Exam 2 Lecture #6 (ZIMA) Flashcards
The final step in oxidation of carbs and fatty acids are located in the mitochondria where energy accumulated in _______________.
Mitochondria have two membranes:_________.
These membranes create two seperated spaces:____________.
The final step in oxidation of carbs and fatty acids are located in mitochondria where energy accumulated in NADH and FADH2 is transformed into energy of ATP - “oxidative phosphorylation”
Mitochondria have two membranes: outer and inner membrane (forms cristae)
These membranes create two seperated spaces: intermembrane and matrix
What enzymes are within intermembrane space?
Purpose of outer membrane “porin”?
What enzymes are on the inner membrane?
Which enzymes are within the matrix space?
The intermembrane space: kinases involved in transfer of the high energy bond of ATP
The outer membrane: porin (channel for many molecules with MW < 10kDa)
The inner membrane: the most complex membrane (enzymes of ETC, ATPase, and several transporters)
The matrix space: enzymes of TCA cycle and beta oxidation, mtDNA, ribosomes
NADH and FADH2 are ______ by the ETC, which is ________
ETC is a sequence of _________ rxns
Potential at which an electron donor gives up its e- to electron acceptor is expressed as the ______
NADH and FADH2 are oxidized by the ETC, a system of e carriers and emzymes (oxidoreductases)
ETC is a sequence of redox rxn’s
(OILRIG)
Potential at which an electron donor gives up its electron to the electron acceptor is expressed as the redox potential
Redox couples with a large negative potential will do what vs a more positive redox potential?
More negative equation: will be the one that loses electrons
The more positive redox potential won’t lose electrons
How much energy is in one mol of ATP?
48-49 kJ/mol
Give an overview of what the ETC does
ETC:
The ETC oxidizes NADH and FADH2 by transferring electrons in several steps to oxygen, while capturing the free energy of the redox rx’s to drive the synthesis of ATP.
During this process, H+ are pumped from the matrix across the inner membrane to form the H+ gradient which provides energy for ATP synthesis.
In the ETC, the electron cacrriers are grouped into four large multisubunit complexes (I-IV)
Which molecule has the lowest redox potential (most negative)… vs which molecule has the highest redox potential (most positive)
NADH has the most negative redox potential (it wants to lose electrons, wants to get oxidized)
O2 has the most positive redox potential (it wants to gain electrons, wants to get reduced)
Complex I is the most complicated and consists of at least ______
Complex I oxidizes ____ and transfers e- to _____
Explain the Steps
How many total protons are shuttled by complex I
Complex I is the most complicated and consists of at least 40 different polypeptides (1MDa)
Complex I oxidizes NADH and transfers electrons to ubiquinone (coenzyme Q)
Step 1: transfer of 2e- to NADH to cofactor FMN within the complex
Step 2: transfer of 2e- from FMN to Fe-S centers of complex
Step 3: transfer of 2e- from a Fe-S center of the complex to UQ
COMPLEX 1 shuttles 4 H+
What is the name of complex I?
Complex I is NADH dehydrogenase
(also uses FMN and Fe-S)
What is the name of complex II
Complex II: succinate dehydrogenase
Complex II catalyzes oxidation of ____ and consists of ___ subunits.
During oxidation of ____ by Complex II, ___ e- and __ H+ are transfered to _____
The small amount of energy liberated during complex II is ____ for H+ pumping across the membrane
Complex II catalyzes oxidiation of succinate and consists of four subunits (one contains FAD, another contains Fe-S)
During oxidation of succinate by Complex II, 2 e- and 2H+ are transferred to FAD, creating FADH2
The small amount of energy liberated during the oxidation of succinate is insufficient for H+ pumping across the membrane.
Which complex does NOT pump any H+ across the membrane?
Complex II doesn’t pump any protons
What is the name of complex II
Complex II: succinate dehydrogenase
What is the name of complex III
Complex III: cytochrome bc1
Complex III catalyzes transfer of e- from ___ to _____, and pumps ___ across the inner membrane
Complex III consists of ______ subunits, including how many alpha helixes?
