Co-Transport and Absorption of Glucose in the Ileum Flashcards
What is the significance of the microvilli that are possessed by the epithelial cells lining the ileum?
The microvilli provide a brush border which effectively provides more surface area for insertion of carrier proteins for diffusion, facilitated diffusion, and active transport can take place.
How is the rate of movement by facilitated diffusion across epithelial cell-surface membranes increased?
The constant circulation of blood allows glucose to move down the concentration gradient from inside the ileum into the blood, and then continuously removed from cells as it circulates the body to be used up in respiration. This helps to maintain the concentration gradient between the inside of the ileum and the blood.
Why are glucose and amino acids also absorbed by active transport?
So that all glucose and amino acids can be absorbed into the blood without passing out of the body and being wasted.
What is the mechanism that actively transports glucose and amino acids?
Co-transport. This is because either glucose or amino acids are drawn into the cells along with sodium ions, which have been actively transported out by the sodium potassium pump.
How is a high concentration gradient of sodium ions in the lumen of the intestine than inside the epithelial cells maintained?
Sodium ions are actively transported out of epithelial cells by the sodium-potassium pump into the blood, taking place in a protein carrier molecule.
How does the high concentration gradient of sodium ions allow glucose molecules or amino acids to be transported?
Sodium ions diffuse into epithelial cells down the concentration gradient through a co-transport protein in the cell-surface membrane. As sodium ions diffuse in through this second carrier protein, either glucose molecules or amino acids are carried into the cell with them.
How do glucose/amino acids then pass into the blood plasma out of the epithelial cells?
By facilitated diffusion using another type of carrier.
What powers the movement of glucose and amino acids into the cells?
The sodium ion concentration gradient rather than ATP directly, powers the movement. This makes it and indirect, rather than direct form of active transport.
