Glycolysis Learning Objectives

Insulin

A hormone released during the fed state that promotes the storage of fuels and synthesis of complex molecules, facilitating glucose uptake and glycogen synthesis.

Glucagon

A hormone released during the fasting state that maintains blood glucose levels by increasing glucose secretion from the liver.

Epinephrine

A short-term stress hormone that increases fuel availability in the blood by stimulating glycogenolysis in the liver and muscles.

Cortisol

A long-term stress hormone that promotes gluconeogenesis and protein breakdown to provide glucose.

GLUT4

A glucose transporter located in muscle and fat cells that mediates insulin-stimulated glucose uptake.

Hexokinase

An enzyme that catalyzes the phosphorylation of glucose, with a low Km and regulated by feedback inhibition from its product.

Glucokinase

An enzyme found in the liver and pancreatic β-cells that catalyzes the phosphorylation of glucose with a high Km and is induced by insulin.

Phosphofructokinase-1 (PFK-1)

A key regulatory enzyme in glycolysis that converts fructose-6-phosphate to fructose-1,6-bisphosphate and is allosterically regulated by ATP, AMP, and fructose-2,6-bisphosphate.

Aerobic Glycolysis

A metabolic pathway that converts glucose to pyruvate in the presence of oxygen, producing a large amount of ATP.

Anaerobic Glycolysis

A metabolic pathway that converts glucose to lactate (or ethanol) without oxygen, resulting in a lower yield of ATP.

PFK-1 Deficiency (Tarui Disease)

A condition characterized by exercise intolerance and muscle cramps due to impaired glycolysis, resulting from lack of PFK-1 activity.

GLUT-1 Deficiency

A disorder causing seizures and developmental delays due to impaired glucose transport into the brain.

Glucokinase Deficiency

A condition leading to maturity-onset diabetes of the young (MODY) due to reduced glucokinase activity and impaired insulin secretion.

Pyruvate Kinase Deficiency

A condition leading to hemolytic anemia due to reduced ATP production in red blood cells from lack of pyruvate kinase activity.

Citrate

A compound that inhibits PFK-1 in muscle to signal sufficient energy, but does not significantly inhibit PFK-1 in the liver.

Glycolysis Regulation in Liver vs Muscle

In the liver, glycolysis is regulated by blood glucose levels; in muscle, it is regulated by energy demand.

Energy Yield of Aerobic Glycolysis

Up to 38 ATP produced per glucose molecule in the presence of oxygen.

Energy Yield of Anaerobic Glycolysis

Only 2 ATP produced per glucose molecule without oxygen.