Chemical Reactions and Enzymes

Energy in Reactions Chemical reactions can release energy or absorb energy. Chemical rxns that release energy often happen spontaneously Chemical rxns that absorb energy usually don’t happen unless there is a source of energy

Examples 2H 2 + O 2  2H 2 O Gives off energy (explosively) 2H 2 O  2H 2 + O 2 (electrolysis – pass electric current through it)

Energy In order to stay alive, organisms need to carry out reactions that require energy Why do you need energy? Grow Grow Breath Breath Think Think Dream Dream everything everything

Activation Energy The energy require to start a reaction is called “Activation Energy”

Enzymes Catalysts – substance that speeds up a reaction by lowering the activation energy Enzymes are proteins that act as biological catalysts Can accelerate a reaction by a factor of – 10 billion times faster! Enzymes are very specific. Usually only one reaction

Naming Enzymes Part of the name of an enzyme usually derived from the reaction it catalyzes Peptinase – helps peptin break down proteins in your small intestines Carbonic anhydrase – catalyzes reaction that removes water from carbonic acid “ase” is usually the suffix of an enzyme

Enzyme Action Reactants must collide with each other with enough energy to break the bonds and form new bonds Enzymes provide a site where the reactants can be brought together to react

Structure The reactants in an enzyme catalyzed reaction are called substrates Each protein has a specific, and complex shape Active site is where the reactants bind to the enzyme The active site and the reactants have complementary shapes – sometimes called “Lock and Key”

Activation Energy Reaction pathway without enzyme Activation energy without enzyme Activation energy with enzyme Reaction pathway with enzyme Reactants Products

Glucose Substrates ATP Substrates bind to enzyme Substrates are converted into products Enzyme-substrate complex Enzyme (hexokinase) ADP Products Glucose-6- phosphate Products are released Section 2-4 Figure 2-21 Enzyme Action Go to Section: Active site

Glucose Substrates ATP Substrates bind to enzyme Substrates are converted into products Enzyme-substrate complex Enzyme (hexokinase) ADP Products Glucose-6- phosphate Products are released Section 2-4 Figure 2-21 Enzyme Action Go to Section: Active site

Glucose Substrates ATP Substrates bind to enzyme Substrates are converted into products Enzyme-substrate complex Enzyme (hexokinase) ADP Products Glucose-6- phosphate Products are released Section 2-4 Figure 2-21 Enzyme Action Go to Section: Active site

Glucose Substrates ATP Substrates bind to enzyme Substrates are converted into products Enzyme-substrate complex Enzyme (hexokinase) ADP Products Glucose-6- phosphate Products are released Section 2-4 Figure 2-21 Enzyme Action Go to Section: Active site

Once done… Once the reaction is complete, the products are released and the enzyme is free to catalyze another reaction There are various methods to control enzyme activity Temperature, pH, and proteins that can turn on or off activity at critical stages