxide into water in oxygen and get your contacts totally disinfected!!• The Manganese dioxide disk can be used over and over again without a

loss of functioning.

A Chemical Reaction with and without a catalyst

• The Catalyst decreased the amount of activation energy needed to get the reaction started

a catalyst

a catalyst

Does anyone suffer from eating…? …Beans, peanuts, broccoli, cauliflower, brussel

sprouts, cabbage, peppers, onions…?• You know what I am talking about!!!

• This happens because we can’t digest alpha-galactosidose present in these foods • There is something to prevent this!! • Beano contains the enzyme alpha-galactosidase

to allow us to break down alpha-galactosidose

Maybe you can’t tolerate lactose sugar and are lactose intolerant.

What do people do who are lactose intolerant?They take Lactaid pills which contain the enzyme

Lactase

Enzymes are protein catalysts made by living organisms that reduce the amount of activation energy necessary to start and control the rate of a chemical reaction

Our cells always produce Hydrogen Peroxide.2H2O2 2H2O + O2

This is highly toxic to our cells.An enzyme called catalase will allow hydrogen

peroxide to quickly break down to water and oxygen.

One catalase molecule can convert millions of molecules of hydrogen peroxide to water and oxygen each second

Characteristics of Enzymes

1. Made up of Proteins2. Are specific to whatever they act upon3. Are reusable – don’t get used up in a

chemical reaction4. Usually have names ending in “ase”5. Enter directly into a reaction

How Enzymes work• Their shape is specific to what they act upon

(the substrate)• They will bind directly to the substrate as an

enzyme-substrate complex• The binding site is called the Active Site• A substrate and its enzyme fit together like

puzzle pieces – Lock and Key Theory

What can influence an enzymes reactivity?1. Temperature

Since enzymes are proteins, their structure can be changed or destroyed by high temperatures.

As temperature increases, the rate of enzyme activity increases to a point then quickly decreases.

In us, this temperature is at ~ 40`C

2. pHToo high or too low pHs will effect the enzyme activity and possibly change its shape.Different for different organs

3. Concentration of enzymes As the number of enzymes increases, the rate of

reaction increases also to a point where all the enzymes are already bound to an active site of a substrate.

Additional enzymes won’t speed up a reaction at this point.