Transcript Catabolic Pathways and Glycolysis

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 O2)and
cellular respiration (breakdown with O2).
Redox reactions power the production
of ATP
– Redox Review
• 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
• 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 g A+ + B- (A is the reducing agent, B is the oxidizing agent)
• Xe- + Y g X + Ye- (Xe- is the reducing agent, Y is the oxidizing agent)
Cellular Respiration
• 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)
– C6H12O6 + 6O2 g 6CO2 + H2O + Energy (ATP & Heat) DG = -686 kcal/mol
• this reaction C & H are being oxidized by O2 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)
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Stages of Cellular Respiration
Glycolysis
Citric Acid Cycle
Oxidative Phosphorylation
Glycolysis
• Catabolic process that degrades glucose into 2 Pyruvate molecules + 2 H2O
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 g 2Pyruvate + 4ATP + 2NADH + 2H+
– The left side is called the Energy Investment phase
– The right side is called the Energy Payoff phase
• Complex equation