Carb/Fat/Protein digestion and absorption Flashcards
How much of your nutrients are absorbed by the time a meal reaches the distal jejunum?
95%
What is the purpose of segmenting contractions?
Mixing facilitation
What three enzymes are responsible for disaccharide cleavage in the brush border?
Maltase
Sucrase
Lactase
What product inhibits lactase activity?
Glucose
What prevents protease degradation of brush border enzymes?
Heavy glycosylation
What are the causes of lactose intolerance?
Secondary after injury to absorptive cells due to Crohn’s, celiac, or alcohol
Normal decrease in lactase activity
What transporters are important in sequestering monosaccharides from bacteria?
SGLT1: Na-Glucose/Galactose cotransporter
GLUT5: Fructose transporter
What type of transporter is SGLT1?
Secondary active transporter
Symporter
What enzyme transports monosaccharides across basolateral membrane?
Glut2
What initiates amino acid degradation in the stomach?
Pepsin
If an enzyme is rich in this amino acid, it is resistant to digestion.
Proline
What is often transported along with amino acids on the luminal side transporters?
Sodium
What is transported with peptides with PEPT1? In what direction?
Protons
Opposite (antiporter)
What is the cotransported ion with peptides?
Protons
What is the process of protein absorption in infants like?
Endocytosis (passive immunity)
What is the role of intestinal M cells?
Take up antigens and presents them to lymphocytes
What cells secrete gastric lipase?
Chief cells
Why is gastric lipase important in neonates?
Developmental delay of pancreatic enzyme expression
What cells secrete pancreatic lipase and procolipase?
Acinar cells
What activates colipase?
Trypsin
What do bile acids do to lipase activity? What remedies that?
Bile acids inhibit lipase activity, collipase remedies it
What is the role of phospholipase A2?
Cleaves phospholipids from cell membranes into fatty acids and lysophospholipids
What enzyme hydrolyzes cholesterol esters?
Cholesterol esterase
What is orlistat?
Pancreatic lipase inhibitor
What is olestra?
Undigestable fat too big to be absorbed
What is the role of bile salts and phospholipids?
Break up fat globules into droplets
How do lipids enter enterocytes?
Nonionic diffusion
Collision with membrane
Carrier mediated transport
What coats triglycerides to form chylomicrons?
Apoproteins
Where does chylomicron synthesis occur in the enterocyte?
Smooth ER
What cells secrete intrinsic factor? What does it do?
Parietal cells
Binds B12 and protects it from degrading
What common drug interferes with absorption of B12?
Metformin
