Kin 217 – October 31st
- Midterm 1 – Review
- See Eric Rm 3041 (2-5pm – Tues)
- Ken Stark Thursday 1-4pm
- The electron transport chain
o NADH + H+ + ½ O2 NAD+ + H2O
∆Go’ = -220 kJ mol-1
End going of ETC is eventually to get down to water
o Reaction X- + Y X + Y-
Can be written as two half reactions:
X- X + e- (redox couple)
Y + e- Y- (redox couple)
- Redox Couple
o Redox potential value
Electron affinity or electron donating capacity
Given in volts, voltmeter to measure electron flow
o Tend to need a pair of redox (for reaction to occur, you need a pair!)
One donator (more negative)
One receiver
(In previous slide, donator is X, receiver is Y…)
- Determination of redox potentials
o Eo’
Relate to all components at
1 M concentration
Hydrogen gas at 1 atmosphere pressure
pH 7.0
Similar between redo potential and standard free energy…
o There is a simple relationship between Gibs free energy change and redox
potential difference
∆Go’ = -nF∆Eo’
N = number of electrons
F = Faraday’s constant (96.5 kJ V-1 mol-1)
- Electrons are transported in a stepwise fashion
o Free energy change
Series of steps involving a number of carriers
Called oxidative phosphorylation
(NAD higher on the staircase than FAD)
At each stage there’s a potential to capture energy into ATP
- Fig 11.7
o Starting with NADH, it moves down staircase, releasing free energy,
gaining ATP (?)
- Fig 11.8
o Puts everything together in ch 11
- Energy release from oxidation of other fuels
o Fatty acids and glucose
Feed into the citric acid cycle via acetyl CoA
16 carbon can get 8 pyruvate (?)
o Amino Acids
Converted to pyruvate, acetyl CoA or to citric acid cycle
intermediates
Gluconegenesis…those AA that can form pyruvate can form
- Fig 11.10
o Once you convert to Acetyl CoA there’s no turning back…can’t go back
to pyruvate from Acetyl CoA
- The interconvertibility of fuels (Fig 11.11)
o Thus, when you have Acetyl CoA, you can get the synthesis of fatty acids
OR it can go into the citric acid cycle (2 possibilities)
- Chapter 12
- Glucose or glycogen? (Fig 12.1)
o Glucose-6-phosphate really is a trap to enter glycolysis…key starter
material
- Why use ATP here at the beginning of glycolysis?
o Glycolysis involves phosphorylated compounds
o Phosphate groups are key to move around and shift energy…
o For phosphorylation to be irreversible
ATP must be used, which costs a high energy phosphate
Traps glucose
- Fig 12.7
o First step is to form Fructose-6-phosphate
o Why bother doing this step??
- Why is glucose-6-phosphate converted to fructose-6-phosphate?
o Want to split a C6 compound to two C3 compounds (this is where
knowing your structures and organic chem. comes in handy! =S)
o Fructose-6-phosphate
Favours a reverse aldol condensation
- Fig 12.4, 12.5
o Aldehyde to ketone formation (?)
o Ketones allows the bond beside it to break
- Splitting fructose bisphosphate to two C3 compounds
o ∆Go’ o aldolase is 23.8 kJ mol-1
Energetically unfavourable
o BUT
∆G = ∆Go’ + RT ln [products]/[reactants]
(taken from chapter 3! Review it!)
- A note on the ∆Go’ and ∆G values for the aldolase reaction
o ∆Go’ values
1 M concentrations giving +23.8 kJ mol-1
o ∆G at the cellular concentrations
1000x lower
Products present as a square term
F-1:6-bP is linear term,
o Actual ∆G value is much closer to zero
-1.3 kJ mol-1
Standard free energy isn’t necessarily the same as free energy
- Referring back to the fig 12.4 (?)
o Isomers that are interconverted
o In equilibrium
o Removal of glyceraldehyde-3-phosphate
- Fig 12.6
o Highlight the top…
o Glyceraldehyde acts to reduce NAD…
- Glyceraldehyde-3-phosphate dehydrogenase
o Condensation
Glyceraldehyde-3-phosphate and a cysteine SH group of the
dehydrogenase
o Transfers electrons to NAD+
Formation of a thioester
o Thioester reacts with Pi to form a high energy phosphate
Aldehyde reaction with SH group…
- Fig 12.6
o We finally MAKE some ATP
o Thioester step to get high NRG substrate
- Glyceraldehyde-3-phosphate dehydrogenase
o High energy phosphate on substrate transferred to ADP to form ATP
Substrate-level phosphorylation
- The final steps of glycolysis
o Phosphoglycerate has low energy phosphate ester
o Shift from 3 position to 2 position…(3-phosphoglycerate to 2-
phosphoglycerate)
This allows it to form ATP
- Fig 12.7
o Enzymes in red Irreversible reactions
o 2 ATP required per glucose (to get glucose to glucose-6-phosphate, one to
form glucose bisphosphate (?)—check this…)
o 4 ATP generated per glucose
o 2 ATP net gain per glucose