Glycolysis Pathway | Enzymes, Regulation and Products

Summary

This lesson on glycolysis explains the process of glucose breakdown in the cytosol of cells, highlighting its importance for ATP production, particularly in oxygen-depleted conditions and in red blood cells. The ten-step pathway features three irreversible enzymatic reactions and is divided into two stages: energy consumption and energy acquisition. Key enzymes such as hexokinase, phosphofructokinase-1, and pyruvate kinase are emphasized for their regulatory roles. The lesson concludes with the net production of 2 ATP, 2 NADH, and 2 pyruvate molecules, underscoring glycolysis's vital role in cellular metabolism.

Takeaways

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Q & A

What is glycolysis?

Glycolysis is the metabolic pathway that breaks down glucose into pyruvate, occurring in the cytosol of a cell, and does not require oxygen.

What are the two stages of glycolysis?

The two stages of glycolysis are the consumption stage, where ATP is used, and the acquisition stage, where ATP is produced.

What role does hexokinase play in glycolysis?

Hexokinase phosphorylates glucose to form glucose-6-phosphate using ATP, trapping glucose within the cell.

How is phosphofructokinase-1 (PFK-1) regulated?

PFK-1 is negatively regulated by ATP and citrate, indicating sufficient energy levels, and positively regulated by AMP and fructose-2,6-bisphosphate, indicating energy deprivation.

Why is the reaction catalyzed by pyruvate kinase considered irreversible?

The reaction is irreversible because it commits the product (pyruvate) to further processing, and is tightly regulated by fructose-1,6-bisphosphate and inhibited by ATP.

What is the significance of fructose-2,6-bisphosphate in glycolysis?

Fructose-2,6-bisphosphate is a potent activator of PFK-1, allowing glycolysis to proceed even when ATP levels are high, thus playing a crucial role in metabolic regulation.

What happens during the conversion of fructose-1,6-bisphosphate in glycolysis?

Fructose-1,6-bisphosphate is cleaved by aldolase into two 3-carbon molecules: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.

What are the products of glycolysis?

The main products of glycolysis are 2 pyruvate molecules, 2 ATP, and 2 NADH.

What is the net equation for glycolysis?

The net equation for glycolysis is: 1 glucose + 2 inorganic phosphate + 2 ADP + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH + 2 H+.

How does the body utilize NADH produced in glycolysis?

NADH can be sent to the mitochondria to be processed through the electron transport chain for more ATP production or can be converted back to NAD+ for glycolysis to continue.