Carbohydrate Metabolism in Humans

An overview of the biochemical processes involved in the breakdown and utilization of carbohydrates within the human body.

Initial Breakdown in the Oral Cavity

The role of salivary amylase in the hydrolysis of starch into smaller oligosaccharides. Factors affecting its efficacy, such as pH levels.

Digestion in the Small Intestine

Action of pancreatic amylase to further hydrolyze complex carbohydrates. Brush border enzymes (e.g., maltase, sucrase, lactase) and their specific roles in breaking down disaccharides into monosaccharides. Conditions affecting enzymatic activity.

Absorption of Monosaccharides

Mechanisms of monosaccharide absorption across the intestinal epithelium. Active transport of glucose and galactose via SGLT1. Facilitated diffusion of fructose via GLUT5. Transport of all monosaccharides to the liver via GLUT2.

Regulation of Blood Glucose Levels

The role of insulin in promoting glucose uptake by cells and glycogen synthesis in the liver and muscles. Glucagon's role in stimulating glycogenolysis and gluconeogenesis in the liver. The effect of other hormones, such as cortisol and epinephrine, on carbohydrate metabolism.

Metabolic Pathways of Glucose

• Glycolysis: The breakdown of glucose into pyruvate.
• Citric Acid Cycle (Krebs Cycle): The oxidation of pyruvate to produce energy.
• Electron Transport Chain: Generation of ATP from NADH and FADH2.
• Glycogenesis: Synthesis of glycogen for glucose storage.
• Glycogenolysis: Breakdown of glycogen to release glucose.
• Gluconeogenesis: Synthesis of glucose from non-carbohydrate precursors.

Factors Affecting Carbohydrate Metabolism

Impact of diet composition (types and amounts of carbohydrates). Influence of physical activity on glucose utilization. Effects of various medical conditions (e.g., diabetes, enzyme deficiencies) on carbohydrate metabolism. Influence of gut microbiota composition.