Question

Based on the figure, describe the mechanisms of uptake of amino acids from the intestinal lumen into an intestinal cell and then from the intestinal cell to the bloodstream.

Your answer should include the following terms: primary active transport, secondary active transport, electrochemical gradient, concentration gradient, facilitated diffusion, energy.

Question 2. The image below depicts the transport mechanisms used by your intestinal cells to absorb amino acids from your food into your bloodstream. Nat Intestinal lumen Amino acid Nat Amino acid Na SATP ADP Facilitated diffusion transporter Portal vein Amino acid

Answer 1

Intestinal lumen surface is large compared to inside the cell,so the aminoacids that are in the intestine lumen concentration is less compared to inside the cell.Now for these aminoacids to move inside the cell,they have to move against their concentration gradient.For this to get accomplished they make use of SECONDARY ACTIVE TRANSPORT where there is no direct involvement of ATP as energy,rather the form of energy involved here is DOWN THE CONCENTRATION GRADIENT of SODIUM IONS.Down the concentration gradient movement by sodium ions inside the cell releases energy,this energy is used by aminoacids to get themselves transported against their concentration into the intestinal cell.

AMINO ACIDS that are inside the intestinal cell are now in higher concentration compared to blood concentration of aminoacids.They now are to be transported down the concentration gradient,I.e passive movement.Here they move by facilitated diffusion form of passive transport.

Electro chemical gradient of sodium ions is generally, that sodium ions are more outside the cell,while potassium ions are more inside the cell.To maintain this gradient sodium ions that moved inside the cell along with aminoacids are to be now transported outside the cell.To get this job done ions make use of Na/K pump.Here there is a use of ATP as energy source,where potassium ions come inside and sodium ions transported outside the cell to maintain the electrochemical gradient.