Co-transport In The Ileum

Question 1

how do you increase the rate of movement across membranes of epithelial cels?

Answer 1

• microvilli which project from the cell surface membrane to provide more surface area for carrier proteins

Question 2

what is the role of diffusion in absorption?

Answer 2

• as carbohydrates and proteins are being digested continuously there is normally a greater concentration of glucose and amino acids within the ileum than in the blood
• this means there is a concentration gradient down which glucose moves by facilitated diffusion from inside the ileum into the blood
• given that the blood is constantly being circulated by the heart
• the glucose absorbed into it is constantly being removed by the cells as they use it up during respiration
• this helps to maintain the concentration gradient

Question 3

what is the role of active transport in absorption?

Answer 3

• diffusion results in equilibrium
• so not all glucose and amino acids can be absorbed.
• co transport allows these to be absorbed from the small intestine

Question 4

how does the sodium potassium pump work?

Answer 4

• sodium ions are actively transported out of epithelial cells by the sodium potassium pump into the blood
• this helps maintain a higher concentration of sodium ions in the lumen of the intestine than inside the epithelial cells
• sodium ions diffuse into the epithelial cells down this concentration gradient through a protein carrier in the cell surface membrane
• as the sodium ions diffuse through a carrier protein with either amino acid molecules into the cell with them