Catabolic Pathways and Glycolysis The ability to do that work depends on catabolic process that harvest the potential energy found in organic molecules. The 2 catabolic processes that occur in organisms are: – fermentation (breakdown without O 2 ) – cellular respiration (breakdown with O 2 ).

Redox reactions power the production of ATP Redox Reactions power the production of energy within the cell.

Reduction Reactions Reduction - the gain of negative charge on an atom as it becomes more negative – can occur through transfer of an e - or through unequal sharing of the e - – the atom or molecule that donates the charge is the reducing agent – atoms rich in H make great reducing agents because they are the least electronegative and are oxidized easily - called "hilltop" electrons NAD + + 2H  NADH + H + 2e - gained by NADH to be used in a later reaction H + to be used to establish an ion gradient within the mitochondria

Oxidation Reactions Oxidation - the loss of negative charge on an atom as it becomes more positive – can occur through the loss of an e - or the movement of an e - away from the atom – the atom or molecule that accepts the charge is the oxidizing agent A + B  A + + B - (A is the reducing agent, B is the oxidizing agent) Xe - + Y  X + Ye - (Xe - is the reducing agent, Y is the oxidizing agent)

Cellular Respiration Stages of Cellular Respiration Glycolysis Citric Acid Cycle Oxidative Phosphorylation primary catabolic pathway used in organisms to produce energy (ATP) – although fats & proteins can be broken down, glucose is the primary fuel used – energy gained is through the transfer or relocation of electrons throughout the process (redox)

Cellular Respiration C 6 H 12 O 6 + 6O 2  6CO 2 + H 2 O + Energy (ATP & Heat)  G = -686 kcal/mol – this reaction C & H are being oxidized by O 2 to yield the energy for the production of ATP NAD + is an oxidizing agent in cellular respiration as is accepts a H atom & becomes NADH + H + (the enzyme dehydrogenase removes 2 e - to energize the NADH complex) the energy stored in the bonds is later used to create ATP (& water as oxygen accepts the used H)

Glycolysis Catabolic process that degrades glucose into 2 Pyruvate molecules + 2 H 2 O molecules – occurs in the cytosol – requires the input of 2 ATP molecules and produces 4 ATPs (net of 2) – 2 NAD + are reduced to 2 NADH + 2 H + (net gain of 4e - ) Pyruvate is then transported into the mitochondria to begin the Citric Acid Cycle Reaction does not require oxygen (anaerobic process) – No CO2 is produced! – All C atoms are present in the final products of the reactions Simplified equation – Glucose + 2ATP + 2NAD  2Pyruvate + 4ATP + 2NADH + 2H + – The left side is called the Energy Investment phase – The right side is called the Energy Payoff phase Complex equation