Chapter 16 Biochemistry

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The citric acid cycle has two other names:
Tricarboxylic acid cycle, Kreb’s cycle
Which of the following is(are) not involved in krebs cycle?
Pryruvate and Glyceraldehyde 3-Phosphate
In biochemistry, cellular respiration is that cells consume O2 and produce CO2. It occurs in four major stages, and in the second stage, the acetyl groups are fed into the citric acid cycle.
False
Pryuvate, derived from glucose and other sugars by glycolysis, is oxidized to acetyl-CoA and CO2 by the pryuvate dehydrogenase (PDH) complex, a cluster of enzymes-multiple copies of each of three enzymes-located in the mitochondria of eukaryotic cells and in the cytosol of bacteria.
True
The pryuvate dehydrogenase (PDH) complex is a multienzyme complex in which a series of chemical intermediates remain bound to the enzyme molecules as a substrate is transformed into the final product. Only four coenzymes participate in the reaction mechanism.
False
Biotin participates in the decarboxylation catalyzed by the pyruvate dehydrogenase complex, and both NAD+ and a Flavin nucleotides act a electron carries.
False
In the beginning of the CAC, acetyl-CoA donates its acetyl group to the four-carbon compound citrate to form the six-carbon oxaloacetate.
False
In the CAC, four of the eight steps are oxidations, in which the energy of oxidation is very efficiently, conserved in the form of reduced coenzymes NADH and FADH2.
True
Which combination of cofactors is involved in the conversion of pyruvate acetyl-CoA?
TPP, lipoic acid, and NAD+
Malonate is a competitive inhibitor of succinate dehydrogenase If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds would you expect to decrease in concentration?
Fumarate
In mammals, which of the following occur(s) during the citric acid cycle (select all that apply):
formation of ?-ketoglutarate, generation of NADH and FADH2, metabolism of acetate to carbon dioxide and water, oxidation of acetyl-CoA
Which of the following reaction generates GTP (ATP) in the CAC?
Succinyl-CoA to succinate
The two-step reactions in the CAC, in which the reactants lose CO2 are the following:
alpha-ketoglutarate to succinyl-CoA, and Isocitrate to alpha-ketoglutarate
The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields _ mol of NADH, _ mol of FADH2, and _ mol of ATP (or GTP).
4;1;1
Pyruvate is produced in glycolysis and used by kreb’s Cycle in the mitochondrial matrix. How does pyruvate get into the matrix?
Facilitated diffusion through a specific uniport
Which of the following Kreb’s Cycle reactions is often followed rapidly by a transphosphorylation?
Succinyl-CoA synthetase
What two chemical mechanisms change pyruvate acetyl-CoA in the pyruvate dehydrogenase complex?
Dehydrogenation and decarboxylation
How many reducing equivalents are transferred to electron carriers after one turn of the Citric Acid Cycle?
8
Using currently accepted P/O ratio (NADH-2.5ATP, 1 FADH2-1.5ATP), what is the total ATP potential yield from one Acetyl-CoA in the Citric Acid Cycle?
10
The power of kreb’s Cycle is partly in the ability to shuttle intermediates out for the synthesis of important groups of molecules. What group of molecule is produced from Citrate?
Lipids and sterols
The release of carbon dioxide from the complete oxidation of pyruvate can pose problems for cells. What molecule can easily be formed from carbon dioxide that can serve as a one carbon donor and double as a biological buffer?
Biocarbonate
The Citric Acid Cycle is regulated in a manner similar to Glycolysis. Which molecule is an allosteric activator of both of those pathways?
ADP
The Glyoxylate Cycle is remarkably similar to kreb’s Cycle, but differs in several important ways. What important molecule is conserved by the Glyoxylate Cycle but not Kreb’s?
Carbon dioxide
How many NADH molecules are generated from the complete oxidation of one Glucose?
10
Categories: Biochemistry