Co-transport and the absorption of glucose in the ileum Flashcards
What do the epithelial cells lining the ileum possess?
Microvilli (finger-like projections of the cell-surface membrane)
What are microvilli collectively termed as?
A brush border.
Why do epithelial cells have microvilli?
To provide more surface area for the insertion of carrier proteins through which transport can take place.
Apart from microvilli, name and describe another mechanism that increases transport across the epithelial cells in the ileum.
To increase the number of protein channels and carrier proteins in any given area of the membrane (increase density).
Why is there a greater concentration of glucose glucose and amino acids within the ileum than the blood?
Carbohydrates and proteins are being digested continuously.
How does the glucose move into the blood?
Via facilitated diffusion.
How is the concentration gradient (glucose) maintained between the blood and the ileum?
The glucose absorbed is constantly removed by cells that use it up in respiration, this means the rate of movement by facilitated diffusion across epithelial cell-surface membranes is increased.
Why aren’t glucose and amino acids transported by diffusion?
Diffusion results in a dynamic equilibrium which means that not all available glucose and amino acids would be absorbed, instead they are actively transported, by a mechanism called co-transport.
Why is co-transport used to describe the absorption of glucose and amino acids?
because either amino acids or glucose are drawn into the cell along with sodium ions that have been actively transported out by the sodium-potassium pump.
Explain the process of co-transport of the glucose molecule.
Sodium ions are actively transported out, this takes place in a carrier protein. Sodium ions diffuse back in and carry glucose/amino acids into the cell with them. The glucose/ amino acid passes into the blood plasma by facilitated diffusion using another type of carrier.
