Digestion: Process where large insoluble molecules are hydrolyzed into smaller soluble molecules for absorption into the bloodstream.
Focus on precise use of keywords and terms for examination.
Digestion Process
Carbohydrates
Involves enzymes like amylases (produced in pancreas and salivary glands) and membrane-bound disaccharidases.
Amylase: Starts digestion in the mouth, hydrolyzing polysaccharides (e.g., starch) into disaccharides like maltose by breaking glycosidic bonds.
Membrane-bound disaccharidases: Located in the duodenum and ileum, converting disaccharides to monosaccharides (e.g., sucrose to fructose and glucose, lactose to galactose and glucose).
Proteins
Enzymes: Endopeptidases, exopeptidases, and dipeptidases.
Endopeptidases: Hydrolyze peptide bonds within polymer chain.
Exopeptidases: Act at the chain ends.
Dipeptidases: Break bonds between two amino acids.
Begins in the stomach and continues into the duodenum and ileum.
Lipids
Involves both chemical digestion by enzymes and physical breakdown with bile salts.
Lipase: Produced in the pancreas, hydrolyzes ester bonds in triglycerides to produce fatty acids and glycerol or monoglycerides.
Bile Salts: Produced in the liver, stored in the gallbladder, emulsify lipids to increase surface area for lipase action.
Micelles: Formed by fatty acids and monoglycerides with bile salts, aiding in delivery to epithelial cells.
Absorption Process
General Mechanism
Occurs in cells lining the ileum (small intestine).
Villi and Microvilli: Increase surface area for absorption; villi contain capillary networks to maintain concentration gradients.
Specific Absorption
Monosaccharides and Amino Acids: Absorbed via co-transport (active transport) and facilitated diffusion.
Co-transport is essential when higher concentrations inside the cells prevent facilitated diffusion.
Lipids:
Micelles deliver fatty acids and monoglycerides to epithelial cells.
Lipids diffuse due to non-polar nature.
Reformation into triglycerides occurs in the Golgi apparatus, sometimes forming chylomicrons (triglycerides plus proteins).
Chylomicrons are released by exocytosis and absorbed into lymphatic vessels (lacteals) for transport.
Important Points
Emphasis on the importance of enzymes and bile in digestion.
Highlighting the role of surface area in enhancing enzyme action and absorption.
Understanding transport mechanisms (active and facilitated) for different nutrients.