Biochem 11.1 Glycolysis Quiz

Glucose is broken down into two pyruvate molecules, generating two ATP and two NADH.

Glycolysis is a metabolic pathway that occurs entirely in the cytoplasm of the cell.

The energy-investment phase refers to the first five steps of glycolysis, where energy is consumed to prepare glucose for further breakdown.

The first step of glycolysis is the irreversible phosphorylation of glucose to form glucose 6-phosphate.

Hexokinase is the enzyme that catalyzes the phosphorylation of glucose to glucose 6-phosphate in the first step of glycolysis.

The phosphorylation of glucose by ATP is highly exergonic and irreversible due to the energetic coupling to ATP hydrolysis.

The energy-investment phase of glycolysis involves the investment of ATP, which is converted to ADP. This sets the stage for energy production in the later steps.

The energy-investment phase prepares glucose for further breakdown, making its carbon skeleton more reactive and primed for energy release.

The first committed step of glycolysis, where fructose 6-phosphate is converted to fructose 1,6-bisphosphate.

The enzyme that catalyzes the committed step of glycolysis, converting fructose 6-phosphate to fructose 1,6-bisphosphate.

The process of breaking down glucose into pyruvate, generating ATP and NADH.

A six-carbon sugar that is the starting material for glycolysis; it is broken down into two molecules of pyruvate.

A three-carbon molecule produced in glycolysis, which serves as the starting point for the energy payoff phase.

An enzyme that catalyzes the cleavage of fructose 1,6-bisphosphate into two three-carbon molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (G3P).

An isomer of glyceraldehyde 3-phosphate, produced by the action of aldolase.

The enzyme that catalyzes the interconversion of dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (G3P).

The energy-payoff phase of glycolysis encompasses the last five steps, where energy is released from the fuel molecule, producing ATP and NADH.

Glyceraldehyde-3-phosphate (G3P) is a key intermediate in the energy-payoff phase. It is produced at the end of the energy-investment phase and undergoes further transformations to generate energy.

In step 6 of glycolysis (the first step of the energy-payoff phase), G3P is oxidized, and inorganic phosphate is added to form 1,3-bisphosphoglycerate. This reaction also reduces NAD+ to NADH, generating energy.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is the enzyme that catalyzes step 6 of glycolysis, the oxidation of G3P. It ensures the efficient transfer of electrons and phosphate.

The reduction of NAD+ to NADH in step 6 of glycolysis is important because NADH carries high-energy electrons that can be used to generate ATP later in the electron transport chain.

The energy-payoff phase produces more ATP than the investment phase due to the formation of 1,3-bisphosphoglycerate, which later contributes to the production of ATP.

The six steps of the energy-investment phase prepare glucose for the energy-payoff phase. By modifying the glucose structure, these steps set the stage for generating a net gain of ATP.

Each G3P molecule produced at the end of the energy-investment phase goes through the five steps of the energy-payoff phase, producing ATP and NADH. Since two G3P are produced, the yield for a single glucose is doubled.

A metabolic pathway that converts pyruvate to lactate, regenerating NAD+ for glycolysis.

The enzyme that catalyzes the conversion of pyruvate to lactate in lactic acid fermentation.

A metabolic pathway that converts pyruvate to ethanol and CO2, regenerating NAD+ for glycolysis.

The enzyme that catalyzes the decarboxylation of pyruvate to acetaldehyde in alcoholic fermentation.

The enzyme that catalyzes the reduction of acetaldehyde to ethanol in alcoholic fermentation.

A process where cells unable to perform respiration export lactate to be processed by well-oxygenated cells.

The ability of a substance to evaporate into the gas phase.

The ratio of products to reactants in a reversible reaction, indicating the direction of the reaction.

Pyruvate kinase is an enzyme that catalyzes the irreversible transfer of a phosphate group from phosphoenolpyruvate (PEP) to ADP, forming ATP. This reaction is the final step in glycolysis, where two ATP molecules are produced per glucose entering the pathway.

The energy-payoff phase of glycolysis uses the glyceraldehyde 3-phosphate (G3P) molecules from earlier stages and produces NADH and ATP. For each G3P, one NADH and two ATP are produced. Remember that two G3Ps are generated per glucose.

The net gain of ATP from glycolysis is only two ATP per glucose molecule because the energy-investment phase consumes two ATP. The energy-payoff phase yields four ATP, but two were used in the earlier steps.

The complete pathway of glycolysis results in the production of two pyruvate molecules, two ATP molecules, and two NADH molecules. This breakdown of glucose is essential for energy production in the cell.

The enzymes involved in glycolysis have specific names. Pyruvate kinase is named after the reverse reaction, even though it only works in the forward direction (glycolysis).

Three of the ten reactions in glycolysis are irreversible, meaning they can only proceed in one direction. These reactions are step 1 (hexokinase), step 3 (phosphofructokinase), and step 10 (pyruvate kinase).

The energy-investment phase prepares glucose for further breakdown by investing energy in the form of ATP. This sets the stage for the energy-payoff phase, where more ATP is generated. You can think of it as spending energy now to gain more later.

The energy-investment phase of glycolysis consists of the first five steps. These steps utilize ATP to modify glucose so it can be broken down further. In the end, glucose is converted to two glyceraldehyde 3-phosphate (G3P) molecules.

PFK-1 (phosphofructokinase-1) is the enzyme that catalyzes the third step of glycolysis, which is the irreversible conversion of fructose 6-phosphate to fructose 1,6-bisphosphate. This step is considered the commitment step of glycolysis, meaning that once it occurs, the pathway is committed to proceeding to generate pyruvate.

PFK-1 is highly regulated because it controls the flux of glucose through the glycolytic pathway, ensuring that glycolysis occurs only when needed and at the appropriate rate.

The catabolism of glucose through glycolysis generates a net yield of 2 ATP molecules per glucose molecule.

Mannose 6-phosphate is a sugar phosphate that is produced from the phosphorylation of mannose by hexokinase. It can then be converted to fructose 6-phosphate by phosphomannose isomerase, allowing it to enter the glycolytic pathway.

Phosphomannose isomerase catalyzes the isomerization of mannose 6-phosphate to fructose 6-phosphate, a crucial step in the metabolism of mannose.

Fructose 6-phosphate is a key intermediate in the glycolytic pathway. It can be produced from various sources, including glucose, mannose, and fructose. Therefore, it serves as a central hub for the metabolism of multiple sugars.

The catabolism of nonglucose monosaccharides, such as fructose and galactose, can enter the glycolytic pathway at different points, bypassing specific enzymes and potentially yielding different net ATP production.

The enzymes involved in the catabolism of nonglucose monosaccharides, like fructose and galactose, can be regulated differently compared to those in the classic glycolytic pathway, leading to variations in the overall control of glycolysis.