3.3.3 Digestion and Absorption — Vocabulary Flashcards

Vocabulary flashcards covering key terms, enzymes, structures, and transport mechanisms involved in digestion and absorption as described in the notes.

Digestion

The process by which large molecules from food are broken down into smaller molecules that can be absorbed across cell membranes.

Hydrolysis

Chemical breakdown of polymers into monomers by the addition of water.

Amylase

Enzyme that hydrolyses starch into maltose; produced by salivary glands and pancreas.

Maltose

A disaccharide produced from starch; hydrolysed by maltase to glucose.

Maltase

Membrane-bound disaccharidase on the ileum epithelium that hydrolyses maltose to α-glucose.

Sucrase

Membrane-bound disaccharidase that hydrolyses sucrose into glucose and fructose.

Lactase

Membrane-bound disaccharidase that hydrolyses lactose into glucose and galactose.

Pepsin

Endopeptidase in the stomach that begins protein digestion by cleaving internal peptide bonds.

Endopeptidases

Enzymes that hydrolyse peptide bonds within the central region of proteins.

Exopeptidases

Enzymes that cleave terminal or penultimate peptide bonds to release amino acids or dipeptides.

Dipeptidases

Membrane-bound enzymes in the ileum that hydrolyse dipeptides into amino acids.

Lipase

Enzyme that hydrolyses triglycerides into fatty acids and monoglycerides (pancreatic lipase acts in the duodenum).

Bile salts

Bile components produced by the liver that emulsify fats to increase surface area.

Emulsification

Process by which bile salts break fats into smaller droplets, increasing the surface area for digestion.

Micelles

Tiny complexes formed by fatty acids, monoglycerides and bile salts that aid transport to the intestinal membrane.

Monoglycerides

Glycerol molecules with one fatty acid; products of lipid digestion that form micelles and are absorbed.

Fatty acids

Hydrolysis products of triglycerides that are absorbed by intestinal cells.

Chylomicrons

Lipid-protein particles formed in the ER and Golgi that transport triglycerides through the lymph (lacteals) and into the blood.

Lacteals

Lymphatic capillaries in the villi that take up chylomicrons for transport via the lymphatic system.

Villi

Finger-like projections in the small intestine that increase the surface area for absorption.

Microvilli

Brush-border projections on the surface of epithelial cells that further increase absorption surface area.

Ileum

Part of the small intestine where absorption occurs; epithelium is one cell thick.

Co-transport

Active transport mechanism where amino acids and monosaccharides are absorbed with sodium ions.

Facilitated diffusion

Passive transport of monosaccharides into cells via transporter proteins (e.g., fructose).

Osmosis

Movement of water across a selectively permeable membrane down a water potential gradient.

Diffusion gradient

A gradient maintained by intestinal movement that facilitates diffusion of nutrients.

Pancreas

Gland that secretes pancreatic juice containing proteases, lipases, and amylase into the duodenum.

Liver

Organ that produces bile; processes absorbed nutrients and detoxifies blood; stores glucose as glycogen (insulin).

Gallbladder

Stores and concentrates bile; releases bile into the small intestine when needed.

Duodenum

First section of the small intestine where chyme mixes with pancreatic juice and bile.

Peristalsis

Wavelike muscular contractions that move food along the digestive tract.

Stomach

Muscular sac that stores and digests food; contains proteases (e.g., pepsin) and begins protein digestion.

Absorption into blood

Process by which digested products (amino acids, glucose, galactose) enter the capillaries of the intestinal villi and are carried in the bloodstream.

Absorption into lymph

Process by which lipids (as chylomicrons) enter the lymphatic system via lacteals before entering the blood.