Chemical Reactions and Enzymes Standard 1.3

Chemical Reactions Changing one set of chemicals into different chemicals. Configuration of elements in molecule or compound is changed, not the kind of elements Many chemical reactions require energy to occur. Some chemical reactions release energy.

Chemical Reactions Reactants- the molecules or compound that are changed in a reaction. Products- the resulting new molecules or compounds Reactants  Products Yield (shows the direction of the reaction) 2H2 + O2  2H2O Reactants Products

Learning Check In the following chemical reaction, which set of chemicals are the reactants? C6H12O6 + O2  CO2 + H2O C6H12O6 + O2

Activation Energy Activation Energy The amount of energy needed to start a chemical reaction Catalyst Lowers the activation energy of a reaction, speeding up the rate of the reaction

Learning Check What is activation energy? The energy needed to stop a reaction. The energy needed to start a reaction.

Enzymes Enzymes are catalytic proteins: (proteins that act as catalysts) change the rate of reactions in living things without being consumed (used). Activation Energy (EA) is lowered causing the reaction to happen faster

Learning Check When activation energy is lowered the rate of the reaction Stops Increases Slows down Stays the same

Enzyme-substrate complex Substrate- the reactants of a chemical reaction that uses an enzyme to occur Active site: pocket or groove on enzyme that binds to substrate

Enzyme-substrate complex Substrates are converted to products Enzyme remains unchanged and is released to find more substrates

Learning Check What happens to an enzyme after it catalyzes a reaction? It is broken down It is unchanged and finds more substrate It becomes part of the product Nothing

Enzyme Action Highly specific- one enzyme for each substrate or set of substrates Substrates bind to the active site of the enzyme where the reaction occurs

Lock and Key Just like there is only one key shape for each lock, there is only one type of enzyme for each type of substrate. Substrate Active Site Enzyme

Enzyme Action

Learning Check What does it mean that enzymes are “highly specific?” A. There is only one kind of enzyme for each kind of substrate.

Regulating Enzyme Activity Enzymes depend on certain conditions to work Homeostasis- all have optimum (best) temperature and pH.

Proteins (enzymes) will be denatured if conditions are not perfect and will stop working.

Learning Check What kind of conditions would cause an enzyme to denature and stop working? pH too high pH too low temperature too high All of the above

Inhibitors Some enzymes are inhibited by competitors (look and act like substrates without reacting). Keeps enzyme catalyzed reactions under control

Some enzymes must be activated by another protein before they can bind to their substrates Activator Substrate

Naming Enzymes 1. Enzymes are named for the reaction the catalyze. Lactase is the enzyme that helps break down lactose. 2. -ase: Almost all enzymes end in the suffix –ase Examples: Amylase, DNA polymerase, catalase

Learning Check When naming enzymes, what three letters are usually used as a suffix? -ose -ase -aes -yme

Summary Many chemical reactions require energy to occur. This is called activation energy. Enzymes are proteins that lower the activation energy of a reaction, make the reaction happen faster. Enzyme are highly specific, working only with certain substrates, and working only at optimum conditions.