Question

Oxidative phosphorylation is a process that occurs in the _______________ of mitochondria. It requires an electron-transport chain that operates on the high-energy electrons taken from the activated carrier molecules+ _____________ and _______________ that are produced by glycolysis and the citric acid cycle. These electrons are transferred through a series of molecules, and the energy released during these transfers is used to generate a gradient of _____________. Since their concentration is much __________________ outside than inside the mitochondria, the flow of __________________ down the concentration gradient is energetically very __________________ and can thus be coupled to the production of _______ from ______. Thus, oxidative phosphorylation refers to the oxidation of __________________ and __________________ molecules and the phosphorylation of __________________. Without this process, the yield of ATP from each glucose molecule would be __________________ decreased.

Word Bank:

ADP

GTP

cytosol

higher

FADH2

lower

GDP

moderately

NAD+
Pi
severely favorable

unfavorable

ATP

electrons

matrix

slightly

H+
inner membrane

NADH + H+

--------

The classical point of view is that, during mitochondrial respiration, three ATP molecules can be generated from one molecule of NADH + H+ and only two from FADH2. When factoring in the cytosolic NADH + H+, the maximum number of molecules of ATP per glucose generated by the electron transport system is _____.
a) 2 b) 4 c) 36 d) 38

-------

In step 1 of the Krebs cycle is the condensation of a C2 subunit (from acetyl-S-CoA) and oxaloacetate, a C4 dicarboxylic acid to form citric acid, a C6 tricarboxylic acid (hence the alternative names citric acid cycle and tricarboxylic acid cycle).

a) To regenerate the C4 oxaloacetate, there are two CO2 molecules where did those two carbons go?
b) What is the importance of the release of these carbons?
c) How did Sir Hans Krebs that the interconversions among tri- and dicarboxylic acids are a cyclic pathway?

d) What type of inhibitor is malonate and what step does it block in the Krebs cycle?

Answer 1

1)Oxidative phosphorylation is a process that occurs in the INNER MEMBRANE of mitochondria.
-It requires an electron-transport chain that operates on the high-energy electrons taken from the activated carrier molecules NADH+H+ and FADH2 that are produced by glycolysis and the citric acid cycle.
-These electrons are transferred through a series of molecules, and the energy released during these transfers is used to generate a gradient of H+. Since their concentration is much HIGHER outside than inside the mitochondria, the flow of H+ down the concentration gradient is energetically very SEVERLY FAVOURABLE and can thus be coupled to the production of ATP from ADP.
-Thus, oxidative phosphorylation refers to the oxidation of NADH+H+ and FADH2 molecules and the phosphorylation of ADP.

-Without this process, the yield of ATP from each glucose molecule would be MODERATELY decreased.

(2) Correct answer:- (d) 38 ATP

(3) (a) In the reaction oxalo- Succinate (6 carbon) to alpha ketoglutarate (5 carbon) and CO2 is released.
- then alpha-ketoglutarate (5 carbon) is converted to succinyl CoA (4 carbon) and CO2 is released.
(b) by releasing these CO2, a 6 carbon is converted to 4 C compound.
(c) krebs cycle is a cyclic pathway because oxaloacetate is regenerated.
(d) Malonate is a competitive inhibitor of the enzyme succinate dehydrogenase.