BiologyChemical Reactions
Definitions for Section 8•Chemical reaction•Reactant•Product•Activation energy•Catalyst•Enzyme•Substrate•Active site
•pH•Acid•Base
Reactions• CHEMICAL REACTION:
Process by which atoms or groups of atoms in subs are reorganized into different subs
• Rust (Fe2O3) is formed when iron reacts and combines with oxygen▫ A chemical change has
occurred
•Chem reactions have several parts:▫REACTANTS: The starting substances; left side of
arrow▫PRODUCTS: Subs formed during the reaction; right
side of arrow▫Arrow means “yields”▫Reactants Products▫Example:
6CO2 + 6H2O + energy from sun C6H12O6 + 6O2
Energy and Reactions•What do you need to bake a
cake?•After ingredients are mixed,
energy must be applied•ACTIVATION ENERGY: The
minimum amount of energy needed for reactants to form products▫Ex. Flame applied to candle
provides enough energy to begin reaction
▫This type of reaction called exergonic Releases energy Products have less
energy than reactants
Examples: animals breaking down food, burning a candle
▫This is an example of an endergonic reaction Requires high
amount of energy to form products
Products have more energy than reactants
These reactions STORE ENERGY
Example: photosynthesis, making a candle
Kick It Up a Notch
•Most chem reactions happen slowly (high act. energy)
•CATALYST: Substance that lowers the activation energy needed to start a chemical reaction
• In biological reactions, our catalyst is an ENZYME▫ ENZYME: Special protein that speeds up a chem reaction▫ “All enzymes are proteins but not all proteins are enzymes”▫ Can be identified with the ending “ase”
Examples: sucrase, DNA polymerase, lactase▫ Enzymes also break things down and synthesize things▫ Never “used up” in reactions ▫ SUBSTRATE: The thing that binds to the enzyme
• ACTIVE SITE: The specific area that a substrate connects to on the enzyme▫ Shape of active site very specific to substrate and enzyme
Called Lock-and-key mechanism• Enzymes work best when factors such as pH, temp, and
salinity are in certain range▫ DENATURATION: Breakdown of a protein into an
unusable state
Active sites
More Chemistry• pH has an effect on
enzyme activity▫pH: measurement of the
ACIDIC or BASIC a solution is
▫Scale of 0-14• ACIDS: Chemicals that
produce hydrogen ions (H+); have pH from 0-7▫Taste sour▫Corrosive to metals▫Turn litmus paper pink▫Examples: citric, stomach,
vinegar
•BASES: Substances that have a pH from 7-14▫Feel soapy or slimy▫Strong bases can be
corrosive to organic matter
▫Turn litmus paper blue▫Examples: ammonia,
sodium hydroxide (lye)
•The pH scale measures from 0-14•Acids (0-7)•Bases (7-14)•Strongest acids have lowest pH, strongest
bases highest•Water is neutral (pH of 7)
Section 5 Assignment• Identify the reactants and products:
▫AB + CD AD + BC• What is the purpose of a catalyst?• Why is no further energy required when a
candle wick is ignited?• Draw a Venn diagram for exergonic and
endergonic reactions. • When fevers hit 106 Farenheit, it’s time to call
the doctor. Learning what you just did about proteins, why is that a bad thing?
• Draw and label an enzyme that you create, the substrate that it will break down into products, and the active site. Do NOT use a picture from your book or notes. CREATE YOUR OWN!!
Section 5 Assignment• Identify the reactants and products:
▫AB + CD AD + BC• What is the purpose of a catalyst?• Why is no further energy required when a
candle wick is ignited?• Draw a Venn diagram for exergonic and
endergonic reactions. • When fevers hit 106 Farenheit, it’s time to call
the doctor. Learning what you just did about proteins, why is that a bad thing?
• Draw and label an enzyme that you create, the substrate that it will break down into products, and the active site. Do NOT use a picture from your book or notes. CREATE YOUR OWN!!
Active sites
Lock-and-Key Mechanism of
Enzymes
The pH Scale