reactants and products a chemical reaction is the process by which atoms or groups of atoms in...
TRANSCRIPT
Reactants and Products A chemical reaction is the
process by which atoms or groups of atoms in substances are reorganized into different substances bonds are formed or broken.
Clues that a chemical reaction has taken place include the production of heat or light, and formation of a gas, liquid, or solid (a new substance).
Chemical Reactions
Chemical reaction
Physical change
Chemical Equations
Chemical formulas describe the substances in the reaction and arrows indicate the process of change.
Reactants are the starting substances, on the left side of the arrow.
Products are the substances formed during the reaction, on the right side of the arrow.
This equation shows cellular respiration -- a series of chemical reactions that require glucose and oxygen as reactants.
Glucose sugar molecules are broken down and the energy from its covalent bonds is released.
Carbon dioxide and water are produced. In a chemical reaction, the atoms in the reactants are rearranged
to form new compounds (products).
A Chemical Equation
Glucosefrom food
Oxygen from air
Carbon dioxide
Water
REACTANTS PRODUCTS
+ ENERGY
Balanced Equations
The law of conservation of mass states matter cannot be created or destroyed.
The number of atoms of each element on the reactant side must equal the number of atoms of the same element on the product side.
Chemical Reactions
This equation is balanced.
Energy is needed to form covalent bonds. Breaking covalent bonds releases energy.
The activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction.
Energy of Reactions
Chemical Reactions
ZA+B
AB
This reaction is exergonic and released heat energy (exothermic).Ex.: hand warm packs, metabolic reactions that warm up the body
The energy of the product is lower than the energy of the reactants.
Chemical Reactions
ZA+B
AB
This reaction is endergonic and absorbed heat energy (endothermic).Ex.: “ice” packs used in sports injuries
The energy of the products is higher than the energy of the reactants.
Chemical Reactions
A+B
AB
A catalyst is a substance that lowers the activation energy needed to start a chemical reaction.
• It does not increase how much product is made and it does not get used up in the reaction.
• Enzymes are biological catalysts; they are proteins.
EnzymesChemical Reactions & Enzymes
A+B
AB
The reactants that bind to the enzyme are called substrates; enzymes are specific for their substrates/reactions.
The specific location where a substrate binds on an enzyme is called the active site.
Chemical Reactions & Enzymes
What determines the specificity of an enzyme?
Chemical Reactions & Enzymes
The active site changes shape and forms the enzyme-substrate complex, which helps chemical bonds in the reactants to be broken and new bonds to form.
Factors such as pH, temperature, and other substances affect enzyme activity.
All the chemical reactions happening inside an organism make up its metabolism enzymes control metabolic reactions
Two Models of Enzyme Function
Lock & Key – the enzyme’s active site has a shape that is specific for the substrate; the substrate “fits” like a key into the active site
Induced Fit – as the substrate binds, the enzyme changes shape and the active site conforms to the substrate
Metabolic Reactions Anabolic reactions = building up organic molecules; usually
endergonic
Ex.: Synthesis / Condensation – putting together building blocks to make a larger molecule
Catabolic reactions = taking apart organic molecules; usually exergonic
Ex.: Digestion, breaking down proteins and other large molecules
Which arrow represents an anabolic reaction? Catabolic reaction?
Link to Virtual Lab – Effect of Substrate Concentration and pH on Enzyme Activity:
http://glencoe.mcgraw-hill.com/sites/dl/free/0078759864/383930/BL_11.html