fat digestion + absorption, bile acids

define digestion

Enzymatic process where food is broken down to smallest absorbable units (amino acids, simple sugars, fatty acids)

define absorption

transfer of digested food components across absorptive surface of gastrointestinal tract

define metabolism

various pathways nutrients take often digest+absorp.

• “where are they going and what are they used for?”

where is fat digested and absorbed?

in the small intestine

what is the first step for fat digestion/absorption

1. triglycerides enter small intestine

what is the second step for fat digestion/absorption

2. bile acids (from liver) enter and disperse fat into smaller droplets (emulsification)

what is the third step for fat digestion/absorption

3. pancreas releases lipases: enzymes that clip off fatty acids from triglyceride backbone

what is the fourth step for fat digestion/absorption

formation of micelles (water+oil mix)

what is the fifth step for fat digestion/absorption

fatty acids + monoglycerides absorbed into intestinal cell

what happens when f.a is less than or equal to 12C

• it is absorbed directly into blood

• (vascular system/portal vein)

if f.a is greater or equal to 14C

• reformation of triglyceride

• (PACKAGED INTO CHYLOMICRON)

• enters the lymphatic system → thoracic duct → enters blood stream

what are bile acids made from

made from cholesterol in liver

what do bile acids require

• fat to:

  • emulsify

  • form micelles

amount of bile acids required each day are larger or smaller than the amount made by liver?

• larger!

• it is reabsorbed and recycled

what is the role with soluble fibre in terms of maintaining healthy blood cholesterol levels?

• it binds to cholesterol and bile acids so u can poop it out

• this then makes the liver make more bile acids from freshly-made cholesterol (which is labour intensive) or already made cholesterol = lowers blood cholesterol levels

enterohepatic circulation

the movement of bile acids from the liver to the small intestine and back to the liver