Digestion of Fats, Vitamins and Minerals Flashcards
What form is all fat ingested as?
Triacylglycerol (glycerol and 3 stearic acid tails)
What enzyme aids in digestion of fat?
Pancreatic lipase
What is the effect of lipase?
Triacylglycerol –> monoglyceride + 2 fatty acids
What is emulsification?
Division of large lipid droplets into smaller droplets –> increased surface area and accessibility for lipase action
Why is emulsification required?
As triacylglycerols are large lipid droplet which are insoluble in water and pancreatic lipase is a water soluble enzyme so digestion can only occur at a very slow rate as symes can only work of the surface of the droplet.
Emulsification increases surface area and accessibility for lipase action which allows for faster digestion
What are the requirements for emulsification?
Mechanical disruption (smooth muscle contraction grinds and mixes) Emulsifying agent - prevents small droplets reforming large ones
Name emulsifying agents
Bile salts + phospholipids Amphiphatic molecules (polar and non-polar portions)
Where are bile salts produced?
Liver
How do emulsifying agents work?
Non-polar portions associate with non-polar interior of lipid droplet, leaving polar portions exposed at water surface
Non-polar portions of smaller lipid droplets repel other droplets that are also coated with amphiphatic molecules, preventing them from reforming into large droplets
What are micelles?
Packaged up bile salt, monoglyceride, fatty acids, and phopholipids - to speed up absorption
Hydrophobic interior and hydrophilic exterior
How does micelle breakdown occur?
- Micelle is only stable at a high pH, so when it moves towards the lumen epithelium, the acid microclimate (low pH) causes the FFA to become protonates (uncharges) and this breaks down the micelle
- Release of small amount of free fatty acids and monoglycerides into solution –> diffusion across plasma membrane of absorbing cells
What happens to FFA and monoglycerides after absorption?
- They enter the smooth endoplasmic reticulum and are reformed into triacylglycerols
- An amphiphatic protein in cells coats the tria. droplets –> emulsification
- The vesicles are processed through the Golgi apparatus and are exocytosed into extracellular fluid as chylomicrons
- Chylomicrons are too large to travel between cells of the endothelium of capillaries, so they pass from lacteals of the lymphatic systems
Name 4 Fat-Soluble Vitamins
A, D, E, K
Name 3 water-soluble vitmains
B, C and folic acid
How are fat-soluble vitamins absorbed?
Same pathway as fat
