SM4 Flashcards
(17 cards)
How do you protect electron carriers from water and why is this important?
Water can be broken into free radicals if the electron binds to it. One way is to embed the heme or iron-sulfur in hydrophobic pocket of residues.
How does the Malate-Aspartate shuttle work?
Cytosolic NADH is used to reduce cytosolic oxaloacetate (OAA) to malate. Malate is transported across the inner membrane in exchange for α-ketoglutarate by a specific translocase. In the matrix, malate is oxidized back to OAA (during which time NAD is reduced so electrons can go to ETC) by mitochondrial malate dehydrogenase regenerating NADH. The newly formed OAA is transaminated to aspartate that is then transported to the cytoplasm in exchange for glutamate, where it is then deaminated to for OAA.
NADH is produced during glycolysis in the cytoplasm. How do we get the electrons from NADH into the mitrochondrial matrix if the inner membrane is impermeable?
Glycerol 3-P Shuttle. G3P dehydrogenase trasnfers the electrons from NADH to DHAP to form Glycerol 3-P. This then will donate the electrons to inner-membrane bound FAD-dependent G3P dehydrogenase and regenerate DHAP in the process. G3P DH transfers to electrons to CoQ
Rate of ETC is controlled by concentration of ATP
F; It is controlled by concentration of ADP
What ensures flow successively through the ETC?
Each successive complex has a more positive reduction potential creating a unidirectional flow of electrons.
What is the role of copper in complex IV of the ETC?
copper ions that facilitate the collection of the four electrons required to fully reduce O2 to H2O.
What kind of enzymes are in the mitochondrial matrix?
The enzymes responsible for the oxidation of pyruvate, amino acids, fatty acids (β-oxidation), and the TCA cycle. Glucose, urea, and heme synthesis also partially occur in the matrix.
Which complex of the ETC contains the G3P DH assoc with the G3P shuttle?
Complex II
Which complexes of the ETC are proton pumps?
I, III and IV
What do molecules like Cyanide, carbon monoxide (CO), hydrogen sulfide (H2S), and sodium azide do?
They bind to the iron in the heme of the cytochrome aa3 component of cytochrome oxidase in Complex IV preventing electron transfer to O2
What are uncoupling drugs?
They uncouple ETC from ATP synthesis by dissipating the proton gradient across in the inner membrane. Natural protein = thermogenin (brown fat in infants). Another ex: 2,4 DNP (dissipates the proton gradient) - 1930s it was advertised as good way to loose weight.
What drives transport of ADP and ATP across inner mitochondrial membrane? What about transport of pyruvate?
Voltage gradient. pH gradient.
What triggers formation of The Mitochondrial Permeability Transition Pore (MPTP)?
apoptosis
what are sources of ROS?
- CoQ
- Oxidases, peroxidases, and oxygenases (cytochrome p450 enzymes)
- Ionizing radiation from cosmic rays, radioactivity, and X-rays.
Why must iron be protected?
If hydrogen peroxide encounters iron in proper oxidation state it can generate hydroxyl radical.
How does glutathione act as a antioxidant?
It has a free -SH. Two GSH will form disulfide bond, and that oxidation reaction will reduce H2O2 into H2). The Glutathione is then regeneration with NADPH from pentose phosphate pathway as the electron donor.
Name some non-enzymatic antioxidants?
Vitamins C, E; Cartenoids, Flaveniods, Uric Acid, Melatonin
