Exam 3: Oxidative Phosphorylation Flashcards
In the electron transport chain, are protons pumped with or against their concentration gradient?
Against its gradient.
What are three requirements of chemiosmotic energy coupling?
- Membrane impermeable ions.
- Membrane must contain proteins that couple the “downhill” flow of electrons in the ETC to the “uphill” flow to protons across the membrane.
- Membrane must also contain a protein that couples the “downhill” flow of protons to the phosphorylation of ADP.
Explain how Complex I accepts and donates electrons.
Complex I accepts two electrons from NADH but passes them on individually: one at a time.
What are the reactants and products of Complex I?
NADH + Q + 5(H+) => (NAD+) + QH2 + 4(H+)
What is the principle reaction that occurs in Complex II?
Succinate loses two hydrogens to FAD to form FADH2 and Fumarate.
True or false, Complex II transports protons across the the membrane.
False.
Iron-sulfur clusters, cytochrome bs, and cytochrome cs are contained in which complex?
Complex III.
The Q cycle results in additional protons being added where?
The intermembrane space (IMS).
How many molecules of QH2 become oxidized in the Q cycle?
Two molecules.
In the Q cycle, ______ molecule(s) of Q become reduced using ___ electron(s) from QH2 oxidation.
…one …two …
In Complex IV, how many subunits are there?
13 subunits.
How many heme groups are in Complex IV and what are they called?
Two: a and a3.
What are the two copper ions that are found in Complex IV and what do they do?
CuA accepts electrons from Cyt c and CuB is bonded to heme a3, forming a binuclear center that transfers electrons the the ultimate receiver, oxygen.
Which complexes pump protons into the IMS?
Complex I and Complex IV.
Which complexes add protons to the IMS?
Complex I, III, and IV.
What is the role of iron-sulfur clusters?
They are single electron carriers.
What are cytochromes?
Stationary or mobile proteins or subunits of complexes containing heme prosthetic groups.
What are the roles of cytochrome c?
Cytochrome c is a mobile soluble protein, single electron carrier found in the IMS.
Describe coenyme Q and its functions.
A lipid-soluble conjugate dicarbonyl compound that accepts one or two electrons at a time. Once reduced, it can carry protons and electrons through the membrane.
From where to where does coenzyme Q transport electrons?
From either Complex I or II to Complex III.
By what two methods can cytosolic NADH enter the ETC?
The malate-aspartate shuttle and glycerol 3-P shuttle.
What are the two functional units of the mitochondrial ATP synthase complex?
F1 and F0.
What is the function of F1?
F1 catalyzes the synthesis of ATP from ADP and Pi.
What is the function of F0?
F0 is an integral membrane complex that transports protons from the IMS into the matrix, causing a rotation of the its central shaft subunit, from which energy is transferred into F1 to catalyze the phosphorylation of ADP.
What is the primary form of regulation for oxidative phosphorylation?
Substrate availability: NADH or FADH2 and ADP and Pi.
True or false, substrates are required for both electron transport and ATP synthesis.
True. Due the coupling of reactions, substrates are required for both.
The accumulation of NADH acts to ______ the enzymes of glycolysis and TCA cycle.
…inhibit …
What is IF1 and how does it work?
IF1 is the Inhibitor of F1, which works in the mitochondrial matrix to prevent hydrolysis of ATP during states of low [oxygen] by preventing ATPase from turning backwards.
Is IF1 active at high or low pH?
Low pH, as it is encountered when electron transport is stalled due to low oxygen.
