Biology 1002B Lecture Notes - Lecture 7: Pyruvate Dehydrogenase Complex, Citric Acid Cycle, Acetyl-Coa

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8 Feb 2013
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Lecture 7: Energy Transformation II
1. Characteristics of ATP
Energy carrier
2. Role of C-H bond in bioenergetics
Take potential free energy in CH bond and conserve energy into ATP
3. Role of redox potential in bioenergetics
Carriers arranged from more negative to positive redox potential where e- are readily easy to give up
4. Role of FAD, NAD+ as electron carriers
Carry electrons and help create a proton gradient which helps synthesize ATP
5. Location, products, distribution in nature and purpose of pathways such as glycolysis, CA cycle, respiratory
electron transport etc.
Glycolysis
o Cytosol
o Splitting of glucose into 2 molecules of pyruvate
o No carbon is loss
o Oxygen is not needed (anaerobic) since no oxygen present in ancient
anaerobic organisms
o Energy in glucose used to reduce 2NAD+ to 2NADH
Potential energy in 2 pyruvate molecules since some electrons
are loss
o Consume (energy investment) ATP in order to make a net 2 ATP
CA cycle
o Mitochondrial matrix
o Happens twice
o Purpose of cycle: use carbon energy and get rid the rest
of the carbon and free energy transferred to citrate
o Reduce NAD+ to NADH
o Oxaloacetate (4C) + acetyl-coA (2A) 6 carbon citrate
o Oxaloacetate is the substrate of citric acid cycle
6. Role of energy coupling in early steps of glycolysis
Not a spontaneous reaction
o Endergonic reaction coupled with an exergonic reaction
o Exergonic hydrolysis/breakdown of ATP through hexokinase (bind ATP & glucose but not H2O)
Free energy of phosphate conserved by attaching phosphate to glucose
Phosphate group is charged (keep in compartment)
Make glucose more reactive, stable make more ATP
When add up coupled reaction, it is spontaneous
Thermodynamically unstable but kinetically stable (slow, if fast it will heat up cells)
7. Substrate-level Phosphorylation in Glycolysis
PEP + ADP pyruvate kinase pyruvate + ATP
Enzyme catalyzing removing of phosphate
Break CH bonds and conserve that energy into ATP
PEP and gluose-6-phosphate have high phosphoryl transfer potential to make ATP
8. Relative potential energy of various intermediate compounds (eg. glucose vs. pyruvate vs. CO2)
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