The structure of the Succinate-coenzyme Q reductase complex in a phospholipid membrane.
The citric acid cycle is the hub of the metabolism, a central wheel from which many spokes radiate. Also known as the tricarboxylic acid cycle (TCA) or Krebs cycle, it is the final common pathway for the oxidative degradation of fuel molecules and also the source of many biosynthetic precursors. As a degradative pathway, the cycle results stoichiometrically in the complete oxidation of an activated acetyl unit to CO2. With each turn of the cycle three NAD+ molecules and one FAD molecule are reduced which may subsequently donate their electrons to the electron transport system of the mitochondrial matrix, producing ATP. Additionally, with each turn of the cycle, one high energy phosphate bond is created by direct substrate level phosphorylation.
Conceptual Vocabulary for Citric Acid Cycle
Glycolysis & Pyruvate Dehydrogenase
Each list begins with basic conceptual vocabulary you need to know for MCAT questions and proceeds to advanced terms that might appear in context in MCAT passages. The terms are links to Wikipedia articles.
Anaerobic organism
An anaerobic organism is any organism that does not require oxygen for growth.
An anaerobic organism is any organism that does not require oxygen for growth.
Adenosine triphosphate
Adenosine triphosphate is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer.
Adenosine triphosphate is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer.
Glycolysis
Glycolysis is the initial process of most carbohydrate catabolism serving the functions of producing ATP and NADH, pyruvate for the citric acid cycle, and a variety of other compounds which are important for biosynthesis.
Glycolysis is the initial process of most carbohydrate catabolism serving the functions of producing ATP and NADH, pyruvate for the citric acid cycle, and a variety of other compounds which are important for biosynthesis.
Pyruvic acid
Pyruvic acid is an alpha-keto acid which plays an important role in biochemical processes. It is an output of glycolysis.
Pyruvic acid is an alpha-keto acid which plays an important role in biochemical processes. It is an output of glycolysis.
Glucose-6-phosphate
Glucose 6-phosphate (also known as Robison ester) is glucose sugar phosphorylated on carbon 6.
Glucose 6-phosphate (also known as Robison ester) is glucose sugar phosphorylated on carbon 6.
Fermentation
Fermentation is respiration under anaerobic conditions with no external electron acceptor.
Fermentation is respiration under anaerobic conditions with no external electron acceptor.
Ethanol fermentation
Ethanol fermentation is the biological process by which sugars such as glucose, fructose, and sucrose, are converted into ethanol and carbon dioxide.
Ethanol fermentation is the biological process by which sugars such as glucose, fructose, and sucrose, are converted into ethanol and carbon dioxide.
Kinase
A kinase, alternatively known as a phosphotransferase, is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific target molecules.
A kinase, alternatively known as a phosphotransferase, is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific target molecules.
Phosphorylation
Phosphorylation is the addition of a phosphate group to a protein molecule or a small molecule.
Phosphorylation is the addition of a phosphate group to a protein molecule or a small molecule.
Fructose 2,6-bisphosphate
Fructose 2,6-bisphosphate, is a metabolite that allosterically affects the activity of the enzymes phosphofructokinase 1 and fructose 1,6-bisphosphatase to regulate glycolysis and gluconeogenesis.
Fructose 2,6-bisphosphate, is a metabolite that allosterically affects the activity of the enzymes phosphofructokinase 1 and fructose 1,6-bisphosphatase to regulate glycolysis and gluconeogenesis.
Futile cycle
A futile cycle is when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than wasting energy.
A futile cycle is when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than wasting energy.
Fructose 6-phosphate
Fructose 6-phosphate (also known as the Neuberg ester) is fructose sugar phosphorylated on carbon 6. The beta-D-form of this compound is very common in cells.
Fructose 6-phosphate (also known as the Neuberg ester) is fructose sugar phosphorylated on carbon 6. The beta-D-form of this compound is very common in cells.
Lactate
L-lactate is constantly produced in animals from pyruvate in a process of fermentation during normal metabolism and exercise.
