Other Glycolysis Concepts - Biochemistry

Gluconeogenesis does not convert glucose into pyruvate, rather it builds glucose from non-carbohydrate organic compounds. All of the other answer choices are possible fates of glucose once it enters the cell.

Phosphofructokinase catalyzes the most regulated step of glycolysis and limits the reaction rate of glycolysis. Glucose is converted to pyruvate during glycolysis, not lactate, which is the case in some organisms (humans) through the process of fermentation. Glucokinase, not hexokinase is found in the liver, fructose-2,6-bisphosphate activates, not inhibits phosphofructokinase.

An epimerase inverts the stereochemistry at a particular carbon, but it cannot add additional carbons. While hexokinase can phosphorylate fructose into a glycolytic intermediate in most tissue, the liver does not contain any hexokinase. In the liver, fructose is phosphorylated by fructokinase into fructose-1-phosphate. This is cleaved by an aldolase to form dihydroxyacetone phosphate (DHAP), a glycolytic intermediate, and glyceraldehyde, a precursor to glyceraldehyde-3-phosphate (G3P), another glycolytic intermediate. Glyceraldehyde can either be phosphorylated into G3P or be used to promote fat storage.

This is a slightly misleading question. Glycolysis is an anaerobic process. Its products are always 2 pyruvate, 2 NADH, and 2 ATP. The fate of the pyruvate depends on the absence and/or presence of oxygen, in which it will be reduced into lactate or cleaved into acetyl-CoA to enter the Krebs cycle, respectively.

If molecular oxygen is present, the products of glycolysis will continue and be fed into aerobic metabolism: the citric acid cycle and oxidative phosphorylation. If molecular oxygen is absent, glycolysis will lead to anaerobic metabolism/fermentation. Thus, the fate of pyruvate depends on the availability of oxygen. does need to be recycled for glycolysis to proceed, but this can happen via the electron transport, which can only proceed if oxygen is present. Thus, while this is fundamentally correct, it is a downstream regulator. Coenzyme A is not a limiting factor in the fate of pyruvate, but it does get added after a molecule of carbon dioxide is released, producing acetyl-CoA during pyruvate dehydrogenation. Phosphoric acid and calcium ions are not relevant to this question.

Glucose can be catabolized by both aerobic and anaerobic means. When glucose undergoes oxidative phosphorylation (aerobic metabolism), the end products are carbon dioxide, water, and ATP. In the absence of oxygen, glucose can undergo either lactic acid or alcoholic fermentation. Lactate is a result of lactic acid fermentation, and ethanol and carbon dioxide are results of alcoholic fermentation.

Glucose goes through glycolysis to form pyruvate molecules which then proceed into the pyruvate dehydrogenase complex. Acetyl-CoA is created from this, which can then move into the citric acid cycle. High energy electron carries, and , that were created in glycolysis and the citric acid cycle finally go through the electron transport chain to pump hydrogens through the mitochondrial membrane. These hydrogens are used to generate ATP via the ATP synthase.

If a cell is lacking in oxaloacetate, the Krebs cycle will be unable to continue. Therefore, there will be no way for the electron transport chain to receive the high energy electrons it requires to create ATP. And so, fermentation will take over in the cell for creation of ATP. Glycolysis will not stop, but the end product pyruvate will build up because it will only be able to be used for fermentation, not in the pyruvate dehydrogenase complex.

In glycolysis, glucose is broken down. 2 ATP are required for glycolysis to begin, resulting in a creation of 4 ATP. This is a net of 2 ATP. NADH is created from , not the other way around. While 7 of the 10 steps of glycolysis are reversible, the other 3 are irreversible. Finally, if ATP is plentiful, there is no need for glycolysis to speed up (it will actually likely slow down).

In glycolysis, glucose is oxidized, and the final products are 2 pyruvate, 2 ATP, and 2 NADH. The first step is irreversible, and is the conversion of glucose to glucose-6-phosphate by the enzyme hexokinase. The only remaining answer choice is "every step is irreversible." That statement is false. Steps 1,3, and 10 are irreversible, but the remaining steps are reversible.

Glycolysis is the only of the above choices that occurs in the cytoplasm. The remaining occur in different parts of the mitochondria. The Krebs cycle occurs in the mitochondrial matrix. Both oxidative phosphorylation and the electron transport chain occur along the inner mitochondrial membrane.

in unrelated to the Krebs cycle and the electron transport chain. is produced during the pentose phosphate pathway, which is a branch off of glycolysis. The first phase of the pentose phosphate pathway is called the oxidative phase, and is where is created. During the second phase, five-carbon sugars are created, the most important being ribose-5-phosphate.

