The structural features of villus cell
Microvilli: increase surface area of plasma membrane, allowing for more absorption of digested food materials. The membrane is embedded with digestive enzymes and channels to assist in uptake.
Mitochondria: Provide energy (ATP) for active transport processes.
Pinocytotic vesicles: Contain fluid and dissolved food materials from the lumen of the ileum.
Tight junctions: Occluding associations between the membrane of two adjacent cells, creating an impermeable barrier to keep digestive fluids separate from tissue fluids and ensure a one way flow
How the ileum absorbs and transports food
- Lipids are absorbed by simple diffusion (can pass freely through hydrophobic core of the plasma membrane).
- Channel proteins help hydrophilic food molecules pass through the hydrophobic portion of the phospholipid bilayer. Water-soluble molecules (e.g. fructose), minerals and vitamins are absorbed by facilitated diffusion.
- Protein pumps in the plasma membrane hydrolyse ATP to translocate molecules against the concentration gradient. Glucose, amino acids and mineral ions are all absorbed by active transport.
- Endocytosis involves the invagination of the plasma membrane to create an internal vesicle containing extracellular materials.
- Each pinocytotic vesicle contains a small droplet of fluid from the lumen of the ileum.
- The vesicles contain channels and pumps from the plasma membrane and so digested food can be absorbed from the vesicle into the cytoplasm.
That is all for this post!
Drafted by Venetia (Biology)