Lecture 5 Nutrient Digestion and Absorption Flashcards
What is the majority of digested fat in the form of
Triacylglycerol
Where does all fat digestion occurs
In the small intestine by pancreatic lipase
What type of enzyme is lipase
Water soluble
Why is digestion a very slow process
It can only take place at surface level of droplet
Define Emulsification
dividing large lipid droplets into smaller droplets (~1mm diameter) which increases surface area and accessibility to lipase action and prevent them forming large droplets again
What are the requirements of emulsification
- Mechanical Disruption of large lipid droplets to small
- Smooth muscle contractions
- Emulsifying agents
How does emulsifying agents such as bile prevent large droplets reforming
Non-polar portions of amphiphatic molecules (bile salts and phospholipids) associated with non-polar interior of lipid droplet leaving polar portions exposed at water surface
What enhances absorption of fat
Formation of Micelles
What are micelles
Bile salt + monoglycerides + 2 fatty acids + phospholipids (smaller than emulsion droplets)
What forms the polar portion and non-polar portion of micelle
Polar portion of molecules at micelle surface; non-polar portion form micelle core
What is critical for the transport of fat soluble minerals
Bile acids
What does the breakdown of micelles lead to
Free fatty acids (FFA) and monoglycerides that diffuse across the plasma membrane
What happens when FFA and monoglycerides when they enter epithelial cells
They enter smooth Endoplasmic Reticulum where they are reformed as tricylglycerols by enzymes located there and processed through Golgi apparatus and exocytosed to ECF
What are chylomicrons
Extracellular fat droplets
Where do chylomicrons pass through
Lacteals (lymphatic vessels) as they cannot pass through capillary basement membrane
