Nutrients and Digestion Absorption: Fats, Vitamins and Minerals ** Flashcards
What form is all fat ingested in and what components make this up
Triaglycerol
Made up of one Glycerol and three stearic acids
What breaks down fat
Pancreatic lipase
Why does fat digestion take place at the surface of the lipid droplet
Triaglycerol is a Lipid droplet and is insoluble in water
and Lipase is a water soluble enzyme so breaks down from the outside in - very slow
What is the products of lipase break down of triaglycerol
Monoglyceride and 2 fatty acids
What is the purpose of emulsification
Increasing the surface area so is more accessible to lipase to quicken the process of digestion
Define emulsification
Dividing large lipid droplets into smaller lipid droplets
What is the requirements of Emulsification
Mechanical disruption
Emulsifying agent
How does mechanical disruption occur in the small intestine
smooth muscle from the muscular externia contracts grinding and mixing lumenal contents
What is the purpose of emulsifying agents
Prevent smaller droplets reforming into larger droplets again
What are the emulsifying agents used in fat digestion and where are they secreted from
Bile salts and phospholipids secreted in bile
What is the purpose of emulsifying agents being amphiphatic
The non polar molecule is lipid soluble to acts on lipid droplet while the polar molecule is non lipid soluble so sits on the water surface/outside the lipid and because its charged repels other lipid molecules re-combining with lipid droplet
Why is absorption still considered slow after emulsification and what enhances the absorption further from the small intestine
Lipids are still water insoluble and surrounded by an Aq environment
Micelles enhance further absorption
What is the purpose of Micelles
Transport the fat droplet to the intestinal cell for absorbtion
What is a micelles composed of
bile salt + monoglyceride + fatty acids + phospholipid
Whats the position of the the polar and non polar lipid molecule in reference to the micelle
Polar portions of molecules at micelle surface; non-polar portions form micelle core
What is the purpose of the polar portion of the lipid molecule being at the micelle surface
Prevent combining of micelles
What is the main difference between an emulsification droplet and micelle droplet
Micelles similar to emulsion droplets but much smaller (4-7 µm diameter compared to 1mm diameter)
Why is the micelle not absorbed across into the Intestinal cell
Destabilised as the hydrogen ions in the acid microclimate bind to the negatively charged part of the stearic acid (part of fatty acid molecule) and cause the micelle to breakdown
What does the Micelle release for diffusion across the intestinal epithelia cell
Fatty acids and monoglyceride
How can the contents of the micelle now diffuse across the Intestinal epithelial cell
As The products of fat digestion are now uncharged and lipid soluble so can cross the intestinal cell membrane
How is a dynamic equilibrium created in fat absorption
Dynamic equilibrium between fatty acids and monoglycerides in solution and in micelles
Micelle retains most products of fat digestion and constantly supply free molecules for absorption - Basically an ongoing process until all products of fat digestion are absorbed
What is the fate of product of fat digestion once the enter intestinal cells
Enter Smooth ER and are synthesised back to triaglycerol
What coats the surface of triaglycerol droplets in the intestinal cell
Amphiatic proteins
How do Triaglycerlol droplets reach and diffuse across the intestinal epithelial membrane into the extracellualr fluid
Triacylglycerol droplets transported through cell in vesicles formed from sER membrane - processed through Golgi apparatus and exocytosed
How is the products of fat digestion transported in the extracellular fluid
as a chylomicron
What is further contained in a chylomicron
contain phospholipids, cholesterol & fat-soluble vitamins
How do chylomicrons reach the blood stream
By passing into the Lacteals of the small intestine (the lymphatic vessels of the small intestine)
What are the two classes of Vitamins and examples
Fat soluble
A, D, E, K
Water soluble
B, C, and Folic acid
What class of vitamins has the same absorption pathways a products of fat digestion
Fat soluble Vitamins
A, D, E, K
How are water soluble vitamins absorbed across the small intestine
Either absorbed by passive diffusion or carrier-mediated transport.
Why cant vitamin B12 not undergo passive diffusion
Large charged molecule
How is vitamin B12 absorbed across the small intestine
Binds to intrinsic factor, forming complex and is absorbed via specific transport mechanism in distal ileum
Where is the intrinsic factor secreted from
Stomach
What is the importance of Vitamin B 12
and what can a deficiency of Vitamin B12 cause
Affects the shape of RBC, therefore affecting oxygens carrying capacity
Deficiency means RBC don’t mature properly =pernicious anemia
How is Iron transported across the brush boarder of the small intestine
DMT1 transporter
What does iron bind to intracellualrly for storage
Irons locks into a complex with ferritin
What is the pathway of unbound iron
Transports across the small intestine brush border membrane into the blood and bind with transferrin
What is the importance of biding of ingested minerals e.g. iron
Safe, as prevents the formation of oxygen free radicals
What is ferritin regulation dependant on
Dependant on how much iron you have in your body
What happens when ferritin levels increase
Hyperanemia
more iron is bound in enterocytes
What happens when ferritin levels decrease = anaemia
More iron is released into he blood
Why is to much iron in your body not of clinical importance
As around every 5 days epithelia cells will die, therefore ferritin complexes will be shed out
where in the small intestine does iron absorption occur
duodenum
