active transport Flashcards
What is the definition of active transport?
Active transport uses energy to move molecules and ions across plasma membranes, usually against a concentration gradient.
what is involved in active transport ?
Carrier proteins and co-transporters
how do carrier proteins and active transport work ?
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.
what are the two main differences between active transport and facilitated diffusion ?
Active transport usually moves solutes from a low to a high concentration — in facilitated diffusion, they always move from a high to a low concentration.
Active transport requires energy — facilitated diffusion does not.
why is ATP important for active transport ?
ATP (a molecule produced by respiration) is a common source of energy in the cell, so it’s important for active transport. ATP undergoes a hydrolysis reaction, splitting into ADP and Pi (inorganic phosphate). This releases energy so that the solutes can be transported.
where is glucose absorbed into the blood stream ?
the small intestine.In the mammalian ileum (the final part of a mammal’s small intestine) the concentration of glucose is too low for glucose to diffuse out into the blood. So glucose is absorbed from the lumen (middle) of the ileum by co-transport.
how is glucose absorbed into the blood stream by co transport ?
Sodium ions are actively transported out of the epithelial cells in the ileum, into the blood, by the sodium-potassium pump. This creates a concentration gradient — there’s now a higher concentration of sodium ions in the lumen of the ileum than inside the cell.
This causes sodium ions to diffuse from the lumen of the ileum into the epithelial cell, down their concentration gradient. They do this via the sodium-glucose co-transporter proteins. The 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 its concentration gradient through a protein channel, by facilitated diffusion.
what are the factors affecting active transport ?
the speed of individual carrier protiens
the number of carrier proteins present
The rate of respiration in the cell and the availability of ATP.
how does the speed of individual carrier proteins affect the rate of active transport ?
the faster they work, the faster the rate of active transport.
how does the number of carrier proteins present affect the rate of active transport ?
the more proteins there are, the faster the rate of active transport.
how does the the rate of respiration in the cell and the availability of ATP affect the rate of active transport ?
If respiration is inhibited, active transport can’t take place.
what type of process is active transport ?
an Active process
