Oxidative Phosphorylation Flashcards
How is energy from the ETC used?
Energy from the electron transfer/proton pumping converted into high phosphoryl transfer potential energy
________ and ________ occur together
Electron flow and proton pumping
Flow of electrons from NADH to O2 is a __________ reaction
Exergonic
1 NADH = ______ ATP
2.5 ATP
1 FADH2 = ______ ATP
1.5 ATP
No proton pumping occurs in ______
Complex II
Mitchell’s Chemiosmotic Hypothesis
There is a proton gradient across the inner mitochondrial membrane and it could be used to drive ATP synthesis
2 components of the gradient
Creates?
- Chemical (pH) gradient
- Electrical gradient (charges)
Create an ELECTROCHEMICAL gradient
Matrix pH vs. intermembrane space pH
Matrix pH = 8.0
Intermembrane space pH = 6.0
_________ drives the protonation / deprotonation of the _________ residues on the _____________
The chemical (pH) gradient
Aspartic acid
C subunits
Inner mitochondrial leaflet facing matrix is _______ charge
Negative
Inner mitochondrial leaflet facing outer membrane is ______ charge
Positive
Electrochemical potential
Potential energy driving H+ to return to the matrix
Complexes pump protons into the ___________ creating _________
Protons are pumped into the intermembrane space creating the proton motive force
As proton flow back into the _______ through ________, the ______ drive the synthesis and dissociation of ________
Matrix
ATP synthase
Proton motive force
ATP
F0 domain of ATP synthase
structure and location
- Located in the inner membrane
- Made up of individual C subunits
- “A” region is the pore consisting of 2 half channels
Proton flow through the F0 region of ATP synthase
Proton from IMS enters —> protonates aspartic acid side chain (COO- becomes protonated) on C subunit —> C subunit advanced until you get another C subunit and another proton entering through half channel —> entire C ring rotates until every subunit is protonated —> whatever C subunit is lined up with the matrix half channel, proton goes through and returns to the matrix —> COO- is restored
What amino acid undergoes protonation/deprotonation in the C subunits?
Aspartic acid
COO- group
F1 domain of ATP synthase
Important subunits (4)?
Gamma
Beta
Alpha
B2
Gamma subunit of F1 domain
Function and importance
Serves like a rotor
As C ring turns based on movement of protons, the gamma subunit rotates and drives different conformational changes in the alpha and beta subunits
Importance: Connects movement of C ring with the conformational changes of alpha and beta subunits
Alpha subunit of F1 domain
Importance and function?
NO role in ATP synthesis
Importance: To F1 domain structure and function…conformational changes
Beta subunit of F1 domain
Function
Synthesis and release of ATP
B2 subunit of F1 domain
Function?
Synchronize the rotation of pore with the gamma subunit and the alpha and beta subunits
____ different conformations that each ______ subunit can undergo.
Depends on the _______________ —> which is determined by ___________ —> which is dependent on
3 different conformations that each beta subunit can undergo
Depends on the beta subunit interaction with gamma —> which is determined by the rotation of the C ring —> which is dependent on H+ movement
What are the 3 different conformations that each beta subunit of the F1 domain can undergo ?
- O “open”
- L “loose
- T “tight”
O “open” conf of beta subunit
Bring in ADP and Pi
Release ATP
L “loose” conf of beta subunit
Binding of ADP + Pi
T “tight” conf of beta subunit
ATP is made but is still bound tightly
Glycolysis
ATP calculation
NADH calculation
2 ATP in
2 ATP made using 1,3-BPG (even)
2 ATP made using phosphoenolpyruvate (net)
2 NADH made by oxidizing glyceraldehyde 3-phosphate
(2) Types of shuttles that can be used to transport NADH from the cytoplasm into the mitochondria?
Located where?
- Glycerol 3-phosphate shuttle (muscle)
2. Malate-aspartate shuttle (heart and liver)
Glycerol 3-phosphate shuttle gives ____ ATP per 1 NADH.
Why?
1.5 ATP per 1 NADH
FAD is used as shuttle prosthetic group —> donor of those e- to ETC is FADH2
Glycerol 3-phosphate shuttle mechanism
- In cytoplasm, glycolytic intermediate dihydroxyacetone phosphate accepts e- from NADH to regenerate NAD+ catalyzed by cytoplasmic glycerol 3-phosphate dehydrogenase.
- Becomes glycerol 3-phosphate
- Donates e- to mitochondrial glycerol 3-phosphate dehydrogenase which used FAD as shuttle prosthetic group
- FADH2 donates those e- to ETC complex II
PDC
NADH calculations
2 NADH
Citric acid Cycle
ATP, NADH, FADH2 calculations
2 ATP using 2 succinyl CoA
6 NADH by oxidizing 2 molecules each of isocitrate, alpha-ketoglutarate, and malate
2 FADH2 by oxidizing 2 molecules of succinate
Total ATP per 1 glucose
but…
30
Amount can differ slightly between organisms because C subunits can vary.
More C subunits —> More H+ able to bind —> More ATP can be made
Electron transfer and _________ are tightly coupled
ATP synthesis
ATP synthesis correlates to?
2
How fast ATP is used or needed in the cell
- Rate of ATP utilization
- Rate of oxygen consumption
Blocking of ETC at any point ___________
Prevents ATP synthesis
Blocking/inhibiting ATP synthase ______________ because?
Slows down ETC because buildup of NADH which feeds back and negatively allosterically modifies enzymes
Rate of ATP utilization:
If use ATP —>
What in mitochondria determines how fast ETC goes?
