Metabolism and AMP Regulation in Exercise

In skeletal muscle, glucose 6-phosphate is a key substrate for glycolysis, a pathway that generates ATP.

In the liver, glucose 6-phosphate is converted to glucose by glucose 6-phosphatase, an enzyme located in the ER lumen.

Glucose 6-phosphatase is an enzyme responsible for the conversion of glucose 6-phosphate to glucose.

Glycogenolysis is the breakdown of glycogen into glucose, releasing glucose into the bloodstream.

The ER (Endoplasmic Reticulum) is an organelle involved in protein synthesis and lipid metabolism.

The ER lumen is the space inside the ER, where glucose 6-phosphatase is located.

A futile cycle occurs when two metabolic pathways work against each other, consuming energy without a net gain.

Glycolysis is a metabolic pathway that breaks down glucose to generate ATP.

Glycogen storage disease (GSD) is a group of genetic disorders that impair glycogen metabolism.

Type Ia (von Gierke) GSD is caused by a deficiency of glucose 6-phosphatase, leading to an accumulation of glycogen in the liver.

Type Ib GSD is caused by a deficiency of the microsomal glucose 6-phosphate translocase, impairing glucose 6-phosphate transport from the cytosol to the ER lumen.

Type II (Pompe) GSD is caused by a deficiency of lysosomal glucosidase, affecting glycogen breakdown in muscles.

Type IIIa (Cori or Forbes) GSD is caused by a deficiency of the debranching enzyme, impacting glycogen breakdown in both liver and muscle.

Type V (McArdle) GSD is caused by a deficiency of muscle phosphorylase, impairing glycogen breakdown in skeletal muscle.

Type VI (Hers) GSD is caused by a deficiency of liver phosphorylase, impacting glycogen breakdown in the liver.

Sugar nucleotides are suitable for biosynthetic reactions because their formation is irreversible, the nucleotide moiety interacts with enzymes, the nucleotidyl group facilitates nucleophilic attack, and tagging with nucleotidyl groups distinguishes hexoses.

The hydrolysis of PPi drives the forward reaction by removing the product and having a large negative free-energy change.

Glucose 6-phosphate is a starting point for glycogen synthesis. It can be formed by hexokinase from glucose or by gluconeogenesis from lactate.

Phosphoglucomutase converts glucose 6-phosphate to glucose 1-phosphate, which is then used in the next step of glycogen synthesis.

UDP-glucose pyrophosphorylase is a key enzyme in glycogen biosynthesis. It converts glucose 1-phosphate to UDP-glucose, which is a activated form of glucose.

UDP-glucose pyrophosphorylase catalyzes the irreversible conversion of glucose 1-phosphate and UTP to UDP-glucose and PPi.

The activation of glucose involves the attachment of uridine diphosphate (UDP) to glucose 1-phosphate. This forms UDP-glucose, which is then used for glycogen synthesis.

UTP (uridine triphosphate) is required for glycogen synthesis. It is used to synthesize UDP-glucose, the activated form of glucose used in glycogen synthesis.

An enzyme that catalyzes the transfer of a glucose residue from UDP-glucose to a nonreducing end of a branched glycogen molecule, forming an (α1⟶4) linkage.

An enzyme that catalyzes the formation of the (α1⟶6) bonds found at the branch points of glycogen. This branching is essential for glycogen's structure and function.

Glycogen synthesis requires a protein primer to initiate the process, and glucose molecules are activated as sugar nucleotides before being added to the growing chains.

The protein primer on which new glycogen chains are assembled. It is also the enzyme that catalyzes the initial assembly of the glycogen chain.

The autocatalytic formation of a glycosidic bond between the glucose of UDP-glucose and Tyr194 of glycogenin, and the addition of seven more glucose residues to form a primer that can be acted on by glycogen synthase.

Glycogenesis begins with the reactions of glycogenin, which is the primer for glycogen synthesis.

The balance between glycogen synthesis and breakdown is crucial for maintaining cellular and organismal homeostasis.

Epinephrine, glucagon, and insulin play key roles in regulating the balance between glycogen synthesis and breakdown.

The process where an enzyme activates another enzyme, which in turn activates another, creating a chain reaction.

The active form of glycogen phosphorylase, readily breaking down glycogen.

The less active form of glycogen phosphorylase, requiring activation.

Hormones like epinephrine and glucagon trigger the conversion of glycogen phosphorylase b to the active form, phosphorylase a.

A molecule that binds to a protein at a site other than the active site and influences the protein's activity.

A molecule that binds to a protein and increases its activity.

Calcium ions (Ca2+) and AMP are allosteric activators of glycogen phosphorylase in muscle, increasing its breakdown of glycogen.

Protein kinase A (PKA), activated by cAMP, phosphorylates phosphorylase kinase, leading to the activation of glycogen phosphorylase and increased blood glucose.

A mechanism where a molecule binds to a site on an enzyme that is not the active site, influencing the enzyme's activity.

The enzyme that removes phosphate groups from phosphorylase a, converting it to the less active form, phosphorylase b.

The active form of glycogen phosphorylase, stimulated by phosphorylation.

The less active form of glycogen phosphorylase.

The enzyme that activates phosphorylase b by adding a phosphate group.

A state of equilibrium in a cell or organism, maintained by regulatory mechanisms.

AMP levels increase in response to strenuous physical activity, signaling a need for energy production. This activates catabolic pathways for both carbohydrates and fatty acids, ensuring sufficient energy supply.

High AMP levels stimulate the breakdown of carbohydrates and fatty acids, providing energy for muscle contraction. Meanwhile, anabolic pathways like glycogen synthesis and gluconeogenesis are inhibited, prioritizing energy production over storage.

The breakdown of carbohydrates and fatty acids provides energy for muscle contraction during strenuous activity, allowing the body to meet the increased energy demands.

The body's intricate network of metabolic pathways ensures optimal use of available energy sources. When ATP is used for muscle contraction, AMP is released, signaling the need to produce more energy.

Metabolic pathways are interconnected, and their activities are fine-tuned to maintain energy balance. For example, during exercise, AMP levels rise, triggering the breakdown of carbohydrates and fats for energy.