Energy and Reactions Honors Biology

Energy Energy – ability to do work or cause a change Kinetic Energy  energy of motion Ex: Heat, moving ball Potential Energy  stored energy as a result of position or location Ex: Sitting ball ATP – adenosine triphosphate Unit of energy cells use 3 phosphates; 3rd P has high energy bond

ATP Adenine Triphosphate Ribose

Chemical Reactions Bonds between atoms are made or broken and the substances change into something else Represented by chemical equations Ex: Methane burning in air CH4 + 2O2 → CO2 + 2H2O (reactants) (products) Equation must be balanced (coefficient vs. subscript)… PRACTICE!!! Atoms are never created or destroyed, only change form

PRACTICE PROBLEMS 1) ____ H2 + ____ O2  ____ H2O 2) __ AlBr3 + __ Cl2  __ AlCl3 + Br2 **3) __Ca(OH)2 + __H3PO4  __ Ca3(PO4)2 + __H2O

Answers WRONG: 4AlBr3 + 6 Cl2  4 AlCl3 + 6 Br2

Answers 1) 2 H2 + 1 O2  2 H2O 2) 2 AlBr3 + 3 Cl2  2 AlCl3 + 3 Br2 **3) 3 Ca(OH)2 + 2 H3PO4  1 Ca3(PO4)2 + 6 H2O

Endergonic Reactions – absorbs energy Energy absorbed from surroundings and stored in bonds Ex: Photosynthesis Products have more ENERGY than reactants Exergonic Reactions – releases energy Releases ENERGY to environment Ex: Cellular Respiration Reactants have more ENERGY than products Energy Coupling – Energy released from exergonic rxns powers endergonic ones

Real Life Examples… Exergonic (Exothermic) Cellular Respiration Energy (ATP) is released when glucose is broken down Endergonic (Endothermic) Photosynthesis Energy (ATP) is NEEDED (consumed) to put together glucose from CO2, H20 and sunlight