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Aerobic Respiration Summary
Glycolysis Glucose + 2ADP + 2Pi + 2NAD+ à 2 pyruvate + 2ATP + 2NADH + 2H+
Pyruvate Oxidation 2 pyruvate + 2NAD+ + 2CoA à 2 acetyl-CoA + 2NADH + 2H+ + 2CO2
Citric Acid Cycle/Krebs Cycle 2 acetyl-CoA + 6NAD+ + 2FAD + 2ADP + 2Pi à 4 CO2 + 6NADH + 6H+ + 2FADH2 + 2 ATP + 2CoA
Electron Transport Chain (ETC) ---
Aerobic Respiration Summary
¨ Most of the potential energy from glucose is transferred to high-energy molecules, NADH and FADH2
Cellular Respiration Energy Molecules Produced
Glycolysis 2 ATP 2 NADH
Pyruvate Oxidation 2 NADH
Krebs Cycle 2 ATP 6 NADH 2 FADH2
Two Methods of ATP Synthesis
¨ Substrate‐level phosphorylation ¤ direct ATP formation through phosphate transfer from
substrate to ADP ¤ Occurs in glycolysis & Kreb cycle
¨ Oxidative phosphorylation ¤ indirect ATP formation through redox reactions involving
O2 as a final electron acceptor ¤ Driven by the electron transport chain
Substrate-level Phosphorylation
¨ Formation of ATP by direct transfer of phosphate group from a substrate to ADP
Oxidative Phosphorylation
Involves 2 processes that occur on the inner mitochondrial membrane (IMM): ¨ Electron Transport Chain:
¤ Energy in electrons of NADH and FADH2 used to drive H+ against its concentration gradient
¤ Electrons fall to oxygen (final electron acceptor)
¨ Chemiosmosis: ¤ Using facilitated diffusion of H+ to drive the synthesis of
ATP
Electron Transport Chain Overview
¨ Occur on the inner mitochondrial membrane ¨ The ETC extracts energy stored in the NADH and
FADH2 molecules and covert it to ATP by: ¤ Move protons against its concentration gradient
creating a proton gradient across the inner mitochondrial membrane (IMM)
¤ Final electron acceptor is oxygen which converts H2O
¨ All reactions are redox reactions
ETC: Complex I
¨ 2 e‐ from NADH are transferred to Complex I
¨ Protons are pumped across the
inner mitochondrial membrane (IMM) by Complex I
ETC: Ubiquinone (Q)
¨ e‐ are transferred from Complex I to ubiquinone (Q)
¨ Q is lipid soluble (hydrophobic molecule)
¨ can move within the phospholipid bilayer
¨ mobile component within the IMM
¨ It shuttles e- from complex I to complex III
ETC: Complex III
¨ e‐ are transferred from Q to Complex III
¨ Protons are pumped across the IMM by Complex III
ETC: Cyt C
¨ e‐ are transferred from Complex III to cytochrome c (cyt c)
¨ cyt c is a mobile component on the surface of IMM (peripheral)
¨ in the intermembrane space ¨ It shuttles e- from complex III
to complex IV
ETC: O2
¨ O2 is the final electron acceptor of the ETC
¨ enough e‐ pass through the ETC to produce full H2O molecules
¨ Protons are pumped across
the IMM by Complex IV
ETC Components: Complex II
¨ 2e‐ are transferred from FADH2 to Complex II
¨ no protons are pumped across
the IMM
¨ e‐ are transferred from Complex II to Q and proceed through the rest of ETC
Driving Force Behind Electron Transport
¨ Each electron transfer step is energetically favorable
¨ Each carrier in the chain has a higher electronegativity than the carrier before it
¨ Electrons from NADH and FADH2 lose energy (pulled downhill) by each electron carrier to pump H+
Driving Force Behind Electron Transport
¨ Final electron acceptor is the very electronegative oxygen
¨ Oxygen drives the entire process of ETC
¨ Lack of oxygen prevents this whole process from occurring
Proton Motive Force: Chemiosmosis
¨ The electrochemical gradient produced by the ETC: ¤ High proton concentration in the intermembrane space
¨ Chemiosmosis: facilitated diffusion of proton down the concentration gradient (Passive) ¤ Occurs by coupling passive movement of protons to
produce ATP through the enzyme complex ATP synthase ¤ ATP is produced as protons flow through ATP synthase
ATP Synthase
¨ Fo = rotor ¤ Transmembrane ¤ Proton channel
¨ F1 = knob, rod ¤ Peripheral ¤ catalytic sites that
phosphorylate ADP to ATP
ATPase: http://www.youtube.com/watch?v=PjdPTY1wHdQ&feature=related
Links
ETC ¨ http://highered.mcgraw-hill.com/sites/0072507470/
student_view0/chapter25/animation__electron_transport_system_and_atp_synthesis__quiz_1_.html
¨ http://www.youtube.com/watch?v=lRlTBRPv6xM&feature=related
Proton gradient ¨ http://www.youtube.com/watch?v=3y1dO4nNaKY&
%20feature=related
ATP Production
¨ In general: ¤ 1 NADHà3 ATP molecules ¤ 1 FADH2à2 ATP molecules ¤ The ETC is coupled with ATPsynthesis.
ATP Production Summary
¨ Most of the potential energy from glucose is transferred to high-energy molecules, NADH and FADH2
Cellular Respiration Energy Molecules Produced
Glycolysis 2 ATP 2 NADH
2 ATP 4-6 ATP
Pyruvate Oxidation 2 NADH
6 ATP
Krebs Cycle 2 ATP 6 NADH 2 FADH2
2 ATP 18 ATP 4 ATP
Total 36-38 ATP
Question 1
¨ The electrons that are transferred through the electron transport system initially belonged to: A) NADH B) FADH2 C) ATP D) oxygen E) NADH and FADH2
Question 2
¨ The movement of protons through ATP synthase occurs from the A) matrix to the intermembrane space. B) matrix to the cytoplasm. C) intermembrane space to the matrix. D) intermembrane space to the cytoplasm. E) cytoplasm to the intermembrane space
Question 4
¨ The formation of ATP as a result of the activity of the electron transport system is termed substrate-level phosphorylation. A) True B) False
Question 5
¨ The function of the enzyme ATP synthase is to... A) accept a proton from inside the cell membrane as it
accepts electrons B) utilize the energy of the proton motive force to
convert ADP to ATP C) produce reduced coenzymes like NADH D) transfer hydrogen to the electron transport chain E) shuttle electrons from NADH to a terminal electron
acceptor
Question 6
¨ When protons are pumped outside the cell membrane A) water is made B) a proton motive force is created C) NADH gets reduced D) electrons are lost