Chapter 8 Glycolysis (slide notes) Flashcards
is glycolysis anabolic or catabolic process?
Trick question. it is both. ergo it is AMPHIBOLIC
glycolysis converts one molecule of glucose to ___ molecules of pyruvate with the generation of ____ molecules of atp
2 molecules of pyruvate
2molecules of ATP
break down the general two steps of glycolysis
stage 1. traps glucose in the cell and modifies it so that it can be cleaved into a pair of phosphorylated 3-carbon compount
- oxidizes the 3 carbon compounds to pyruvate while generating 2 molecules of ATP
what enzyme traps glucose in the cell and begins glycolysis
hexokinase
upon entering the cell through a specific transport protein, glucose is phosphorylated at the expense of ATP to form glucose-6-phosphate
hexokinase, which requires Mg+2 or Mn+2 as a cofactor, catalyzes the reaction
glucose 6 phosphate cannot pass through the membrane to the extracellular side
addition of phosphoryl group facilitates metabolism
hexokinase, like most kinases, emplay substrate-binding ______ to minimize hydrolysis of ATP
substrate binding induced fit
the conversion of glucose 6-phosphate to fructose 6-phosphate is catalyzed by __________ the reaction is readily _______-
phosphoglucose isomerase
the reaction is readily reversible
frutose 1,6 bisphosphate is generated from glucose 6 phosphate. this reaction is catalyzed by the ______ enzyme ____________-
allosteric enzyme. phosphofructokinase (PFK)
the six carbon sugar is cleaved into two three carbon fragments. where the delta G is
+23.8
dihydroxyacetone phosphate to glyceraldehyde 3-phosphate uses what enzyme
triose phosphate isomerase
Glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate uses what enzyme
glceraldehyde 3-phosphate dehydrogenase
coupling through ______ intermediate can lower activation energy
thioester
1,3-bisphosphoglycerate to 3 phosphoglycerate uses what enzyme?
phosphoglycerate kinase. (removes phosphate)
why does PEP phosphenolpyruvate have such a high phosphoryl-transfer potential?
tautomerization. phosphoryl group traps pyruvate in an unstable enol form. when transfer of phosphoryl group is complete, enol converts to more stable ketone (pyruvate)
`what are the 2 irreversible reactions of glycolysis?
hexokinase
phosphofructokinase-1 (PKF-1)
pyruvate kinase
fermentations are ATP-generating pathways in which electrons are removed from one organic compound and passed to another organic compound. the formation of ethanol from pyruvate regenerates _______. pyruvate carboxylase requires the vitamam ________
regenerates NAD+
requires vitamen thiamine B1
the conversion of glucose into two molecules of ethanol is called ___________
alcoholic fermentation
the NADH generated by glyceraldehyde 3-phosphate dehydrogenase is oxidized by alcohol dehydrogenase, generating NAD+
the converstion of glucose into 2 molecules of lactate is called ____________-
lactic acid fermentation
in the liver, fructose is metabolized by the ______ pathyway
fructose-1-phosphate
in other tissues, such as adipose tissue, fructose is directly phosphorylated by _______
hexokinase
galactose-glucose conversion pathway begins with the phosphorylation of galactose by __________-
galactokinase
glucose 1-phosphate can be converted into glucose 6- phosphate by __________–
phosphoglucomuctase
lactose intolerance or hypolactasia occurs because ___________
most adults lack the enzyme to degrade lactose
enzymes catalyzing irreversible reaction in the metabolic pathway are potential CONTROL SITES
in glycolysis, these enzymes are ___,____,____
hexokinase, phosphofructokinase, and pyruvate kinase
_________________ is the key regulator of glycolysis in mammals. the enzyme is allosterically ________ by ATP and allosterically ______ by AMP
(reverse process) when ATP needs are great, _______ generates ATP from 2 ADP. AMP then becomes the signal for low energy state
inhibited by ATP and allosterically stimulated by AMP
adenylated kinase
_________, released by pancreatic alpha cells when blood sugar is low, actives the phosphatase fuction of PFK-2
glucagon…. this is hormonal regulation
also glucagon is then acting as a positive regulator for activation of PK2 therfore reducing the level of fructose 2,6, bisphospate
???? inconsistant
______ released by pancreatic beta cells when blood glucose levels are high. the effects of this substance on glycolysis include activation of the kinase function PFK-2 which increases levels of fructose 2,6-bispohophate in the cell, in turn increasing glycolytic flux.
???? inconsistant
hexokinase is allosterically _________
inhibited by glucose 6-phosphate
pyruvate kinase is __________ and ________ stimulated by fructose 1-,6 bisphosphate the product of phosphofructokinase reaction
pyruvate kinase is inhibited by the allosteric signals ATP and alanine, and stimulated by fructose 1, 6- bisphosphate, the product of phosphofrcutokinase reaction
in the muscle, _______ is regulated to meet the energy needs of contraction
glycolysis
the key regulators of phosphofructokinase in liver are citrate which reports on the status of the citric acid cycle, and ___________
fructose 2,6- bisphosphate
citrate inhibits phosphofructokinase while fructose 2,6 bisphosphate is a powerful activator
__________ is a form of the hexokinase found in hepatocytes. the high Km of glucokinase for glucose means that this enzyme is saturated only at very high concentrations of substrate.
glucokinase
glucokinase is active only after a meal, when blood glucose levels are high, this feature of hepatic glucokinase allows the liver to buffer blood glucose
radpidly growing tumors obain ATP by metabolizing glucose to lactate even in presence of oxygen. a process termed aerobic glycolysis or the __________
Warburg effect
the transcription factor hypoxia-inducible transcription factor 1 (HIF-1) faciliates aerobic glycolysis. exercise training also timulates HIF-1 which enhances the ability to generate ATP anaerobically and stimulate new blood vessel growth
general slide
Insulin!
Insulin is secreted by β cells of the pancreas in response to high blood levels of glucose. This secretion is stimulated by the metabolism of glucose by the β cells.
Glucose enters β cells through GLUT2 and is metabolized to pyruvate, and the pyruvate is subsequently oxidized to CO2 and H2O.
The increase in ATP closes a K+ channel, which alters the charge across the cell membrane. This alteration in turn opens Ca2+ channels. The influx of Ca2+ ions stimulates the release of insulin.
