Active Transport Flashcards
What does primary active transport use?
Directly uses energy from breakdown of ATP
What does secondary active transport use
Energy stored in ion concentration gradients created by primary AT - indirectly uses ATP.
What is an example of primary AT and what does it do and how?
Sodium Potassium Pump. Takes Sodium out of the cell and brings potassium in. There is an active site where the Na+ or K+ molecules can bind to, as well as an ATP molecule bonded to the actual carrier. The ATP is broken down which not only supplies energy, but changes the shape of the ATP molecule, making the carrier flip over to face the opposite direction and hence carry out the molecule. The molecule on the other side of the membrane (be it Na+ or K+) can now bind to the carrier, for the second phosphate to be released, spinning the carrier back and releasing the molecule.
How many Na+ molecules compared to K+ molecules are transported by the Na+ - K+ Pump?
3 sodium, 2 potassium
How does secondary active transport work?
Relies on another molecule (usually an ion) to go with its concentration gradient. The gradient itself provides the energy needed to move the molecule of interest against ITS concentration gradient.
the molecule of interest is almost “hitching a ride” as if the gradient was a current
How does secondary AT indirectly use ATP?
It relies on primary AT to transport Na+ (for example) against its concentration gradient, so secondary AT can then use it to transport other molecules like glucose.
what is vesicular transport and what are the two types?
the active transport of large substances / transfer of material between the ECF and ICF within vesicles.
endocytosis - from ECF to ICF (into cell)
exocytosis - from ICF to ECF (out of cell)
Three types of endocytosis
- Receptor mediated endocytosis - triggered by the binding of the wanted molecule to a receptor on the plasma membrane. Takes in both receptor and molecule of interest, which seperate when in the cell
- pinocytosis - uptake of ECF by the cell (cell drinking)
- phagocytosis - uptake of solid objects such as bacteria or cellular debris (cell eating)
Explanation of exocytosis
Requires a secretory vesicle (for example one filled with hormones) released from the Golgi (from inside the cell) which attached to the cell membrane and becomes part of it, releasing its molecules out into the ECF.
