Nutrient digestion and absorption 2 Flashcards
what are most fats made of?
A glycerol + 3 steric acids
what are fats broken down by? and what into?
pancreatic lipase
monoglyceride and 2 FAs
Problems with triacylglycerol being broken down by lipase
- Triacylglycerol is insoluble in water
- Lipase is water soluble enzyme
- Lipase can only break down the triacylglycerol at the surface and slow
What is emulsification?
when triacylglycerol is broken down into smaller droplets
How does emulsification occur?
- Mechanical disruption in the stomach
- Emulsifying agents: bile salts and phospholipids
What is the purpose of emulsification?
- increases SA SO
- increases lipase action
characteristics of emulsifying agents?
Amphipathic molecule:
- polar end: interacts with h20
- non-polar end: interacts with lipids.
Polar ends on molecules repel each other- prevents reformation of larger droplets
How to further increase digestion of fats after emulsification?
formation of micelles
What are micelles made of?
-bile salts/phopholipids
AND
-monglycerides/FA
Do micelles enter the cell
No they are just the transporter
- They get broken down by lipase to release FA and monoglyerides into solution
- Dynamic equilibrium established: the micelles ensure the FA and monoglycerides which are not taken up stay in solution so they can diffuse into the cell
What happens to the FA and monoglycerides once the enter the cell
- They are reformed into triacylglycerol by the SER
- Then they are covered in amphipathic proteins- allows emulsification
- they are then taken to the Golgi apparatus to converted into CHYLOMICRONS
- they then pass into the lymphatic system via lacteals
Why are the chylomicrons not passed into the blood?
They are too big to pass through tight junctions
How do vitamins get absorbed?
Fat-soluble ones: take the same route of Fats from the SER
water-soluble ones: passively diffusion or are carried by mediator molecules
B12: it is a charged molecule so has to bond to in stomach to form a complex
Absorption of iron
Across brush border by DMT1 into duodenum
Iron ions are incorporated ferritin
unbound iron is passed into the blood where it binds to transferrin
what is ferritin and what do its levels depend on?
it is an intracellular store of iron
It’s expression depends iron levels in the bloo
when iron levels are low-ANEMIA- less ferritin
when iron levels are high- HYPEREMIA- more ferritin
