(FC) Regulation of Glycolysis to Shuttle Mechanism

Isozyme

Variant forms of an enzyme that catalyze the same reaction but differ in amino acid sequence and are expressed in different tissues.

Allosteric enzyme

Enzyme that changes activity due to the binding of effector molecules, can be activated or inhibited by intermediates.

Fructose-1,6-bisphosphate (FBP)

An important allosteric activator for pyruvate kinase and inhibitor for phosphofructokinase.

Glucokinase

A specific type of hexokinase found in the liver that is specific for glucose and has different regulatory properties.

Protein kinase

Enzyme produced in the liver when blood glucose levels are low, inhibits pyruvate kinase to stop glycolysis.

Hormonal Regulation

Insulin and somatostatin lower blood glucose levels, while glucagon, epinephrine, cortisol, ACTH, growth hormone, and thyroxine increase it.

ATP's Role in Glycolysis

ATP acts as an inhibitor for several key enzymes in glycolysis when energy levels are sufficient.

Covalent modification

A process by which the activity of an enzyme is regulated through the addition or removal of chemical groups.

Feedback inhibition

A regulatory mechanism whereby the end product of a pathway inhibits an earlier step to modulate activity.

Substrate-level phosphorylation

A direct method of synthesizing ATP by transferring a phosphate group from a substrate to ADP.

Glycogenolysis

The biochemical process of breaking down glycogen into glucose-1-phosphate, which can enter glycolysis.

Pyruvate

The end product of glycolysis that can be further metabolized into acetyl-CoA for the Krebs cycle or converted to lactate.

NAD+ in glycolysis

A coenzyme that acts as an electron carrier in glycolysis, essential for the oxidation of glyceraldehyde-3-phosphate.

Hormonal effects on metabolism

Hormones can significantly influence metabolic pathways by changing enzyme activity or gene expression.

Cori Cycle

The cycle in which lactate produced during anaerobic glycolysis in muscles is transported to the liver and converted back to glucose.

Gluconeogenesis

The metabolic process by which glucose is synthesized from non-carbohydrate precursors, primarily in the liver.

Hexokinase

An enzyme that catalyzes the phosphorylation of glucose to glucose-6-phosphate in glycolysis.

Lactate dehydrogenase

An enzyme that catalyzes the conversion of pyruvate to lactate when oxygen is low, helping regenerate NAD+.

Pyruvate kinase regulation

Regulated by fructose-1,6-bisphosphate, which activates it, and by ATP, which inhibits it.

Insulin's role in glycolysis

Insulin promotes the uptake of glucose by cells and enhances glycolytic enzyme activity.

Glycogenesis

The process of converting glucose to glycogen for storage, primarily in the liver and muscles.

Acetyl-CoA

A key intermediate in metabolism, formed from pyruvate, entering the Krebs cycle for energy production.

Aerobic respiration

A metabolic process that requires oxygen to produce ATP from glucose.

Anaerobic glycolysis

The process of converting glucose to lactate when oxygen is scarce, generating ATP without oxygen.

Krebs Cycle (Citric Acid Cycle)

A series of enzymatic reactions in the mitochondria that generates ATP and electron carriers from acetyl-CoA.

Oxidative phosphorylation

The final stage of cellular respiration where ATP is produced in the mitochondria using electron transport chains.

FADH2

A coenzyme that serves as an electron carrier in the Krebs cycle and oxidative phosphorylation.

Glycolytic pathway

The sequence of reactions converting glucose into pyruvate, generating ATP and NADH.

Insulin's effect on glycogenolysis

Insulin inhibits glycogenolysis, promoting glucose storage instead of release.

Fructose-2,6-bisphosphate

A potent allosteric regulator of phosphofructokinase that increases glycolytic flux.

Liver's role in glucose homeostasis

The liver regulates blood glucose levels through glycogen storage, gluconeogenesis, and glycogenolysis.

Chrelin

A hormone that stimulates appetite and may influence energy metabolism.

Uptake of glucose into cells

Facilitated by transport proteins such as GLUT transporters, especially in response to insulin.

Regulation of pyruvate dehydrogenase

Controlled by the availability of substrates and the energy status of the cell.

Energetics of glycolysis

Glycolysis produces a net gain of 2 ATP and 2 NADH per molecule of glucose.

Pentose phosphate pathway

An alternative glucose metabolic pathway that generates NADPH and ribose for biosynthesis.

Liver and metabolic syndrome

The liver's metabolic responses contribute significantly to conditions like insulin resistance and fatty liver disease.

Role of hormones in energy balance

Hormones like insulin, glucagon, and leptin regulate energy intake and expenditure.

High-intensity exercise and glycolysis

During high-intensity exercise, glycolysis predominates to rapidly supply ATP under anaerobic conditions.

Glycolysis

The metabolic pathway that converts glucose into pyruvate, yielding energy in the form of ATP and NADH.

Glucose-6-phosphate

A product of the phosphorylation of glucose, it can enter glycolysis or be used in other metabolic pathways.

Glycogen

A stored form of glucose primarily found in the liver and muscles, used during fasting or intense exercise.

Adenosine triphosphate (ATP)

The primary energy carrier in all living organisms, produced during glycolysis and cellular respiration.

Phosphofructokinase (PFK)

A key regulatory enzyme in glycolysis that converts fructose-6-phosphate to fructose-1,6-bisphosphate.

Pyridoxal phosphate

A coenzyme involved in amino acid metabolism and plays a role in regulating glycolysis.

Liver gluconeogenesis

The process through which the liver synthesizes glucose from non-carbohydrate sources mainly during fasting.

Dehydrogenase

An enzyme that catalyzes the removal of hydrogen from a substrate, important in metabolic pathways.

Insulin secretion

Release of insulin from the pancreas in response to high blood glucose levels, promoting glucose uptake.

Energy investment phase

The initial stage of glycolysis where ATP is consumed to activate glucose for breakdown.

Energy recovery phase

The culmination of glycolysis where ATP and NADH are produced after the cleavage of glucose.

Acidosis

A condition resulting from increased lactate production during anaerobic glycolysis, often leading to metabolic complications.

Mitochondria

Organelles responsible for energy production through oxidative phosphorylation and the Krebs cycle.

Futile cycle

A situation where two metabolic pathways run simultaneously, consuming energy without producing net gain.

Hormonal cascade

A series of hormone actions that lead to a physiological effect, particularly in glucose metabolism.