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IBDP Biology- Absorption in Digestion

Topic 6.2- Food Absorption in Body

· Biology,Digestion,IBDP BIOLOGY

In order to fully gain the nutrients attained from the food we ingest, the body must absorb it. In this IBDP Biology post, we will understand:

  • The different ways in which the body absorbs different molecules
  • Villi and Microvilli
  • Modes of absorption

Absorption 

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Absorption happens using the Villi and Microvilli

Villi are:

  • finger-like projections
  • increase 
  • surface are
  • a for absorption
  • Epithelial cells with many 

mitochondria

Villi: Many folds of the inner cells lining the small intestine

Each villus contains:

  • Capillary 

Bed for absorption and transportation

  • Lacteal

(vessel of lymphatic system) to absorb larger monomers (fatty acids)

Adaptations for absorption:

  • Many villi potrude into the lumen greatly increasing the surface area for absorption
  • Single cell layer of epithelial cells - short path for diffusion
  • Micro villiof the surface of each cell increase surface area even more
  • Capiliries are close to epithelium - short path for diffusion, rich supply of blood
  • Rich blood supply maintains concentration gradient between lumen and blood 

Transport mechanisms for Absorption 

Lipids

  • Simple Diffusion: 
  • Nutrients pass down the concentration gradient between phospholipids in the membrane
  • Hydrophobic nutrients fatty acids and monoglycerides

Fructose and Vitamins

  • Facilitated Diffusion: 
  • Nutrients pass down the concentration gradient through specific channel proteins in the membrane
  • Hydrophillic nutrients fructose

Mineral ions

  • Active Transport: 

Nutrients are pumped through the membrane against the concentration gradient by specific pump proteins eg. Sodium, calcium and iron

Tryglycerides and cholesterol in lipoprotein particles

  • Endocytosis:

 In which small droplets of fluid are passed through the membrane by means of vesicles  

Dialysis tubing to model Absorption 

In IBDP Biology, Dialysis tubing can be used to model absorption by the epithelial cells of the small intestine

The tubing is semi-permeable and contains pores 1 - 10 nm in diameter

Cola drinks contain a mixture of substances that models digested and undigested food in the intestine

The water surrounding the bag is tested at different intervals to see if substances in the cola have diffused through the dialysis tubing

Test solutions inside and outside dialysis tubing for starch and glucose before and after 15 minutes

Expected Result: Glucose and phosphoric acid [contain small-sized particles] diffuse through the tubing but caramel [contains larger polymers of sugar] does not

And that's the end!

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Want to Boost Up Your IB Biology? Check out our study tips here!

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References:

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.sciencelearn.org.nz%2Fimages%2F2259-villi-in-the-small-intestine&psig=AOvVaw0fLAFUZPaY7Qg7dcBiHCH-&ust=1625294823137000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCNDbh5flw_ECFQAAAAAdAAAAABA3

Drafted by Venetia (Biology)

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