Carbohydrates II: Glycogen Metabolism, the Pentose Phosphate Pathway, Glycoconjugates, and Extracellular Matrices

Flashcards about Carbohydrates II: Glycogen Metabolism, the Pentose Phosphate Pathway, Glycoconjugates, and Extracellular Matrices

What is Glycogen?

A stored form of glucose that is a highly branched polymer of α-1,4 and α-1,6 linked glucose monomers with a glycogenin protein core; synthesized and degraded in situ, regulated by epinephrine and norepinephrine.

What is Glycogenesis?

The synthesis of glycogen requiring glycogenin, glycogen synthase, and branching enzyme.

What is Glycogenolysis?

The breakdown of glycogen into glucose, requiring glycogen phosphorylase and glycogen debranching enzyme.

How is Glycogen metabolism regulated?

Glycogen phosphorylase and glycogen synthase are regulated mainly by PKA. ATP and glucose-6-phosphate act as allosteric regulators. Phosphorylation determines enzyme activity.

What is the role of Protein Phosphatase 1 (PP1)?

It is an enzyme anchored in the cytosol in a complex with other proteins that regulate glycogen metabolism. It acts as a scaffolder to GM, a phosphatase that targets glycogen molecules.

What is the effect of insulin signaling on glycogenesis and glycogenolysis?

Insulin stimulates glycogenesis and blocks glycogenolysis by stimulating PP1.

What is the Pentose Phosphate Pathway?

A pathway that produces monosaccharides, NADPH, and antioxidants, divided into oxidative and nonoxidative phases.

What are epimers?

Isomers that differ only in stereochemistry about a single chiral center, such as galactose (C-4 epimer) of glucose.

What are transketolases?

Enzymes that use thiamine pyrophosphate (TPP) and an aldose substrate to form a ketose.

What are transaldolases?

Enzymes that use an active lysine to form a Schiff base with an aldose substrate and a carbonyl carbon to form a ketose.

What is the role of glutathione in the pentose phosphate pathway?

It is a tripeptide antioxidant that neutralizes reactive oxygen species. Glutathione dehydrogenase uses NADPH to reduce the disulfide bond and produce 2 molecules of glutathione.

What is Carbohydrate Response Element-Binding Protein (ChREBP)?

A transcription factor that responds to high levels of carbohydrates, regulating genes involved in carbohydrate and lipid metabolism. It is activated by xyulose-5-phosphate and increases the expression of genes involved in energy storage.

What are glycoproteins?

Membrane-bound or extracellular proteins with carbohydrate modification (N-linked or O-linked) that regulate enzyme activity, protein stability, protein folding and trafficking.

What are glycolipids?

Membrane phospholipids with a carbohydrate moiety exposed to the external environment, containing a glycerol or sphingosine backbone. Examples include lipopolysaccharides, glycosylphosphatidylinositol (GPI), cerebrosides, and gangliosides.

What are proteoglycans?

Extensive mesh nets of polysaccharides joined to fibrous proteins, a major component of the extracellular matrix, containing a glycosaminoglycan and a protein core.

What are peptidoglycans?

Lengthy chains of polysaccharides cross-linked by peptides, found in bacterial cell walls, composed of a dimeric repeat of N-Acetylglucosamine (GlcNAc) and N-Acetylmuramic acid (MurNAc) in a β-1,4 linkage.

What is the extracellular matrix?

A tissue made of proteins, glycoproteins, and proteoglycans in a fibrous, gel-like mesh, involved in ligand binding, immune response, and regulation of growth and development.

What is Collagen?

A protein found in high amounts in the extracellular matrix with a Gly, Pro, and Lys triple helix.

What is Elastin?

A protein responsible for the core of elastic fibers found in skin and arteries composed of largely hydrophobic residues.

What is Fibronectin?

A protein found in the extracellular matrix, functioning in the clotting cascade and acting as an adapter between the cell and the matrix.

What are Laminins?

A family of proteins that function in the basal lamina, a layer of the basement membrane, a fibrous layer of connective tissue found under the epithelial layers.

What is the Interactome?

The description of how large matrix proteins interact with other macromolecules.

What is Cell Culture?

A process in which cells are grown on a plastic tissue culture dish for researchers to study cells under different conditions.

What is Tissue engineering?

The growth of cultured cells in a three-dimensional matrix, where the scaffold provides structure for the cells to grow.

What are Biofilms?

Associations of microbes living in a secreted matrix, often found at an air–liquid or solid–liquid interface.

What is Gluconeogenesis?

A pathway used to circumvent the two irreversible steps in glycolysis, involving pyruvate carboxylase and PEP carboxykinase.

What is Pyruvate Carboxylase?

A vitamin B7-containing enzyme that converts pyruvate to oxaloacetate in the mitochondria.

What is PEP Carboxykinase?

An enzyme that phosphorylates oxaloacetate and decarboxylates it to phosphoenolpyruvate (PEP).

What is Fructose-1,6-Bisphosphatase?

Conversion of fructose-1,6-bisphosphate to fructose-6-phosphate, bypassing phosphofructokinase-1, catalyzed by fructose-1,6-bisphosphatase.

What is Glucose-6-Phosphatase?

Conversion of glucose-6-phosphate to glucose, bypassing hexokinase, catalyzed by glucose-6-phosphatase in the liver ER.

What is the Cori Cycle?

A cycle involving the interconversion of lactate and glucose between the muscle and liver.

A cycle involving the interconversion of alanine and glucose between