Chemical reactions and enzymes2.4

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 overSucrase 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)