ATP synthase Flashcards
What is the proton-motive force?
Proton = chemical potential (inside alkan)
Motive = electrical potential (inside neg)
Energy-rich, unequal distribution of protons
ATP synthase has two subdivisions for its structure:
F0: c-ring and a, which act as anchor to membrane and provide a transmembrane path for protons = proton channel
F1: 3B, 3a, y subunit = central shaft and forces B subunits into different conformations
ATP synthase forms
dimers which stabilize the enzyme
What are the moving parts of ATP synthase?
Y, E, C-ring
ATP synthase active sites (alpha and beta) function:
As Y moves, each beta subunit change conformation
1) Trapping of ADP and Pi
2) ATP synthesis
3) ATP release and ADP and Pi binding
What are the 3 conformations of the beta subunits?
L = loose, conformation that binds ADP and Pi T = tight, conformation that binds ATP with great avidity that it converts bound ADP and Pi into ATP O = open, conformation that can bind or release adenine nucleotides
Both the L and T conformations cannot release
bound nucleotides
What causes the 3 active sites to change functions?
The proton motive force: as protons flow through the membrane-embedded component of the enzyme
Order of conformation of active sites
L -> T -> O
Remember Y only “clicks” or moves once in the first step!
How do protons flow through F0 and drive the rotation of the y subunit?
The a subunit is positioned so that each half-channel directly interacts with one c subunit
The a unit remains stationary as the c-ring rotates
H+ enter the IM half channel, than the c-ring rotates until the H+ meets the other half channel, then H+ is released through matrix channel to matrix
Each 360-degree rotation of the Y subunit leads to the
synthesis and release of 3 molecules of ATP
Electrons from cytoplasmic NADH enter the mitochondria by shuttles
1) glycerol 3-phosphate shuttle (skeletal muscle and brain): 2e-/H from NADH added to glycerol 3-phosphate which then enters into glycerol 3-phosphate dehydrogenase and gives up 2H/2e- to FAD = FADH2 which gives H/e- to QH2 in the mitochondrial membrane
Malate-aspartate shuttle
In the liver, kidney, and heart
Antiporter transport protein channels
Aspartate leaves matrix via glutamate entering, aspartate turned into glutamate in the IMS, which then enters matrix, then turned into asparatate
In IMS: alpha-ketoglutarate to oxaloactate to malate from NADH to NAD+, malate enters matrix as alpha-ketoglutarate leaves, malates turned back into oxaloacetate via NAD+ then NADH, then into alpha-ketoglutarate, then repeat!
Final ATP amount
30 or 32
Final ATP from glycolysis from 2NADH depends on the shuttle used
Regulation of the rate of oxidative phosphorylation by the ADP level is called
Respiratory control or acceptor control
ADP indirectly affects the rate of the citric acid cycle