L-lactate is constantly produced in animals from pyruvate in a process of fermentation during normal metabolism and exercise.
Lactic acid fermentation
Lactic acid fermentation is a form of anaerobic respiration that occurs in some bacteria and animal cells in the absence of oxygen.
Lactic acid fermentation is a form of anaerobic respiration that occurs in some bacteria and animal cells in the absence of oxygen.
Adenosine monophosphate
Adenosine monophosphate is an ester of phosphoric acid with the nucleoside adenosine. AMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase adenine.
Adenosine monophosphate is an ester of phosphoric acid with the nucleoside adenosine. AMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase adenine.
Substrate-level phosphorylation
Substrate-level phosphorylation is a type of chemical reaction that results in the formation of ATP by the direct transfer of a phosphate group to ADP from a reactive intermediate.
Substrate-level phosphorylation is a type of chemical reaction that results in the formation of ATP by the direct transfer of a phosphate group to ADP from a reactive intermediate.
Pyruvate decarboxylation
The pyruvate decarboxylation reaction links the metabolic pathways glycolysis and the citric acid cycle.
The pyruvate decarboxylation reaction links the metabolic pathways glycolysis and the citric acid cycle.
1,3-Bisphosphoglycerate
In glycolysis and photosynthesis, 1,3-Bisphosphoglycerate (1,3BPG) is a transitional stage between glycerate 3-phosphate and glyceraldehyde 3-phosphate during the fixation or reduction, respectively, of carbon dioxide.
In glycolysis and photosynthesis, 1,3-Bisphosphoglycerate (1,3BPG) is a transitional stage between glycerate 3-phosphate and glyceraldehyde 3-phosphate during the fixation or reduction, respectively, of carbon dioxide.
2-Phosphoglycerate
2-Phosphoglycerate (2PG) is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate (PEP), the penultimate step in the conversion of glucose to pyruvate.
2-Phosphoglycerate (2PG) is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate (PEP), the penultimate step in the conversion of glucose to pyruvate.
Hexokinase
A hexokinase is an enzyme that phosphorylates a six-carbon sugar, a hexose, to a hexose phosphate.
A hexokinase is an enzyme that phosphorylates a six-carbon sugar, a hexose, to a hexose phosphate.
Enolase
Enolase, or 2-phospho-D-glycerate hydrolyase, is an enzyme that participates in glycolysis, catalyzing the conversion of 2-phosphoglycerate to phosphoenolpyruvate, the penultimate step in the conversion of glucose to pyruvate.
Enolase, or 2-phospho-D-glycerate hydrolyase, is an enzyme that participates in glycolysis, catalyzing the conversion of 2-phosphoglycerate to phosphoenolpyruvate, the penultimate step in the conversion of glucose to pyruvate.
Pyruvate kinase
Pyruvate kinase is an enzyme involved in glycolysis, catalyzing the transfer of a phosphate group from phosphoenolpyruvate (PEP) to ADP, yielding a pyruvate molecule and producing one molecule ATP.
Pyruvate kinase is an enzyme involved in glycolysis, catalyzing the transfer of a phosphate group from phosphoenolpyruvate (PEP) to ADP, yielding a pyruvate molecule and producing one molecule ATP.
Pyruvate dehydrogenase complex
Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that transform pyruvate into acetyl-CoA.
Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that transform pyruvate into acetyl-CoA.
Entner-Doudoroff Pathway
The Entner-Doudoroff pathway in some prokaryotes describes a series of reactions that catabolize glucose to pyruvate using a different set of enzymes from those used in either glycolysis or the pentose phosphate pathway.
The Entner-Doudoroff pathway in some prokaryotes describes a series of reactions that catabolize glucose to pyruvate using a different set of enzymes from those used in either glycolysis or the pentose phosphate pathway.
Aldolase A
Aldolase A is an enzyme which catalyses one of the aldol reactions of glycolysis in which fructose 1,6-bisphosphate is broken down into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate.
Aldolase A is an enzyme which catalyses one of the aldol reactions of glycolysis in which fructose 1,6-bisphosphate is broken down into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate.
