Lecture 4: Ion Channels Flashcards
Refresher: Ions ____ cross the synthetic lipid bilayer
cannot
Ion channels are ____ and ____.
Gated and selective
Note that gated refers to (opening = regulated)
How are ion channels selective?
selective for a specific ion (size and charge)
How does the selectivity filter work?
arrange molecules to pass in a single file
With the selectivity of ion channels, there is no actual ion ______ site as seen in carriers
binding
What can a dysfunctional Na channel lead to?
Seizures
Name the two seizure disorders involved in dysfunctional sodium channels
- Genetic epilepsy with febrile seizures (GEFS+)
2. Dravet Syndrome (severe myoclonic epilepsy of infancy)
What kind of subjects serve as a model to study epilepsy?
Flies, as they have the only voltage-gated sodium channel ? idk wtf that means,
the domain organization is conserved
regions para that are critical for function are conserved
Ion channels only mediate _____ transport (down the electrochemical gradient)
Passive
Ion channels have no ______ _____ ___ or _____.
- Specific binding site
2. Vmax
What must be taken into consideration when selecting a model system?
- costs
- ability to observe
- complexity
- time
Best option is using a simple system that allows a scientist to study a particular process
- Which of the following conditions would most likely promote the flow of sodium ions into the cytoplasm of a cell?**
A: If the electrochemical gradient for sodium was reversed
B: If Na+/ K+ pumps were prevented from binding ATP
C: If Na+/ K+ pumps were prevented from hydrolyzing ATP
D: If a voltage-gated sodium channel was opened
E: Any of the above could allow Na+ ions to enter the cytoplasm of a cell
D
- A point mutation in the ligand binding site of a Na+ channel will most likely
A: turn a Na+ channel into a K+ channel
B: have no effect
C: turn this ligand-gated channel into a voltage gated channel.
D: prevent channel opening in the presence of the ligand
E: prevent channel closing
B
