6.2 enzymes and chemical reactions pages 156-160
TRANSCRIPT
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6.2 Enzymes and Chemical
Reactionspages 156-160
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• Chemical reactions take place all the time.• Chemical reactions change substances
into different ones by breaking and forming chemical bonds.
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• 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:
6CO2 +6H2O+light energyC6H12O6 + 6O2
Reactants
Products
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• 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.
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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 known as enzymes, which serve as catalysts.
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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.
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Characteristics of Enzymes
1. Enzymes are proteins
2. Enzymes are reusable!
3. Enzymes denature in high temperatures* denature = destroyed, broken apart, digested* denaturation is not reversible
4. All enzymes end with ‘ase’. Ex) Lactase breaks down Lactose (milk sugar)
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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 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*
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‘Lock and Key Model’ – says there is a perfect fit between
active site and substrate
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VOCABULARY
• Enzymes – biological catalysts or special proteins that speed up chemical reactions
• Catalysts – substances that speed up chemical reactions)
• Substrates – materials that bind to the enzyme
• Active Site - Location on the enzyme where the substrate binds
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An Enzyme at WorkReactant
ProductsEnzyme-SubstrateComplex
Active site
Unchanged enzyme
Substrate
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How an enzyme affects a chemical reation:
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How do enzymes speed up reactions?
• Enzymes lower the activation energy of a reaction:
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Factors that Affect Enzyme Activity
1. TEMPERATURE- Too warm, enzyme will denature.- Too cold, enzymatic activity will slow down.
2. pH
- a change in pH can change the shape of the enzyme so that substrates can’t fit into active site.
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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
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• If you did not complete lab. Do that FIRST!• Enzyme worksheet• Pg 160 1 and 4• Pg 175-176: 1,2,4,7,14-23