Carbohydrate

• Incomplete digestion of carbohydrate can lead to fermentation in the large intestine, producing methane and carbon dioxide.
• The salivary glands produce amylase in the mouth, which breaks glycosidic bonds in starch to form maltose.
• The pancreas releases pancreatic enzymes into the small intestine to break glycosidic bonds and hydrolyse starch into maltose.
• The small intestine (the ileum) has membrane-bound disaccharidases in the membranes of epithelial cells, which break glycosidic bonds to hydrolyse disaccharides into monosaccharides.

  For instance, sucrase catalyses the breakdown of sucrose into glucose and fructose.
• 𝘿𝙄𝙎𝘼𝘾𝘾𝙃𝘼𝙍𝙄𝘿𝙀𝙎:

  • sucrose:

  glucose + fructose

  hydrolysed by sucrase

  • lactose:

  glucose + galactose

  hydrolysed by lactase

  • maltose:

  glucose + glucose

  hydrolysed by maltase
• Polysaccharides and disaccharides are digested into monosaccharides via the hydrolysis of glycosidic bonds.
• When disaccharides are digested, the monosaccharide products are small enough to be transported across the epithelium cell membrane (through specific transporter proteins) and into the capillaries.
• Glucose and galactose are actively transported using sodium ions through co-transporter proteins.
• Fructose is absorbed by facilitated diffusion through a different transporter protein.
• Digestion of carbohydrates:

  • Takes place in the mouth and small intestine
  • Starch digestion starts in the mouth under the action of ptyalin or salivary amylase
  • Continues in the jejunum and ileum of the small intestine with the help of pancreatic juice and intestinal juice
• Carbohydrate Absorption:

  • Monosaccharides glucose and galactose are absorbed through co-transport (secondary active transport) and facilitated diffusion
  • Monosaccharide fructose is absorbed and transported through facilitated diffusion
• Describe the complete digestion of starch by a mammal.

  1. Hydrolysis;
  2. of glycosidic bonds;
  3. Starch to maltose by amylase;
  4. Maltose to glucose by maltase;