Chemical reactions and enzymes 2.4

Chemical reactions Change one substance into another Involve changes to the chemical bonds that hold molecules together

Energy in reactions Reactions that release E can happen spontaneously Reactions that absorb E can’t happen without an energy source (ex: the sun for photosynthesis)

Activation energy The energy needed to get a reaction started.

Enzymes Lower the activation energy Act as a catalyst Not used up in the reaction Speed up chemical reactions that take place in cells

How enzymes work The shape of the enzymes allow substrates (reactants) to bind to it While bound to the enzyme, the substrates react When the products are released, the enzyme is free to start the process over Sucrase breaks apart sucrose

Enzymes Can make a reaction go 10 million times faster! Are very specific – only catalyze one reaction each Are affected by pH and temperature Are essential for life processes

Restriction enzyme binds to DNA (blue) Enzyme from an Insect-eating plant

Human salivary amylase (spit)