BIOCHEM Citric Acid Cycle, Saccharides, Glycolysis Flashcards
(76 cards)
is the final common pathway for the oxidation of carbohydrate, lipid, and protein because glucose,
fatty acids, and most amino acids are metabolized to acetyl CoA or intermediates of the cycle.
Citric Acid Cycle
Krebs Cycle has a central role in ____________, ____________, and ______________________
Gluconeogenesis, Lipogenesis, Interconversion of amino acids.
The cycle starts with reaction between the acetyl moiety of
____________ and the four-carbon dicarboxylic acid __________, forming a six-carbon tricarboxylic acid,__________ . In the subsequent reactions, two molecules of _______ are released and oxaloacetate is regenerated
acetyl-CoA, oxaloacetate, citrate, CO2
________________ provides the main pathway for ATP
formation linked to the oxidation of metabolic fuels
The citric acid cycle
The citric acid cycle process is ________, requiring __________ as the final oxidant of the reduced coenzymes
aerobic, oxygen
The enzymes of the citric acid cycle are located in the __________________, either free or attached to the inner ______________ membrane
mitochondrial matrix, mitochondrial
Entry of Carbon
Anaplerosis
Exit of Carbon
Cataplerosis
The initial reaction between acetyl-CoA and oxaloacetate
(C4) to form citrate (C6) is catalyzed by
citrate synthase
Citrate is isomerized to isocitrate by the enzyme
aconitase
________ ATP ARE FORMED PER TURN OF THE CITRIC ACID CYCLE
TEN
Four of the B vitamins are essential in the citric acid cycle and hence energy-yielding metabolism:
riboflavin, niacin, thiamin (vitamin B1), pantothenic acid
_________, as FAD, is the cofactor for succinate dehydrogenase;
riboflavin
_________, as NAD+ , is the electron acceptor for isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and malate dehydrogenase;
niacin
________, as thiamin diphosphate, is the coenzyme for decarboxylation in the α- ketoglutarate dehydrogenase reaction; and
thiamin (vitamin B1)
__________, as part of coenzyme A, is esterified to carboxylic acids to form acetyl CoA and succinyl-CoA.
pantothenic acid
All the intermediates of the Krebs cycle are potentially ___________, since they can give rise to oxaloacetate, and hence production of glucose
glucogenic
The key enzyme that catalyzes transfer out of the cycle into gluconeogenesis is _________________________, which catalyzes the decarboxylation of oxaloacetate to phosphoenolpyruvate, with GTP acting as
the phosphate donor
phosphoenolpyruvate carboxykinase
___________________ reactions form pyruvate from alanine, oxaloacetate from aspartate, and α-ketoglutarate from glutamate
aminotransferase
Acetyl-CoA, formed from pyruvate by the action of pyruvate dehydrogenase, is the major substrate for ________________________________ synthesis in nonruminants
long-chain fatty acid
In most tissues, where the primary role of the citric acid cycle is in energy-yielding metabolism, _________________via the respiratory chain and oxidative phosphorylation regulates citric acid cycle activity
respiratory control
The citric acid cycle is _____________, since in addition to
oxidation it is important in the provision of ____________________ for gluconeogenesis, ______________ for fatty acid synthesis, and interconversion of amino acids. For these processes to be sustained they rely on a balance of anaplerosis and cataplerosis in the citric acid cycle
amphibolic, carbon skeletons, acetyl-CoA
Producers of NADH+ in Krebs Cycle
Conversion of Isocitrate to Alpha-Ketoglutarate
Conversion of Alpha-Ketoglutarate to Succinyl-CoA
Conversion of Malate to Oxaloacetate
Producers of FADH in Krebs Cycle
Conversion of Succinate to Fumarate
