Nutrient digestion and absorption 2 Flashcards
in what form is almost all fat ingested
triacylglycerol
where does all fat digestion take place
small intestine
what enzyme is responsible for digestion of fats in the small intestine
pancreatic lipase
what do triacylglycerols present as
large lipid droplets which are insoluble
what is a water soluble enzyme
lipase
where is the only place digestion can take place for a droplet
on the surface
slow process
when triacylglycerol is digested by lipase what is formed
monoglyceride and 2 fatty acids
what do bile salts act as
emulsifiers or surfactants
emulsification
ividing large lipid droplets into smaller droplets (~1 mm diameter) ⇒ increased surface area and accessibility to lipase action.
what does emulsification require
Mechanical disruption of large lipid droplets into small droplets.
Emulsifying agent - prevents small droplets reforming into large droplets.
mechanical disruptor
Smooth muscle contraction grinds and mixes lumen contents.
Emulsifying agent
Amphiphatic molecules (ie polar (charged) and non-polar portions)
where is bile released
duodenum
what prevents fats reforming into large droplets
Polar portions repel other small lipid droplets (also coated with bile salts/phospholipids) ⇒ prevent reforming into large droplets
what can enhance absorption of lipid digestion
formation of micelles
what are micelles
similar to emulsion droplets but much smaller
Micelle = bile salt + monoglycerides + fatty acids + phospholipids
what makes up a micelle surface
polar portions (bile salts)
what makes up a micelle core
non polar portions
Micelle breakdown
release of small amounts of free fatty acids (FFA) and monoglycerides into solution
then diffuse acriss plasma membrane of absorbing cells
Dynamic equilibrium
between fatty acids and monoglycerides in solution and in micelles - retains most of fat digestion products in solution while constantly replenishing supply of free molecules for absorption.
what does the ER contain
triacylglycerol synthetic enzymes
what is released from basolateral membrane of epithelial cells
chylomicron
chylomicron
Chylomicrons are composed of a main central lipid core that consists primarily of triglycerides, however like other lipoproteins, they carry esterified cholesterol and phospholipids
doesnt absorb through blood, to move in blood they must go in certain forms eg low density lipoprotein or HDL
what happens after entering epithelial cells
fatty acids and monoglycerides enter smooth endoplasmic reticulum (sER) where they are reformed into triacylglycerols (by enzymes located within the sER)
