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I am looking for examples of colloids involved in digestion for a cross-curricular (bio-chem-physics) lesson plan. Although I have found references implicating colloids in both lipid and protein digestion, I haven't been able to identify which colloids they are speaking of. Can someone provide specific examples?

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Fat released from food will form macroscopic lipid droplets in the aqueous environment of the gut. In the small intestine, bile synthesised by the liver is secreted into the lumen via the bile duct. Bile contains bile salts which act as detergents to disperse the lipid droplets by forming micelles. I think this dispersion of micelles could be described as a colloid.

I have no idea what the reference to protein digestion could mean, although some hydrophobic proteins might become associated with the micelles that I've already described, and I imagine that bile salts might help to solubilise protein aggregates in the gut lumen by direct interaction - they, or their derivatives, are sometimes used by protein biochemists as detergents for protein solubilisation (e.g sodium deoxycholate.

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