Nutrient digestion and absorption 2 Flashcards
What form is almost all ingested fat in?
Triacyglycerol
What is fat digestion in the small intestine carried out by?
Pancreatic lipases
What is triacyglycerol broken down into?
Monoglyceride + 2 fatty acid
What is emulsification?
Dividing large lipid droplets into smaller droplets
This increases surface area and accessibility to lipase action
What does emulsification require?
Mechanical distruption of large lipid droplets into small droplets
Emulsifying agent
Smooth muscle contraction grinds and mixes lumenal contents
Bile salts + phospholipids
Amphipathic molecules
What does an emulsifying agent do?
It prevents small droplets reforming into large droplets
What does polar portions repelling other small lipid droplets do?
Prevents reforming into large droplets
How is absorption of lipase digestion products enhanced?
By formation of micelles
What is a micelle composed of?
Micelle = bile salt + monoglycerides + fatty acids + phospholipids
What parts of the micelle are polar and non-polar?
Polar portions of molecules at micelle surface
Non-polar portions of molecules form micelle core
What does micelle breakdown cause?
Release of small amounts of free fatty acids and monoglycerides into solution
- causing diffusion across plasma membrane of absorbing cells
Are micelles themselves absorbed?
NO
Where do fatty acids and monoglycerides go after entering epithelial cells?
They enter smooth endoplasmic reticulum (sER) where they are reformed into triacylglycerols
What do chylomicrons pass into between endothelial cells?
They pass into lacteals between endothelial cells
- They cannot pass through capillary basement membrane
What is used to break down fat droplets?
Bile salts
Phospholipids
Pancreatic lipases
