Absorption Flashcards
How does having a shirt diffusion pathway affect absorption in the ileum
Each villus has a single layer of epithelial cells
How is a concentration gradient marinated when absorption occurs in the ileum?
-Rich supply of blood capillaries to take away glucose and amino acids immediately from the epithelial cells
- Lymph vessels carry lipids away maintaining low concentration
- Food moving through the gut maintains high concentration
How is a large surface area achieved when absorption in the ileum occurs?
Long length of ileum
Villi
Epithelial cell had microvilli (folds in the cell surface membrane)
Why effect does a large number of carrier proteins have on absorption in the ileum?
Increases permeability by facilities diffusion and active transport
What effect does a large number of mitochondria have on absorption in the ileum?
Releases energy through aerobic respiration for ATP used for active transport
How do glucose and amino acids enter epithelial cells?
Facilitated diffusion
Active transport
Together known as co-transport
How does co-transport work?
Sodium moves from a higher concentration in the lumen to a lower concentration inside the epithelial cell
As it moves, glucose moves in with it (by cotransport through a carrier protein called a symport)
To keep glucose coming in we need to keep a low concentration of sodium in the cell
How are sodium ions transported out of the cell
Transported out of the epithelial cells into the blood
By active transport
Through the sodium potassium pump which uses ATP
This creates and maintains a concentration gradient for sodium
How do sodium ions enter the cell?
Sodium ions move down the concentration gradient from the lumen of the ileum to the epithelial cells
This occurs through a carrier/symport proteins
Glucose is also brought into the cell
Glucose travels into the blood capillaries by facilitated diffusion
Without ATP the sodium conc gradient wouldn’t exist and the sodium glucose carrier protein wouldn’t function
What are the 2 main parts of absorption of lipids
Movement from the lumen of the lumen to the epithelium
Movement across the epithelium to the blood
how do lipids move from the lumen of the ileum to the epithelium
Monoglycerides/fatty acids aren’t soluble so they react with bile salts and phospholipids
This produces micelles —> these are smaller than emulsion droplets
Micelles transport the monoglycerides/fatty acids to the surface of epithelial cells for absorption
Micelles break down next to the epithelial cell
How do lipids move from across the epithelium to the blood?
Micelles break down next to the epithelial cell
Fatty acids and monoglycerides are released
These diffuse through the phospholipid bilayer of microvilli
Glycerol and fatty acids in the lumen enter the epithelial cells by diffusion
They recombine into a triglyceride in the SER
Triglycerides are coated with proteins to form a chylomicron by the golgi
Chylomicrons enter lacteals (lymphatic vessels) by diffusion before draining into the blood
How does chylomicrons enter the lymphatic vessels
Glycerol and fatty acids in the lumen enter the epithelial cells by diffusion
They recombine into a triglyceride in the SER
Triglycerides are coated with proteins to form a chylomicron by the golgi
Chylomicrons enter lacteals (lymphatic vessels) by diffusion before draining into the blood
How are digested lipids absorbed
Monoglycerides/fatty acids form micelles with bile salts
Micelles move to the surface of epithelial cells
They diffuse through the epithelial cell mebrsne
Short fatty acids diffuse into the blood directly
Chylomicrons form
The chylomicrons are absorbed into lacteals and drain into the blood
