Lecture 51- Digestion And Absorption Of Lipids; Absorption Of Vitamins And Minerals Flashcards
What are the three main lipids?
Triglycerides (glycerol + 3 fatty acids)
Cholesterol
Phospholipids
How are lipids provided in diet for domestic animals?
Oils of vegetable or marine origin
Animal fats (tallow, lard, grease)
Dietary lipids must be solubilized in the ________ for digestion and absorption.
Small intestine
What is the function the stomach churning?
Churning breaks lipids into small droplets to increase surface area for enzymes
Mixes lipids, initiates enzymatic digestion
What does gastric lipase do?
Hydrolysis 10% of ingested TAG into glycerol + FFAs
What does the stomach slowly empty into the SI?
Chyme
How does the small intestine digest lipids?
- BILE SALTS EMULSIFY LIPIDS
- PANCREATIC ENZYMES DIGEST DIFFERENT LIPIDS
What does lipase + collapse allow?
Collapse binds to lipase and allows it to digest at lipid-water interface
What does cholesterol ester hydrolase do?
Hydrolyzes cholesterol ester -> free cholesterol + FA + releases glycerol from triglycerides
What is phospholipase A2 activated by?
Trypsin
What does phospholipase A2 hydrolyze?
It hydrolzyes phospholipids into lysolecithin + FA
What do bile salts solubilize products with SI lumen as _______.
Micelles
What does the core of the micelle contain? What is it surrounded by?
Contains products
Surrounded by bile salts
What does NOT diffuse into the enterocyte?
Bile salt
Re-estrified lipids + apoproteins = ________
Chylomicron
What is a chylomicron made up of?
Have cholesterol + TG in core, phospholipids + apoproteins around outside
Need to solubilize for absorption
What are lymphatic capillaries?
Chylomicrons can move between endothelial cells of lymphatic capillaries enter the blood at the thoracic duct
What are the five steps for the absorption of lipids?
- Bile salts solubilize products within SI lumen as micelles (except glycerol)
- Micelles diffuse to brush-border membrane of enterocyte, products released and diffuse into cell
- Products are re-sterilized inside enterocyte to form original compounds
- Re-sterilized lipids are packaged with apoproteins to form chylmoicrons
- Chylmicrons packaged in secretory vesicles and exocytosed across basolateral membrane into lymphatic capillaries
What is NOT solubilized within SI lumen as micelle?
Glycerol
What are 6 abnormalities of lipid digestion and absorption?
- Pancreatic insufficiency
- Acidity of duodenal contents
- Deficiency of bile salt
- Bacterial overgrowth
- Decreased intestinal cells for absorption
- Failure to synthesize apoproteins
What is the pH optimum for lipase?
6
When does a tumor arise?
When there is an over production of gastrin
What is ileal resection ?
No bile salt recycling
What does a lack of Apo B causes ?
Abetalipoproteinemia
Chhylomicrons dont form and cant transport entothyroctes -> lymph
For vitamin absorption what is required?
Co-enzymes or co-factors
FOR metabolic reactions
Within the SI lumen,what is incorporated into micelles for absorption?
Fat-soluble vitamins
What is incorporated into chylomicrons for transport?
Fat-soluble vitamins
How are most water-soluble vitamins absorbed?
What is the exception?
Na+/dependent co-transport in SI
Vitamin B12 (cobalamin), which required inter since factor for absorption
What are the steps for B12 absorption?
- B12 released from food by pepsin
- B12 binds to R proteins from salivary secretions
- Proteases in SI degrade
- B12/IF complex resists proteases, travels to ileum for absorption
What vitamin do you need to absorb calcium in SI?
Vitamin D
(TRUE/FALSE) Calcium is absorbed by both passive and active transport mechanisms
TRUE
How is vitamin D activated
Dietary vitamin D (cholecalciferol) -> 25-hydroxycholecalciferol in liver -> 1,25-dihydrocygcholecalciferol in kidney
What does active vitamin D promote synthesis of?
Calbindin D-28 K
What does a lack of active vitamin D or calcium result in?
Rickets and osteomalacia
What does heme iron mean?
Iron bound to hemoglobin or myoglobin
What is the iron transporter in the luminal membrane?
DMT-1
What is the heme iron digested into free iron by?
Lysosomal enzymes inside enterocytes
What does iron circulate bound to? What is it stored as?
Iron circulates bound to transferrin
Stored as ferritin
What does free iron bind to inside the enterocyte?
Apoferritin
What does free iron bind to in the plasma?
Transferrin
