Chapter 16. Glycolysis and Gluconeogenesis Flashcards
An ATP-generating process in which organic compounds act as both donors and acceptors of electrons; fermentations can take place in the absence of oxygen.
Fermentation
the conversion of glucose into ethanol with a concomitant production of ATP.
Alcoholic fermentation
the anaerobic metabolism of glucose to yield lactic acid with the concomitant production of ATP.
Lactic acid fermentation
The first irreversible step in a metabolic pathway under physiologic conditions; this step is catalyzed by an allosteric enzyme and commits the product to a particular chemical fate.
Committed step
the synthesis of glucose from noncarbohydrate precursors, including lactate, glycerol and amino acids.
Gluconeogenesis
a hydrolytic enzyme that converts glucose 6-phosphate to free glucose for release into the blood; it is located in the liver and kidney.
Glucose 6-phosphatase
a vitamin that plays a role in carboxylation and decarboxylation reactions.
Biotin
an enzyme with two different, often opposing, catalytic activities on one polypeptide chain. For instance, phosphofructokinase 2 synthesizes fructose 2,6-bisphosphate and fructose 2,6-bisphosphatase hydrolyzes it, yet both active sites are on the same polypeptide chain.
Bifunctional enzyme
activation of an allosteric enzyme in the latter section of a pathway by the product of a reaction that occurs earlier in the reaction pathway.
Feedforward stimulation
An organism that metabolizes glucose aerobically when oxygen is present and performs fermentation when oxygen is absent.
facultative anaerobe
A specialized isozyme of hexokinase which has a high KM for glucose and is not inhibited by glucose 6-phosphate.
glucokinase
The use of lactic acid fermentation to generate ATP even the presence of enough oxygen to support cellular respiration.
Aerobic glycolysis
a cyclic metabolic pathway in which lactate from active muscle is converted into glucose by the liver, which in turn supplies newly synthesized glucose to muscle and other tissues.
Cori cycle
An allosteric enzyme that catalyzes the formation of fructose 6-phosphate and participates in the regulation of gluconeogenesis.
fructose 1, 6-bisphosphatase
a kinase that phosphorylates fructose 6-phosphate to fructose 1,6-bisphosphate. Phosphofructokinase, an allosteric enzyme, is the major control point for flux through the glycolytic pathway.
phosphofructokinase (PFK)
formation of ATP from ADP in which the phosphate donor is a substrate with high-phosphoryl transfer potential.
Substrate-level phosphorylation
a sequence of reactions that convert glucose into pyruvate with a concomitant generation of energy.
Glycolysis
an enzyme that catalyzes the attachment of a phosphoryl group to a substrate, using ATP as a phosphoryl donor.
Kinase
a kinase that phosphorylates six carbon sugars, usually glucose, at the expense of ATP.
Hexokinase
organisms that cannot survive in the presence of oxygen and thus are usually dependent on fermentation as an source of cellular energy.
Obligate anaerobe
A key regulatory enzyme in glycolysis that catalyzes the formation of ATP and pyruvate from phosphoenolpyruvate and ADP.
Pyruvate kinase
An ester in which the noncarbonyl oxygen atom is replaced by a sulfur atom; thioesters are energy-rich intermediates in a number of biochemical reactions.
Thioester intermediate
A common nucleotide-binding domain in proteins that is made up of four α helices and a sheet of six parallel α strands.
Rossman fold
A pair of thermodynamically irreversible biochemical reactions that simultaneously produce and consume a pair of metabolic intermediates; these paired pathways may amplify metabolic signals and in some cases can also generate heat for the maintenance of temperature in tissues. Also called futile cycle.
Substrate cycle
Simultaneously decarboxylates and phosphorylates oxaloacetate to generate phosphoenolpyruvate.
phosphoenolypyruvate carboxykinase
a biotin-dependent enzyme that catalyzes the formation of oxaloacetate from pyruvate and CO2 at the expense of ATP. Pyruvate carboxylase is important in gluconeogenesis as well as for replenishment of the citric acid cycle.
Pyruvate carboxylase
