metabolic regulation Flashcards
How is the ETC/ATP synthase regulated? including consequences of inhibition
negative: ATP
pos: ADP + Pi
consequences of inhibition: accumulation of NADH
how is alpha-ketoglutarate DH regulated? including consequences of inhibition
neg: NADH
pos: none
consequences of inhibition: lower oxaloacetate
how is isocitrate DH regulated? including consequences of inhibition
neg: NADH, ATP
pos: ADP
consequences of inhibition: accumulation of citrate
how is citrate synthase regulated? including consequences of inhibition
neg: NADH and citrate
pos: acetyl coa and oxaloacetate
consequences of inhibition: accumulation of acetyl coa
how is pyruvate dh regulated?
neg: NADH, acetyl coa
pos: ADP, pyruvate
how is pyruvate kinase regulated?
neg: ATP, NADH, acetyl coa
pos: F-1,6-BP
how is PFK regulated? including consequences of inhibition
neg: ATP, citrate
pos: AMP
consequences of inhibition: lower F-1,6-BP and accumulation of G-6-P
how is hexokinase regulated?
neg: G-6-P
which steps in glycolysis are regulated?
hexokinase, PFK, PK
which steps in TCA cycle are regulated?
citrate synthase, isocitrate DH, alpha-KGDH
Which enzymes does ATP inhibit?
PFK, OK, Citrate synthase, IDH, a-KGDH
Which enzymes for NADH inhibit?
PK, PDH, citrate synthase, IDH, a-KGDH
Which enzymes do ADP/AMP activate?
PFK, PDH, IDH, citrate synthase, a-KGDH
which enzyme does ADP inhibit?
PDH-K
How is the ETC regulated?
(+) ADP + Pi
(-) ATP
What does G-6-P inhibit?
hexokinase
What does citrate inhibit?
PFK and citrate synthase
what does acetyl-coa inhibit?
PK, PDH
what does succinyl coa inhibit?
a-KGDH and citrate synthase
which part of the TCA cycle is regulated mainly by substrate availability?
citrate synthase from acetyl-coa and oxaloacetate
How is PDH regulated?
inhibited by PDH kinase (which is activated by NADH and acetyl coa)
activated by PDH phosphatase (which is activated by insulin)
What are the two ways that electrons from NADH in the cytosol can enter the electron transport chain?
Malate aspartate shuttle and glycerophosphate shuttle
What are the benefits of the malate aspartate shuttle?
more efficient, because NADH is converted back to NADH, so no ATP is lost
What are the benefits of the glycerophosphate shuttle?
Faster because e- are passed directly to an FAD in the inner membrane and the ETC but less efficient because NADH –> FAD means you get less ATP from it
How does Pi from the cytosol enter the mitochondria?
through an H+/Pi symporter
How does the H+/Pi symporter affect ATP synthase?
the H+ go with the pH gradient, thus reducing the H+ gradient used to drive ATP synthase, thereby reducing the energy available for ATP synthesis
How does the Q cycle contribute to the generation of a proton gradient?
Oxidation of CoQH2 on IMS side releases protons to IMS. CoQ is always reduced on matrix side, so it releases protons from matrix to the IMS.
Why does Q cycle contribute more to proton gradient than direct oxidation?
Undergoes multiple oxidations and one then gets rereduced so it leads to two more protons pumped
How does a proton wire work
conformational changes due to e- transfer cause a series of nonconsecutive protonations and deprotonations of amino acid side chains which result in the net transfer of a proton from the matrix to the IMS
What makes FMN and CoQ special electron carriers/acceptors
can accept or transfer 1 or 2 e- at a time
use a transient free radical intermediate (semiquinone)
How many e- can NAD+ carry
obligated to carry 2e-
how many e- can cytochromes carry/transfer
usually 1
describe structure, location, and mechanism of electron transfer for CoQ
organic, lipid soluble molecule
located in the mitochondrial inner membrane
transfers 2 e- from C1 or 2 to C3 and carries 2H+ from matrix to IMS
describe structure, location, and mechanism of electron transfer for cytochrome C
water soluble protein with a heme prosthetic group
found in IMS
carries 1 e- from C3 to C4
What allows cytochromes to have different reduction potentials
the different microenvironments of the heme groups and the varying microenvironments of the proteins themselves
what is an advantage of the Q cycle in C3
allows for 4H+ to be pumped into IMS instead of 2 from direct oxidation
how are protons pumped in each complex of ETC
1: proton wire
2: not
3: Q cycle
4: proton wire
What is the chemiosmotic hypothesis?
during the ETC, protons are transferred from the mito matrix to the IMS, generating a proton gradient. The dissipation of this drives ATP synthesis
experimental observations which support chemiosmotic theory
a. Can measure the pH gradient across the mitochondrial inner membrane (membrane is impermeable to ions)
b. Artificial pH gradient results in ATP synthesis
c. Electron transport acidifies the cytosol
d. ATP synthesis requires intact mitochondria
e. Agents which destroy the pH gradient (uncouplers) prevent ATP synthesis
where is Fo subunit located and what does it do
transmembrane unit which converts flow of protons into mechanical movement
How is mechanical movement from Fo converted to ATP
communicated down the stalk portion to F1 unit which triggers conformational changes to drive ATP synthesis
Where is F1 subunit located and what does it do
soluble unit in mitochondrial matrix and faciliatates conformational changes to drive ATP synthesis