NADPH is a molecule created during the oxidative phase of the pentose phosphate pathway. It is used in anabolic reactions, specifically in the formation of fatty acids. Another important role is that it acts as an anti-oxidant. Finally, NADPH is easily discriminated from NADH in the body because of an additional attached phosphate group. This allows the body to regulate the concentrations of the two similar molecules independently.

A dehydrogenase is an enzyme that removes hydrogen ions from a molecule, thereby oxidizing it.Lactate dehydrogenase converts lactate to pyruvic acid and NADH to NAD+ in glycolysis.The reaction is reversible, in which case it provides pyruvate for gluconeogenesis.Lactate dehydrogenase is present in most tissues with some isoforms more frequent than others. For example, isoenzyme LDH-1 is found in the heart, red blood cells, and brain.

Fructose is mainly metabolized by the liver from sugar, honey and fruits. Fructose can be converted to fructose-1-phosphate and then to dihydroxyacetone phosphate (DHAP) and glyceraldehyde.

Glycolysis is a process that takes place via ten reactions, involving the activity of multiple enzymes and occurs in the cytoplasm of the cell in two distinct phases: an energy consumption phase and an energy production phase. The first step in glycolysis is the conversion of glucose to glucose-6-phosphate through the consumption on one ATP molecule. Glucose is reacted upon by the enzyme hexokinase to carry out this step. Kinases are a group of enzymes that add phosphate groups by removing them from an ATP. In the second step, glucose-6-phosphate is then reacted upon by phosphoglucose isomerase. Isomerases are a group of enzymes that rearranged the structure of a molecule without changing the molecular formula. In this case the phosphoglucose isomerase rearranges the glucose-6-phosphate into fructose-6-phosphate. The third step involves another kinase: phosphofructokinase-1. This enzyme attached another phosphate group to fructose-6-phosphate, creating fructose-1,6-bisphosphate. In the fourth step, this molecule is then reacted upon by fructose bisphosphate aldolase. An aldolase is an enzyme that creates or breaks carbon-carbon bonds. This step results in the creation of two molecules: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. The fifth step involves another isomerase, triose phosphate isomerase, which converts the dihydroxyacetone into glyceraldehyde-3-phosphate (G3P).The sixth step involves the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). GAPDH moves a hydrogen onto the electron acceptor . A phosphate group from inorganic phosphate instead of ATP replaces the hydride group that was taken from G3P. This creates the molecule 1,3 bisphosphoglycerate. The seventh reaction involves yet another kinase, phosphoglycerate kinase. Kinases can also take phosphate groups away. During this step, two phosphate groups are transferred from the 1,3 Bisphosphoglycerate molecules onto 2 molecules of ADP to create two molecule of ATP. The 1,3 Bisphosphoglycerate then becomes 3-phosphoglycerate. The eighth reaction involves the enzyme phosphoglycerate mutase which is essentially another isomerase. It converts 3-phosphoglycerate to 2-phosphoglycerate. The ninth reaction involves the enzyme enolase which produces a double bond by removing the hydroxyl group on 2-phosphoglycerate which results in phosphoenolpyruvate (PEP). The tenth and final reaction of glycolysis involves the enzyme pyruvate kinase. Just like the previous kinase reaction, this kinase is going to remove phosphate groups from the molecule to produce 2 molecules of ATP (one per molecule of PEP created from 1 molecule of glucose. The final product of glycolysis is pyruvate.

Gluconeogenesis does not convert glucose into pyruvate, rather it builds glucose from non-carbohydrate organic compounds. All of the other answer choices are possible fates of glucose once it enters the cell.

Phosphofructokinase catalyzes the most regulated step of glycolysis and limits the reaction rate of glycolysis. Glucose is converted to pyruvate during glycolysis, not lactate, which is the case in some organisms (humans) through the process of fermentation. Glucokinase, not hexokinase is found in the liver, fructose-2,6-bisphosphate activates, not inhibits phosphofructokinase.

An epimerase inverts the stereochemistry at a particular carbon, but it cannot add additional carbons. While hexokinase can phosphorylate fructose into a glycolytic intermediate in most tissue, the liver does not contain any hexokinase. In the liver, fructose is phosphorylated by fructokinase into fructose-1-phosphate. This is cleaved by an aldolase to form dihydroxyacetone phosphate (DHAP), a glycolytic intermediate, and glyceraldehyde, a precursor to glyceraldehyde-3-phosphate (G3P), another glycolytic intermediate. Glyceraldehyde can either be phosphorylated into G3P or be used to promote fat storage.