Topic 3- Absorption Flashcards
What is the mechanism for the absorption of monosaccharides and amino acids?
Co- transport
Specific amino acid 1.____ ____ ______ (carrier molecules) are found within the cell-surface membrane of the 2.____ ___ in the ileum
- co-transport proteins
2.epithelial cells
What also has to be present for amino acids to be transported?
Sodium ions
For every 1.____ _____ that is transported into the cell, an 2._____ ____ is transported in
- sodium ion
- amino acid
How does co- transport occur
-Faccilitated diffusion
-Movement of molecules down their concentration gradient
Describe the process of absorption of amino acids
-Amino acids diffuse across the epithelial cell and then pass into the capillaries via facilitated diffusion
-The concentration gradient of sodium ions from the lumen of the ileum into the epithelial cell is maintained by the active transport of sodium ions out of the cell and into the blood via a sodium-potassium pump at the other end of the cell
How are micelles formed?
monoglycerides and fatty acids associate with phospholipids and bile salts
Describe the process of absorption of monosaccharides
-Sodium ions and glucose molecules are co-transported into the epithelial cells via facilitated diffusion
-The glucose molecules diffuse across the epithelial cell and enter the capillary at the other end of the cell by facilitated diffusion
-the concentration gradient of sodium ions is maintained by actively transporting sodium ions out of the epithelial cells into the blood
Why are micelles formed?
Monoglycerides and fatty acids are not very soluble
Why are freely dissolved molecules (monoglycerides and fatty acids) able to diffuse through the phospholipid bilayer?
They are non polar
What is the first step of the absorption of lipids?
-micelles break down and add to a pool of fatty acids and monoglycerides that are dissolved in the small intestine solution
-freely dissolved molecules enter the epithelial cell by diffusion
What is the 2nd step of the absorption of lipids
How can short fatty acid chains within the epithelial cells move directly into the blood?
Via diffusion
How do longer fatty acid chains move into the blood?
recombine with monoglycerides and glycerol to form triglycerides in the endoplasmic reticulum
The triglycerides are packaged into lipoproteins called what?
chylomicrons
