Lipid-Digestion & Absorption Flashcards
1
Q
What increases surface area for absorption?
A
- Crypt
- Villi
- Microvilli
2
Q
Stem Cells of crypt
A
- produce new absorptive epithelial cells to replace lost cells
3
Q
Lacteal
A
transport fat to lymph
4
Q
What can lead to malabsorption of lipids?
A
- Bile deficiency
- Pancreatic Insufficiency
5
Q
Digestion and absorption of lipids
A
- Bile salts-emulsify fats
- Pancreatic lipase-digest
- Pancreatic co-lipase-facilitate digestion
- Absorption in small intestins
- Resynthesized as chylomicron
- DOES NOT ENTER PORTAL VEin
- enters lacteals–>lymphatics
6
Q
Triglycerides are digested by and into?
A
- Lipase/colipase
- Monoglycerides
- free fatty acids
7
Q
Key enzymes in lipid digestion
A
Lipase
Colipase
Prophospholipase-A2
Cholesterol Esterase
8
Q
Bile Salts
A
- amphipathic molecules
- Polar/hydrophilic-water
- Nonpolar/Hydrophobic-Lipids
- Coat lipids to emulsify
9
Q
Digestion & Absorption of Fats: Steps
A
- 1)Bile salts from liver coat fat droplets
- 2)Pancreatic Lipase and colipase breakdown fats into monoglycerides and Fattyacids stored in micelles
- 3a)Monoglycerides and FAs move out of micelle and enter cell by difusion
- MVM-FABP
- 3b) Cholesterol is transported into cells by a membrane transporter=NPC1L1 (inhibited by Ezetimibe)
- 4) absorbed fats combine with cholesterol and proteins in the intestines to form chylomicrons
- series of apolipoproteins
- 5) Chylomicrons released into lymphatic system by exocytosis
- EXCEPTION:
- Chylomicron-mediated fat transport is for MCFA
- water soluble
- pass through tight junction
- Chylomicron-mediated fat transport is for MCFA
10
Q
Re-esterification of digested lipids by enterocytes
A
*
11
Q
What is olestra: Olestra
A
- Fat substitute
- 6-8 fatty acids attached to sucrose
- resistant to lipase digestion
- too big to be reabsorbed
- Food additivei n 1998
- Original FDA warning label
- abdominal cramping
- loose stools
- inhibits the absorption of some vitamins and nutreints
- Vitamins A, D, E, and K have been added
- Unabsorbed in small intestine–passes to colon
- Colonic microflora metabolize
- osmotic particles, intestinal gas, potential for diarrhea (anal leakage)
- solution-diminish quantity ingested
- Still forms micelles in GI Lumen
- fat souble vitamins not absorbed
- solution-supplement with extra fat soluble vitamins
12
Q
Malabsorption of Fat causes
A
- Bile salt deficiency
- Fat soluble vitamin deficiency (A,D, E, K)
- Steatorrhea
- Obstruction of bile flow
- cystic and bile ducts
- Ileal resection
- gallstones (Cholelithiasis)
- Problems with:
- bile synethesis-hepatocytes
- Enterohepatic circulation
- Liver disease (Cirrhosis)
13
Q
Fat Soluble Vitamin Deficiency
A
Deficiencies
- Vitamin A
- night blindness
- Vitamin D
- decreased Ca2+ absorption
- osteoporosis
- bone pain
- fractures
- Vitamin K
- prolongs prothrombin time
- purpura (bruising)
- petechiae
- red spots on skin
- minute hemorrhage due to broken capillaries in the skin
- Vitamin E
- uncertain but may:
- testicular atrophy
- neurologic defects in children
- antioxidant
- uncertain but may:
14
Q
Phases of Food Processing by GI tract
A
- Cephalic Phase
- Gastric Phase
- Intestinal Phase (early and late)
15
Q
Cephalic Phase
A
- Chemical and mechanical digestion begins in the mouth
- mastication
- Salivary Secretion
- autonomic control
- softens and lubricates food
- Chemical Digestion
- salivary amylase
- some lipase
- Saliva contains protective agents
- Deglutition(Swallowing( moves food from the mouth to the stomach
- initiated by stimuli
- activates PNS
- small rise in plasma gastrin
- neurohumoral factors increase:
- salivary
- gastric
- pancreatic secretions
- Gallbladder contracts and sphincter of oddi relaxes
- prepares stomach for food and digestion
