Test questions for week 5 (lab)

Pyruvate is the final product of aerob glycolysis! Why does anaerobe glycolysis result in lactate?
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Pyruvate is the final product of aerob glycolysis! Why does anaerobe glycolysis result in lactate?
We need to regenerate NAD+ to be used again in the glycolysis. This is normally done through oxidative phosphorylation. As this process requires oxygen, it is done instead by producing lactate from pyruvate at the end step of anaerobe glycolysis. This reaction is catalysed by the lactate dehydrogenase enzyme.
The net ATP-production of glycolysis is 2 ATP (per glucose molecule)! How can this happen when in the "preparatory phase" as well as in the "payoff" phase, 2 kinases consume (preparatory phase) and produce (payoff phase) ATP? Why isn't the net sum of ATP 0?
In the preperatory phase, 1 ATP is consumed by hexokinase, and 1 by PFK-1 which is 2 in total. In the payoff phase, ATP is reproduced again, 1 by phosphoglycerate kinase and 1 by pyruvate kinase. These final reactions however will occur twice, as two molecules of the reactants are produced from a single glucose molecule.
This is all made possible since in the oxidative step of the glycolysis phosphoglycerate is phosporylated without ATP. Inorganic phosphate is used instead. Therefore we will have an additional phosphate-group for the later kinase reaction(s).

Therefore, the net ATP of glycolysis will be -1+(-1) + (1 2) + (1 2) = 2
Red blood cells in the lungs are sufficiently oxygenated to carry out aerobe glycolysis! Why do they, however, metabolize glucose to lactate?
Because erythrocytes lack mitochondria, they also lack the oxidative enzymes that are required for aerobic respiration. They follow the Embden-Meyerhof pathway instead.
Write the glycolytic reaction with structures, in which inorganic phosphate will incorporate.
Glyceraldehyde-3-phosphate dehydrogenase
Image: Write the glycolytic reaction with structures, in which inorganic phosphate will incorporate.
Write the glycolytic reaction with structures, in which NADH is produced.
Glyceraldehyde-3-phosphate dehydrogenase
Image: Write the glycolytic reaction with structures, in which NADH is produced.
Name the irreversible kinase reactions of glycolysis.
Hexokinase, pfk-1, pyruvate kinase
Why is arsenate toxic (way of action, enzyme)?
Arsenate can replace inorganic phosphate in the step of glycolysis that produces 1,3-bisphosphoglycerate from glyceraldehyde 3-phosphate. This yields 1-arseno-3-phosphoglycerate instead, which is unstable and quickly hydrolyzes, forming the next intermediate in the pathway, 3-phosphoglycerate. Therefore, glycolysis proceeds, but the ATP molecule that would be generated from 1,3-bisphosphoglycerate is lost.

As with other arsenic compounds, arsenite binds to lipoic acids, inhibiting pyruvate dehydrogenase complex, blocking the Krebs cycle and therefore resulting in further loss of ATP. Also inhbits α-ketoglutarate dehydrogenase complex.
Does arsenate inhibit gluconeogenesis? Why?
Arsenate inhibts the production of acetyl-CoA from pyruvate (pyruvate dehydrogenase complex), which allosterically activates pyruvate carboxylase. Therefore, when no acetyl-CoA is produced to activate the enzyme, gluconeogenesis can not take place.
Why is monoiodoacetate capable to inhibit glyceraldehyde-3-phosphate dehydrogenase?
The essential cysteine residue in the active center of GAPDH forms a thioether bond with IA and can therefore not react anymore with the physiological substrate glyceraldehyde-3-phosphate. As a consequence, GAPDH is inactivated after exposure to IA and glycolysis is inhibited.
Write with structures the reaction catalyzed by hexokinase.
Image: Write with structures the reaction catalyzed by hexokinase.
Write with structures the reaction catalyzed by phosphofructokinase-1.Write with structuresthe reaction catalyzed by phosphohexose isomerase.Write with structures the reaction catalyzed by phosphofructokinase-2.Write with structures the reaction catalyzed by aldolase.Write with structures the reaction catalyzed by triose phosphate isomerase.Write with structures the reaction catalyzed by phosphoglycerate kinase.Write with structures the reaction catalyzed by phosphoglycerate mutase.Write with structures the reaction catalyzed by pyruvate kinase.Write with structures the reaction catalyzed by lactate dehydrogenase.Write with structures the reaction catalyzed by pyruvate decarboxylase.Write with structures the reaction catalyzed by alcohol dehydrogenase.Write with structures the reaction catalyzed by fructokinase.Write with structures the reaction catalyzed by fructose 1-phosphate aldolase.Write with structures the reaction catalyzed by galactokinase.