Class 3B. Digestion and Absorption

Digestion and Absorption of Proteins

Proteases

Peptidases

Digestion and Absorption of Vitamins and Metal ions

Digestion and Absorption of Carbohydrates

Digestion and Absorption of Lipids

Bile Salts

Physicochemical Properties

Function

Emulsification of lipids in food

Synthesis

Precursor

Re-absorption

also known as: Enterohepatic Circulation

Hydrolysis

Triacylglycerol = Triglyceride

Enzyme: lipase

Colipase

Phospholipids

Enzyme: phospholipases

Cholesteryl Ester

Enzyme: esterases

Absorption

Post-absorptive transport

polysaccharides

disaccharides

starch

lactose

sucrose

maltose

organs/body parts for digestion

mouth (saliva)

stomach

liver

pancreas

small intestine

colon

disaccharididase

peptidase

amylase

saliva

small intestine

maltase

sucrase

small intestine

lactase

small intestine

small intestine

polar face AND non-polar face

cholesterol - bile acids

stabilize mixed micelles

amphiphilic

saliva

pancreas

produces

lipase

amylase

amylase

lipase

bile salts

pepsin

protease

chylomicrons

simple diffusion

Because of both limited solubility and detergent properties of free fatty acids

free fatty acids need to be re-esterified to less polar products for transport in the form of lipoprotein aggregates

free fatty acids released from adipocytes are transported in plasma bound to serum albumin,

the high concentrations of free fatty acids present after a meal would overwhelm the albumin transport system.

composition

triglyceride (84%)

other lipids and proteins

cholesterol

cholesteryl ester

phospholipids

apolipoproteins

absorbed towards the end of ileum of small intestine

carried in portal blood, bound to albumin

added to bile again by liver and secreted again through gallbladder

pepsin

site-specific cleavage

trypsin

chymotrypsin

elastase

activated from pepsinogen by HCl

activated from trypsinogen

activated from chymotrypsinogen

activated from proelastase

aminopeptidase

carboxypeptidase

fat soluble vitamins

minerals

Regulation of digestion

gastrin

cholecystokinin

secretin

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