3 - Active Transport and Co-transport

What is the definition of active transport?

the movement of molecules against the concentration gradient that requires energy (ATP) using trans-membrane proteins

How is active transport different from passive transport?

active transport requires energy and moves against a concentration gradient, while in passive transport there is no need for energy and moves a concentration gradient

What is the definition of co-transport?

the transport of one substance is coupled with the transport of another substance across a membrane.

What is step 1 of co-transport?

- glucose formed after digestion

- high concentration of glucose in lumen

What is step 2 of co-transport?

- Na+ ions move down concentration gradient via facilitated diffusion to epithelial cells

- Na+ ions and glucose bind to protein, 2 Na+ ions and 1 glucose must bind before being transported across membrane

What is step 3 of co-transport?

- glucose moves into blood plasma via a uniporter by facilitated diffusion

What is step 4 of co-transport?

- Na+ ions actively transported out of epithelial cells through a protein carrier molecule (antiporter)

- maintains concentration gradient between lumen and epithelial cell in step 1