Topic 2b- exchange across cell membranes- active transport Flashcards
What is active transport?
Uses energy to move molecules and ions across membranes, usually against concentration gradient.
How are carrier proteins involved in active transport?
A molecule attaches to the carrier protein, the protein changes shape and this moves the molecule across the membrane, releasing it on the other side.
Differences between active transport and facilitated diffusion?
Active transport moves solutes from low to high concentration. Whereas facilitated diffusion is high to low.
Active transport requires energy, facilitated diffusion does not.
What do co- transporters do?
They bind two molecules at a time.
The concentration gradient of one of the molecules is used to move the other molecule against it’s own concentration gradient.
What factors affect rate of active transport?
Speed of individual carrier proteins, number of carrier proteins present, rate of respiration in the cell and the availability of ATP.
Glucose enters the ileum epithelium ( final part of the small intestine) with sodium ions.
Explain how.
Sodium ions are actively transported out of the ileum epithelial cells, into the blood, by the sodium- potassium pump. Creates a concentration gradient.
This causes sodium ions to diffuse from the lumen of the ileum into the epithelial cell, down their concentration gradient. They do this via sodium-glucose co- transporter proteins.
Co- transporter carries glucose into the cell with the sodium. As a result the concentration of glucose inside the cell increases.
Glucose diffuses out of the cell, into the blood, down it’s concentration gradient through a protein channel, by facilitated diffusion.
