Which water-soluble vitamin must first be bound to the intrinsic factor secreted by the gastric mucosa before it can be absorbed by the intestinal epithelium?
What feature of phospholipids allows them to interact with aqueous cytosol and extracellular fluid, while still presenting a barrier to hydrophilic substances?
Which events occur during the recycling of aged or damaged erythrocytes? (Order is not important.)a: The heme group is converted into biliverdin.b: Bilirubin is placed in long-term storage in the liver.c: The iron ions in hemoglobin are removed.d: The iron ions are stored in the liver.e: The iron ions are stored in the red bone marrow.f: Membrane proteins and globin proteins are broken down and reused.g: The erythrocyte contents, excluding the globins, are excreted unchanged via the digestive tract.
Some studies theorize that yawning is a reflex triggered by increased blood pH as carbonic acid is produced to expel CO2 by exhaling. Which structures would be stimulated to induce yawning if this theory is true?