Download Cellular Respiration

Cellular Respiration
Life is Work
Energy flow
• Energy=one way street
– Sun
– Plants
– Animals
– Heat
• Nutrients=recycled
Catabolic pathways
• Complex molecules=more free energy
• Simple molecules = less free energy
• Spontaneous, exergonic reaction
– Organic compounds+O2 CO2 +H2O+Energy
• Combustion
• Cellular Respiration
ReDox reactions
• Transferring electrons releases energy
• LEO the lion goes GER, OIL RIG
• Na + CL  Na+ + Cl• Oxidized? Reduced?
• CH4 + 2O2  CO2 +2H2O + Energy
– Carbon loses control of electrons, oxygen
gains control of electrons
– Electrons moving toward electronegative
atoms are losing potential energy
Oxidation of Glucose
• C6H12O6 + 6O2  6CO2 + 6H2O + Energy
Sugar is oxidized, oxygen is reduced
– Electrons associated with hydrogen are a
good source of energy as they fall to oxygen
• Carbohydrates
• Fats
• Glucose will burn in air
• Enzymes lower activation energy
Electron Transport Chain
• Releasing all energy is inefficient
• Step-wise degradation harvests more
energy
• Electrons are first passed to NAD+, then
through the electron transport chain, then
to oxygen
NAD+
• Nicotinamide adenine dinucleotide
• Electron acceptor
• Dehydrogenase enzyme removes 2
hydrogens (2 H+, 2 electrons) form sugar
• Gives 2 electrons, 1 H+ to NAD+ NADH
Electron Transport Chain
• Electrons are delivered to ETC by NADH
• ETC breaks the fall of electrons to oxygen
• Each step/transfer releases a
portion of the potential energy
in electrons
Each protein is more electronegative than the
one above it
Electrons move downhill towards oxygen
Food  NADH  ETC Oxygen
Stages of Cellular Respiration
• Glycolysis
• Citric Acid Cycle/ Kreb’s Cycle
• Oxidative Phosphorylation
Glycolysis=Splitting sugar
• Glucose (6C)  2 pyruvic acids (3C)
• Requires energy investment of 2 ATP
• Repays 4 ATP, 2NADH
Energy Investment Phase
• Enzyme transfers 2 phosphates to glucose
– Enzyme that transfers second
phosphate is allosterically regulated by
ATP (shuts down glycolysis when there
is enough ATP in cell)
• 2 Glyceraldehyde -3- phosphate
Energy Payoff Phase
• G-3-P is oxidized by NAD+
• Energy released by this step is used to
attach a phosphate from cytosol
• Phosphate groups are
relocated to ADP by
Enzymes (4 ATP formed)
• Results in 2 pyruvic acid (pyruvate)
Glycolysis Accounting
• Investment = 2ATP
• Payoff = 4 ATP, 2 NADH
• Net return= 2 ATP, 2NADH
• Substrate Level
Phosphorylation