6.2 Enzymes and Chemical Reactions pages

Chemical reactions take place all the time. Chemical reactions change substances into different ones by breaking and forming chemical bonds.

Reactants are the starting materials. The newly formed substances are called products, which are different from the reactants. Reactants on the left, Products on right. For example: 6CO 2 +6H 2 O+light energy  C 6 H 12 O 6 + 6O 2 Reactants Products

The key to starting a chemical reaction is energy. Activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction.

Enzymes in Chemical Reactions Sometimes, the energy required for a reaction to take place is too high. The reaction can’t take place unless additional substances are present to reduce the activation energy. These substance are proteins known as enzymes, which serve as catalysts.

Catalysts are substances that speed up chemical reactions by decreasing activation energy. A catalyst lowers activation energy Enzymes are catalysts Most reactions would occur too slowly without the help of enzymes, which speed up chemical reactions.

Click HERE to learn more about enzymesHERE ENZYMES _____ like a _______________ to only _________of _________. Enzymes are ___________ by the reaction and ___________ LOCK AND KEY REUSABLE UNCHANGED FIT ONE KIND SUBSTRATE

Substrates bind to an enzyme at certain places called active sites. The enzyme brings substrates together and weakens their bonds. The catalyzed reaction forms a product that is released from the enzyme. -Substrates are brought together. -They attach to the active site of enzymes. - Bonds are then made or broken. - Product is released. The lock-and-key model helps illustrate how enzymes function. Enzymes are SPECIFIC (they break down only one thing) *They will only FIT with certain substrates*

Another way to look at it… substrate (sucrose)enzyme (sucrase)  substrate (sucrose) + enzyme (sucrase)  enzyme-substrate complex  and+ sucrase glucosefructose glucose fructose products +enzyme

An Enzyme at Work Reactant Products Enzyme-Substrate Complex Active site Unchanged enzyme Substrate hill.com/sites/ /student_view0/c hapter2/animation__how_enzymes_work.h tml

How an enzyme affects a chemical reation: Free Energy Progress of the reaction Reactants Products Free energy of activation Without Enzyme With Enzyme

How do enzymes speed up reactions? Enzymes lower the activation energy of a reaction:

What Affects Enzyme Activity? Two factors:Two factors: 1.Environmental Conditions 2.Enzyme Inhibitors PS. There are actually more but we wont talk about those PS. There are actually more but we wont talk about those

1. Environmental Conditions Enzymatic reactions environmental conditionsEnzymatic reactions are very specific. The following environmental conditions affect enzymatic reactions: 1.Temperature (extremes most dangerous): - high temps denature enzyme. - high temps may denature the enzyme. 2.pH (most like pH - neutral) 3.Ionic concentration (salt ions)

Conditions that are TOO ACIDIC or TOO HOT cause proteins to ________ or _________ pH temperature UNWIND DENATURE See a movie Choose narrated

Denaturing _______ the _______ of the ______________ so enzyme ______________ to ____________ Image modified from: _______________ (keeping pH and temperature constant) is ______________ for maintaining ____________________ HOMEOSTASIS changesshape ACTIVE SITE CAN’T BIND SUBSTRATE IMPORTANT ENZYME FUNCTION

2. Enzyme Inhibitors Two examples:Two examples: a.Competitive inhibitors: resembleenzyme’s normal substrate competeactive site a.Competitive inhibitors: are chemicals that resemble an enzyme’s normal substrate and compete with it for the active site. Enzyme Competitive inhibitor Substrate

2. Enzyme Inhibitors b.Noncompetitive inhibitors: do not enter the active site bind to another part enzyme enzymechange its shape alters the active site Inhibitors that do not enter the active site, but bind to another part of the enzyme causing the enzyme to change its shape, which in turn alters the active site. Substrate Enzyme active site altered Noncompetitive Inhibitor

Many enzyme NAMES end in _____ and the beginning of the name tells what it does DNA Polymerase= “polymerizes” joins monomers to make DNA Protease= breaks down proteins ATP synthase= synthesizes ATP -ASE

3. What is the optimum temperature for the enzyme? 4. At what temperature is the enzyme completely denatured? 1. What is this graph showing? 2. What is the independent variable? 62°C 40°C temperature and enzyme activity temperature