Carbohydrate Metabolism Overview

Carbohydrate Metabolism Overview

• Carbohydrates are broken down into monosaccharides for energy or storage
• Main monosaccharides: glucose, fructose, galactose
• Glucose is the primary energy source for most cells
• Glycolysis, pentose phosphate pathway, and glycogenolysis are crucial pathways

Glycolysis

• Series of 10 enzyme-catalyzed reactions
• Occurs in the cytoplasm
• Converts glucose into two pyruvate molecules
• Produces a small amount of ATP and NADH
• Two phases: energy investment and energy payoff

Pentose Phosphate Pathway

• Alternative pathway for glucose metabolism
• Occurs in the cytoplasm
• Generates NADPH for reductive biosynthesis and antioxidant defense
• Produces ribose-5-phosphate for nucleotide synthesis

Gluconeogenesis

• Synthesis of glucose from non-carbohydrate precursors
• Occurs mainly in the liver and kidneys
• Crucial for maintaining blood glucose levels
• Uses a different set of enzymes compared to glycolysis, with bypass reactions

Glycogen Metabolism

• Glycogen: storage form of glucose in animals
• Glycogenesis: synthesis of glycogen from glucose
• Glycogenolysis: breakdown of glycogen into glucose
• Regulated by hormones like insulin and glucagon
• Primarily occurs in the liver and muscles
• Different functions in the liver (blood glucose homeostasis) and muscle (energy source during exercise)

Cori Cycle

• Interconnected pathways between muscle and liver
• Muscle glycogen is broken down during exercise, yielding lactate
• Lactate is transported to the liver, where it is converted to glucose
• Glucose is then transported back to the muscle for use

Fructose and Galactose Metabolism

• Fructose and galactose are metabolized by specific pathways
• Fructose metabolism differs slightly, entering glycolysis at different points.
• Galactose metabolism also has distinct steps in the pathway
• Defects in these pathways lead to specific metabolic disorders

Regulation of Carbohydrate Metabolism

• Hormonal regulation plays a critical role
• Insulin promotes glucose uptake and storage
• Glucagon promotes glucose release from storage
• Other hormones, like epinephrine, also involved in response to stress and energy demands
• Enzyme activity is also regulated through feedback mechanisms, allosteric control, and covalent modification.

Disorders of Carbohydrate Metabolism

• Many genetic and acquired disorders can affect carbohydrate metabolism
• Diabetes mellitus is a common disorder
• Characterized by hyperglycemia (high blood glucose) due to insufficient insulin production or action.
• Many other conditions affect glycogen storage, breakdown, synthesis and can lead to specific symptoms, depending on the affected pathways.

This quiz covers the essential pathways of carbohydrate metabolism, including glycolysis, the pentose phosphate pathway, and gluconeogenesis. You'll learn about the breakdown of carbohydrates into monosaccharides, the production of energy, and the synthesis of glucose from non-carbohydrate sources. Perfect for students studying biochemistry or related fields.