Carbohydrate Structure

Carbohydrate Structure

• Monosaccharides: simplest form of carbohydrates, composed of 3-7 carbon atoms
  • Examples: glucose, fructose, galactose
  • Classified as aldoses (have an aldehyde group) or ketoses (have a ketone group)
• Disaccharides: formed by condensation reaction between two monosaccharides
  • Examples: sucrose (glucose + fructose), lactose (glucose + galactose)
• Polysaccharides: formed by condensation reaction between multiple monosaccharides
  • Examples: starch (glucose polymers), cellulose (glucose polymers), glycogen (glucose polymers)

Carbohydrate Metabolism

• Glycolysis: breakdown of glucose to pyruvate, occurring in cytosol
  • Generates ATP and NADH
  • Can occur anaerobically (without oxygen) or aerobically (with oxygen)
• Gluconeogenesis: synthesis of glucose from non-carbohydrate sources (e.g. amino acids, lactate)
  • Occurs in liver and kidneys
  • Reverses glycolysis pathway
• Glycogenolysis: breakdown of glycogen to glucose
  • Occurs in liver and muscles
  • Regulated by hormones (e.g. insulin, glucagon)
• Pentose Phosphate Pathway: generates NADPH and pentoses from glucose
  • Occurs in cytosol
  • Important for nucleic acid synthesis and antioxidant defenses

Regulation of Carbohydrate Metabolism

• Insulin: hormone that promotes glucose uptake and storage
  • Released by pancreas in response to high blood glucose
  • Stimulates glycogen synthesis and inhibits glycogenolysis
• Glucagon: hormone that promotes glucose release and breakdown
  • Released by pancreas in response to low blood glucose
  • Stimulates glycogenolysis and inhibits glycogen synthesis
• Other regulators: cortisol, thyroxine, and epinephrine also play roles in regulating carbohydrate metabolism

Carbohydrate Structure

• Monosaccharides are the simplest form of carbohydrates, composed of 3-7 carbon atoms.
• Examples of monosaccharides include glucose, fructose, and galactose.
• Monosaccharides are classified as aldoses (having an aldehyde group) or ketoses (having a ketone group).

Carbohydrate Classification

• Disaccharides are formed by a condensation reaction between two monosaccharides.
• Examples of disaccharides include sucrose (glucose + fructose) and lactose (glucose + galactose).
• Polysaccharides are formed by a condensation reaction between multiple monosaccharides.
• Examples of polysaccharides include starch (glucose polymers), cellulose (glucose polymers), and glycogen (glucose polymers).

Carbohydrate Metabolism

• Glycolysis is the breakdown of glucose to pyruvate, occurring in the cytosol.
• Glycolysis generates ATP and NADH.
• Glycolysis can occur anaerobically (without oxygen) or aerobically (with oxygen).
• Gluconeogenesis is the synthesis of glucose from non-carbohydrate sources (e.g. amino acids, lactate).
• Gluconeogenesis occurs in the liver and kidneys.
• Gluconeogenesis reverses the glycolysis pathway.
• Glycogenolysis is the breakdown of glycogen to glucose.
• Glycogenolysis occurs in the liver and muscles.
• Glycogenolysis is regulated by hormones (e.g. insulin, glucagon).
• The Pentose Phosphate Pathway generates NADPH and pentoses from glucose.
• The Pentose Phosphate Pathway occurs in the cytosol.
• The Pentose Phosphate Pathway is important for nucleic acid synthesis and antioxidant defenses.

Regulation of Carbohydrate Metabolism

• Insulin is a hormone that promotes glucose uptake and storage.
• Insulin is released by the pancreas in response to high blood glucose.
• Insulin stimulates glycogen synthesis and inhibits glycogenolysis.
• Glucagon is a hormone that promotes glucose release and breakdown.
• Glucagon is released by the pancreas in response to low blood glucose.
• Glucagon stimulates glycogenolysis and inhibits glycogen synthesis.
• Other regulators such as cortisol, thyroxine, and epinephrine also play roles in regulating carbohydrate metabolism.