Social cells 2: ion channels Flashcards
Passive Transport
Transport that does not require ATP, e.g just diffusion through the bilayer or through protein channels (or facilitated diffusion)
What is an example of a molecule that needs a carrier protein?
Glucose
What are the limitations of facilitated diffusion?
Transport mechanism is specific
- Limited capacity
- Transport can be affected by competition
What is Active transport?
Carrying molecules across a membrane using ATP (against the concentration gradient)
What are the two mechanisms of active transport?
Primary and Secondary
What does Uniporter mean?
One direction
What does Symporter mean?
2 ions in the same direction
What does Antiporter mean?
Multiple ions in different directions
What is an example of primary transport?
Sodium
What is an example of secondary active transport?
Glucose in the proximal distal tubule being taken up with sodium.
Main notes about calcium pumps?
The cytosolic concentration needs to be kept low, and it uses ATP
How do Ligand-Gated Channels work?
A ligand or messenger binds to the channel which causes a conformational change to the channel allowing ions to move through
What is an example of a ligand-gated channel?
GPCR which can pull potassium channels into an ‘open’ state
What is the GPCR channel in skeletal muscle called?
NACH receptor at neuromuscular junctions
How do Voltage-gated channels work?
Change in voltage/ Depolarisation causes the channel to open
How do leak channels work?
A pore in the membrane so they are always open, allows for movemnt of ions down conc gradient
How do Stretch activated channels work?
Change in tension (Bilayer model) causes a conformational change in the membrane which pulls apart the channel
How does the Tether model work?
They are anchored to the cytoskeleton, tension in the cytoskeleton causes the channel to be pulled open
What are channels involved in?
- Muscle paralysis
- Heart disease
- Local anaesthetics
Resting Membrane potential
the potential across the membrane when there is no action potential
being propagated
What is an example of a leak channel?
potassium leak channel
What is an example of a stretch-mediated channel?
Calcium activated potassium channel
What does the Nernst equation determine?
The flow of individual ions across a membrane