If use ATP —> elevated ADP and AMP —> make more ATP
ADP in mitochondria
(All other types of regulation we’ve talked about still applies)
Rate of oxygen consumption:
Make ATP use —>
Make ATP use —> faster ETC —> increase O2 consumption
If metabolism increases ……
Increased blood flow to tissues (skel muscle) —> deliver more O2 via hemoglobin to tissues to carry out aerobic respiration
Because metabolizing, H+ and CO2 are produced —> make up Bohr effect which also promotes O2 delivery to tissues
In vitro system with isolated mitochondria
Measures?
What happens when ADP is added? Explain.
Measures O2 consumption over time
When ADP is added —> rapid rate of O2 consumption
Therefore, this explains that ADP increases the rate of ETC because need to make more ATP and increase the rate of O2 consumption
O2 consumption is a measure of ?
The rate of the ETC
If you are using ATP —> _____ conc rise and _________
ADP conc increases —> ETC increases to continue to maintain proton gradient (pmf)
ETC senses the ________
Proton motive force
When the pmf drops because more protons are going through ATP synthase to make ATP, what happens?
The drop in pmf is a signal to the ETC to increase
If need ATP generation…..
ETC works harder so needs a source of e- and H+ from NADH and FADH2
Get those from TCA cycle so that will increase too because of NAD+ and FADH regeneration
If stop ATP generation, what happens?
pmf rises —> ETC slows —> less NADH oxidized to NAD+ —> NADH feeds back and inhibits enzymes
__________ controls the rate of O2 consumption.
ADP concentration
__________ is dependent on its rate of utilization.
ATP synthesis
Electrons do not flow from fuel oxidation to O2 unless _________.
ATP needs to be synthesized/consumed
How is ATP and ADP transported across the inner mitochondrial membrane?
Enzyme: ATP-ADP translocase
Which is located in the inner mitochondrial membrane
*An even exchange: ADP enters only if ATP exists, ATP does not exit unless ADP comes in
Process of ADP - ATP even exchange
ADP from cytoplasm binds to ATP-ADP translocase —> conf change so now ADP is exposed to the matrix of mitochondria —> ADP released into mitochondria —> ATP from matrix binds to that site —> reverse conf change —> ATP released into cytoplasm
3 mechanisms of ATP synthesis
- Respiratory inhibitors
- Direct inhibition of ATP synthase
- Uncouplers
Significance of respiratory inhibitors
Blocks the transfer of electrons at various points therefore ATP synthase is also blocked.
Consequence of respiratory inhibitors
ATP synthesis inhibited.
Rotenone and amytal
- Block Complex I
- Electrons don’t move to CoQ —> NADH builds up —> TCA cycle slows down because NADH is negative allosteric modifier of isocitrate dehydrogenase
Antimycin A
Inhibits complex III
CN- , N3- , CO
- All inhibit complex IV
- CN- and N3- bind to Fe3+ of heme a3
- CO binds to Fe2+ of heme a3
- Prevent the oxidation/reduction because if the iron becomes reduced it eventually has to be reset to be oxidized if it is going to accept more electrons to keep the reaction going.
- PREVENT THE RELEASE OF ELECTRONS TO OXYGEN
CO affects both?
Oxygen delivery and mitochondrial respiration/ability to generate ATP
— — > can only survive by glycolysis
Direct inhibition of ATP synthase
- 2 examples
Consequence?
Ex: Oligomycin - inhibits F0
Ex: DCCD
Consequence: ETC is inhibited and ATP synthesis is inhibited.
Uncouplers
- 2 types
- Consequence
- Can be chemical or physiological
Consequence: Disrupt the tight coupling between electron transport and oxidative phosphorylation by dissipating the proton gradient —> NO ATP SYNTHESIS
Mechanism of uncouplers
Carry protons back into matrix independent of ATP synthase
Pmf drops —> ETC rate increases —> TCA cycle increases —> “burning fuel with no ATP synthesis”
2 things that occur due to uncoupling
Explain each.
- Energy is released as heat- physiological advantage is maintenance of body temp
- Excessive oxygen consumption- utilization of substrate and electron still occur but no proton gradient and no ATP formed
Chemical uncouplers
General properties (2)
- Hydrophobic
- Have a dissociable proton therefore have a pKa and are subject to pH gradient in mitochondria
Chemical uncouplers are ________ in IMS and ________ in matrix
Protonated in IMS
Deprotonated in matrix
Mechanisms of chemical uncouplers
Protons do not go through F0 —> pmf decreases —> ETC increases —> TCA increases —> no ATP being made —> energy lost as heat
Examples of chemical uncouplers (3)
- Dinitrophenol
- Dicumarol
- FCCP
Physiological uncoupler example
UCP-1
UCP-1
Where?
Activated by?
Does what?
- Integral proton channel in mitochondrial membrane
- Activated by fatty acids
- Brings H+ into the matrix independent of ATP synthase
Advantage: generating heat
In hibernating animals, ________ increases in activity to ________. What allows this to occur?
UCP-1
To maintain body temp for normals processes when metabolic rate slows down.
Excess adipose tissue
Brown adipose tissue in infants
Thermogenin (UCP-1) highly expressed here
Because not yet developed full ability to regulate their body temperature
Brown adipose tissue in adult humans
- Not lipid storage
- Highly metabolic, lots of mitochondria
Exposure to cold PET-CT scan result
- Stimulates sympathetic NS
- Found that BAT accumulates in shoulder blades and chest area
Lean vs. Obese study result in adults
- Given ephedrine which also stimulates sympathetic NS
- BAT not activated in obese people (Could BAT stimulation help lose weight by promoting burning stored fat?)
- BAT in lean people activated in same areas as cold exposure study
