Biochemistry Chapter: Glycogen Metabolism

Cytokines are small proteins produced by various cell types, primarily immune cells. They act as signaling molecules, regulating the development, function, and interactions of immune cells.

Cytokines play a crucial role in the development and balance of the immune system. They ensure proper functioning of immune cells like T cells, B cells, and macrophages.

Cytokines control the production of various blood cells, including red blood cells, white blood cells, and platelets, by influencing the hematopoietic stem cells.

Cytokines are involved in the body's non-specific defense against pathogens. They influence inflammation, blood clotting, and blood pressure regulation.

Cytokines regulate the growth, development, and survival of cells. They can promote cell division, differentiation, or even induce cell death.

Cytokines play a crucial role in programmed cell death, a process where cells self-destruct in a controlled manner.

Interleukins (IL) are a family of cytokines primarily produced by leukocytes (white blood cells). They play diverse roles in immune responses.

Interferons (IFN) are a group of cytokines primarily produced by virus-infected cells. They have antiviral, antitumor, and immunomodulatory functions.

Process of converting glucose into glycogen for storage.

The storage form of carbohydrates in animals, composed of branched chains of glucose molecules.

Glycogen is synthesized in the liver and muscles.

Glucose is linked together by α 1-4 glycosidic bonds, with branches formed by α 1-6 glycosidic bonds.

Muscle glycogen provides energy to the muscle itself, while liver glycogen maintains blood glucose levels between meals.

Insulin activates glycogen synthase, causing it to convert glucose into glycogen (glycogenesis).

Glucagon and epinephrine inhibit glycogen synthesis by activating adenyl cyclase, which converts ATP into cAMP (cyclic AMP). cAMP activates protein kinase A, leading to the inactivation of glycogen synthase.

Glycogenolysis is the breakdown of glycogen into glucose subunits.

Glycogen phosphorylase is the primary enzyme involved in glycogenolysis. It hydrolyzes 1,4-glycosidic bonds in glycogen, releasing glucose-1-phosphate.

After glycogenolysis, glucose-1-phosphate is converted to glucose-6-phosphate by phosphoglucomutase.

In the liver, glucose-6-phosphate is converted to free glucose by glucose-6-phosphatase. This free glucose is then released into the bloodstream.

In muscle cells, glucose-6-phosphatase is absent. So, glucose-6-phosphate is used for energy production.

Glycogenolysis occurs primarily in the liver and muscle. The liver releases glucose into the bloodstream to raise blood glucose levels, while muscle cells use glucose-6-phosphate for energy.

The reaction catalyzed by pyruvate kinase is irreversible, meaning it cannot proceed in the reverse direction.

The product of the pyruvate kinase reaction, enol pyruvate, spontaneously isomerizes to pyruvate without requiring an enzyme.

Under anaerobic conditions, the lack of oxygen prevents the re-oxidation of NADH through the respiratory chain.

In anaerobic conditions, pyruvate is reduced to lactate by NADH, a process catalyzed by lactate dehydrogenase.

Lactate production regenerates NAD, allowing glycolysis to continue in the absence of oxygen.

Under aerobic conditions, pyruvate enters the mitochondria and is converted to acetyl CoA, initiating the Krebs Cycle.

Two molecules of NADH produced during glycolysis are transported to the mitochondria by the malate shuttle.

In red blood cells (RBCs), glycolysis always ends with lactate production, even under aerobic conditions, due to the absence of mitochondria.

The process of breaking down glycogen into glucose.

The formation of glucose from non-carbohydrate sources like fats and proteins.

The breakdown of glucose into pyruvic acid or lactic acid.

When blood glucose levels exceed the normal renal threshold, usually around 180 mg%.

The pentose phosphate pathway (PPP) generates NADPH, a reducing agent that protects red blood cells from oxidative damage.

A genetic deficiency in glucose-6-phosphate dehydrogenase (G6PD) can lead to hemolytic anemia or Favism, a condition characterized by red blood cell destruction.

Glutathione reductase uses NADPH to reduce oxidized glutathione, which in turn helps remove harmful hydrogen peroxide (H2O2) from red blood cells.

Glucuronic acid is a derivative of glucose involved in forming proteoglycans and heparin, and is essential for the excretion of various substances from the body.

The lack of the enzyme gulonolactone oxidase in humans makes us reliant on dietary vitamin C, unlike most other mammals.

Lactose synthase, an enzyme found in mammary glands, catalyzes the synthesis of lactose by combining UDP galactose with glucose.

Amino sugars, essential components of various biomolecules, are derived from glucose.

The major amino sugar is N-acetylneuraminic acid (NeuAc), also known as sialic acid, found in human tissues.