Flashcards in 1: Active Transport Deck (21):
Define 'active transport'.
the movement of substances across membranes using energy from ATP
What can active transport do that diffusion cannot?
move substances against the concentration gradient - from a region of lower concentration to a region of higher concentration
What are protein pumps in the membrane used for?
How many different substances can a protein pump transport? How, then, do cells control what is absorbed and what is expelled?
- one substance only
- by changing the type of protein pump
How many different directions do protein pumps work? What does this mean for the substance?
- one specific direction
- substance can only enter the pump on one side and only exit on the other side
Draw and label a diagram of a protein pump transporting a particle. (p12)
1. particle enters the pump from the side with a lower concentration
2. particle binds to a specific site. Other types of particle cannot bind.
3. Energy from ATP is used to change the shape of the pump.
4. Particle is released on the side with a higher concentration and the pump then returns to its original shape.
Where can sodium-potassium pumps be found? What do they do?
- found in the axons of neurons
- moves sodium ions and potassium ions across the membrane
In a sodium-potassium pump: which direction are sodium and potassium ions pumped (relative to each other)? What, therefore, is the technical term for this sort of pump?
- opposite directions
- an antiporter
How is the energy required for pumping sodium and potassium ions in a sodium-potassium pump obtained? What therefore is this type of reaction called?
- by converting ATP --> ADP and phosphate
- an ATPase (or Na+/K+ -ATPase)
In a sodium-potassium pump, how much energy does one ATP provide?
- enough energy to pump two potassium ions in and three sodium ions out of the cell
What does the pumping of potassium ions and sodium ions in a sodium-potassium pump achieve? Why is this necessary?
- a concentration gradient between the inside and outside of the neuron
- needed for the transmission of nerve impulses in axons
What is situated in the centre of a sodium-potassium pump?
5 binding sites:
- 2 binding sites for K+ ions
- 3 binding sites for Na+ ions
How many states does a sodium-potassium pump have? How does the sodium-potassium pump change states?
- two alternate states
- using energy from ATP
Describe the two alternate states in a sodium-potassium pump.
- access to binding sites from outer side of membrane
- stronger attraction to K+ ions, so Na+ ions are discharged from the cell an K+ ions bind.
in the other:
- access to binding sites from the inside of membrane
- stronger attraction to Na+ ions, K+ ions discharged
What does fluidity of membranes allow them to do?
move and change shape
small piece of the plasma membrane can be pinched off to create a vesicle containing some material from outside the cell
What is the opposite of endocytosis? Outline the opposite of endocytosis.
- vesicles move to the plasma membrane and fuse with it, releasing the contents of the vesicle outside the cell
What are vesicles in a cell used for? Give an example.
- used to move materials from one part of the cell to another
- vesicles move proteins from the RER to the Golgi apparatus
Draw a diagram showing the process of endocytosis. (p12)
Draw a diagram showing the process of exocytosis. (p12)