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