Complex III catalyzes transfer of electrons from UQ to cytochrome c coupled to the translocation of 4 H+ across the inner membrane.
Complex III consists of 11 subunits containing eight alpha helixes?
Cytochrome c contain _________ group
In ETC, there are three classess of cytochrome c(______)
From complex III, electrons are transfered to____
Cytochrome c is a small/large globular protein that is hydrophobic/hydrophillic with a ___ group.
Cytochrome c functions as a ______ in the ETC
Cytochrome c contain Fe- containing heme group
In ETC there are three classes of cytochrome c: a, b, and c
From Complex III, electrons are transferred to cytochrome c
Cytochrome c is a small globular hydrophillic protein with a heme group
Cytochrome c (like Uq) functions as a mobile e- carrier in the ETC
What is the name of Complex IV?
Complex IV: cytochrome c oxidase
Complex IV catalyzes transfer of e- from ___ to ____
Complex IV consists of ____ subunits and contains as redox components_____ and ______
Complex IV: catalyzes transfer of electrons from cytochrome c to O2 (which is the terminal electron acceptor) to form H20 coupled to the translocation of H+ across the inner membrane.
Complex 4 consists of 13 subunits and contains as redox components: two cytochrome and two copper centers
Transfer of e- through Complex IV:
Step 1:
Step 2:
Step 3:
Complex IV:
Step 1: electrons are transferred from cytochrome c to the Cua site on subunit II
Step 2: then e- are transferred to heme a in subunit 1
Step 3: e- are moved to the Cub and heme a3 redox center, where the final transfer of e- to O2 occurs
The transfer of 2 e- through complex IV is associated with the uptake of 2 H+ from matrix
Explain how the ETC and proton pumping are related
What does that do to the two sides of the membrane?
Which side becomes more acidic, which side becomes more alkaline?
The energy released during the electron transfer through the ETC is used to pump H+ across the inner membrane (H+ gradient). This creates a difference in H+ concentration on the two sides of the membrane. The intermembrane space becomes more acidic and the matrix becomes more alkaline.
How many protons are pumped across in total by the ETC?
What is the free energy available from this process?
During the transfer of 2 e- from NADH to O2 approximately 10 protons are pumped across the membrane to establish the electrochemical gradient.
The free energy available from this process DELTAG= -219 kJ/mol (enough energy to produce 3 ATP)
How many protons are pumped in each complex?
Protons Pumped in the ETC:
Complex I: 4 H+
Complex II: 0
Complex 3: 4 H+
Complex 4: 2 H+
The need for ATP in a cell regulates _____
ADP does what to the rate of ATP synthesis and thus 02 consumption rate
The need for ATP in a cell (energy demand) regulates the rate of ATP synthesis in mitochondria, which in turn regulates the rate of the ETC.
ADP increases the rate of ATP synthesis and flux of e- through the ETC, thus leading to a higher rate of O2 consumption
THUS, rate of electron transport is tightly coupled to ATP synthesis
Explain what oligomycin does
Explain what protonophores (DNF, FCCP, and CCCP) do
Oligomycin is an inhibitor of ATP synthase, preventing the movement of H+ through ATP synthase. This will slow the electron flux via the ETC and thus the rate of O2 consumption
Protonophores will uncouple the electron transport through the ETC and ATP synthesis… in the presence of protonophores, electron transport many continue but without ATP synthesis
ATP Synthase:
What does ATP Synthase do?
Explain the F1 and Fo domains
ATP Synthase (complex V) catalyzes ATP production using the energy of the proton gradient
F1 domain catalyzes the binding sites for ATP and ADP and catalyzes ATP synthesis
Fo domain provides channel for H+ movement
Mitochondrial ROS formation
O2- is generated at complex I and complex III
O2- is not permeable but can pass through ion channels
o2- is then turned into H2O2 in the matrix
