4.5 Co-transport Flashcards
What effect do microvilli have on the rate of movement across membranes?
They line the epithelial cell providing more surface area for the insertion of carrier proteins, so that diffusion, facilitated diffusion and active transport can take place.
How does diffusion take place in absorption?
There is a greater concentration of glucose and amino acid within the ileum than in the blood therefore, there is a concentration gradient down which glucose moves by facilitated diffusion from inside the ileum into the blood. As the blood is constantly being circulated, the glucose absorbed into it is continuously being removed by the cells as they use it up during less respiration which helps maintain the concentration gradient between the ileum and the blood.
How is a glucose molecule can transported through the sodium potassium pump
~ sodium ions are actively transported out of the epithelial cells into the blood by the sodium potassium pump ( takes place in a carrier molecule ) - this creates a concentration gradient as there is a higher concentration of sodium ions in the lumen of the ileum, then inside the epithelial cell.
~ sodium ions diffuse from the lumen of the ileum into the epithelial cell down this concentration gradient they do this through the sodium-glucose co-transporter proteins.
~ this protein carries glucose into the cell with sodium sodium concentration of glucose in the cell increases
~ glucose diffuses out of the cell into the blood down the concentration gradient by facilitated diffusion (using a different protein)
How do sodium ions and glucose molecules differ in the way of being transported into the cell?
~ the sodium ions move down their concentration gradient
~ the glucose molecules move against their concentration gradient
What are co-transporters?
~ a type of carrier protein, which binds to 2 molecules at a time
~ they work by creating a concentration gradient of one of the molecules to move the other molecule against its own concentration gradient
