Enzymes and Chemical Reactions Chapter 4 & 5

Chemical Reactions During a chemical reaction, the atoms in the reactants get rearranged to form products This requires bonds to break and reform… The breaking and forming bonds involve changes in ENERGY!!

Energy in Reactions Breaking bonds absorbs energy from the surroundings, but chemical energy is released Forming bonds releases energy to the surroundings, but chemical energy is stored Chemical reactions either absorb more energy than they release, or vice versa

Energy-Releasing Reactions Often called Exothermic Reactions Often occur spontaneously, or with little activation energy (energy needed to start the reaction)

Energy–Absorbing Reactions Often called Endothermic Reactions Require an energy source

Which is Which??

Enzymes are Catalysts They speed up chemical reactions by lowering the activation energy They speed up reactions in cells at normal body temperatures

Enzyme Structure Enzymes are made up of folded… PROTEIN!! The folds created in the forth level of organization create ACTIVE SITES for SUBSTRATES to bind to An enzyme can only catalyze ONE reaction (lock & key)

How Enzymes Work (Fig 5-13 p.104)

Enzyme Function An enzyme’s structure and shape is critical to its function in the cell High temperatures, changes to the pH, or some environmental factors can DENATURE protein (or unravel it) No folds = No active sites This is why it is important for living things to maintain homeostasis