Lecture 09 Flashcards
How does the architecture of aquaporins allow passage of water ?
- pore is lined with hydrophilic amino acids on one side and hydrophobic amino acids on the other side
- pore is too narrow to allow hydrated ions to pass through
molecular relay mechanism
rapidly moving protons exist as hydronium ions in water
Asparagine (N) amino acids lining aquaporin
prevents molecular relay because 2 asparagine molecules occupy both valances of the O2 of the central water molecule
How are ion channels selective?
selectivity filter
selectivity filter
narrow opening that allows ions of certain size and charge to pass through
How are ion channels gated?
different stimuli causes ion channels to open
In plants and fungi, how is the membrane potential established?
ion pumps in many cells
In mitochondria, how is membrane potential established?
organelles
What has the biggest contribution to resting membrane potential in animal cells?
K+ leak channels
What has the biggest contribution to resting membrane potential in animal cells?
K+ leak channels
Mechanosensitive channels respond to?
- external stimuli (sound touch pressure
2. internal stimuli (osmotic pressure, membrane bending)
Voltage gated cation channels
- allow action potentials to propagate along axon without attenuation
- all electrically excitable cells express them (neurons, muscle cells, endocrine cells, egg cells)
Features of voltage gated cation channel
- voltage sensor
- selectivity filter
- inactivation gate
Lateral portal of VGCC
access to hydrophobic drugs to enter and block ion conductance (such as anesthetics)
The action potential
→ Voltage-gated Na+ channels potentiate membrane depolarization (positive feedback) → Refractory period prevents action potential from running backwards → Voltage-gated K+ channels aid the repolarization
