Chapter 2

1. 1Ion channels are:
   
   
   

   1. Aa) temporary openings (pores) in the cellular membrane;
   2. Bb) membrane proteins that span across the lipid bilayer and come in contact with the extra- and intracellular environments;
   3. Cc) mobile membrane proteins that move across the lipid bilayer from the extracellular into the
      intracellular space.
2. 2What is the role of the electrostatic filter in ion channels?
   
   
   

   1. Aa) it changes the ion channel state: open or closed;
   2. Bb) it selects the ion species that can pass through the channel;
   3. Cc) it interacts with the electrically charged heads of the phospholipid molecules in order to change conformation.
3. 3Is it possible for Clions to pass through a Ca2+
   ion channel?
   
   
   

   1. Aa) no, because Clions are too large to fit the narrow channel;
   2. Bb) yes, they can;
   3. Cc) no, because the Ca2+ ion channel has an electrostatic selectivity filter with negative charge.
4. 4How many gates do voltage-gated Na+
   channels have?
   
   
   

   1. Aa) one;
   2. Bb) two;
   3. Cc) three.
5. 5Which of the following membrane conditions activate the voltage-gated (potential-dependent) ion
   channels?
   
   
   

   1. Aa) depolarization of the plasma membrane;
   2. Bb) hyper-polarization of the plasma membrane;
   3. Cc) keeping the membrane potential unchanged for period of 50 ms.
6. 6Which of the following combinations of factors determine the activation time of the voltage-gated
   ion channels?
   
   
   

   1. Aa) the membrane potential and the pH of the cytosol;
   2. Bb) the level of hyper-polarization of the membrane and the specific channel gate kinetics;
   3. Cc) the level of membrane depolarization and the specific ion channel kinetics.
7. 7What activates ligand-gated (receptor-regulated) ion channels?
   
   
   

   1. Aa) changes in the membrane potential;
   2. Bb) interaction between the corresponding ligand and the receptor, regulating the ion channel;
   3. Cc) the process of internalization of the receptor
8. 8What prevents inorganic ions from moving through the phospholipid membrane?
   
   
   

   1. Aa) the equal concentrations of ion species on both sides of the membrane (isotonicity);
   2. Bb) inorganic ions are water-soluble. The phospholipid bilayer does not permit the passage of watersoluble substances;
   3. Cc) the ion passage is prevented by the higher hydrostatic pressure inside the cell.
9. 9. Are ion channels completely impermeable for all but the ion species that give the channel’s name?
   
   
   

   1. Aa) no, other similar ions can pass with low probability;
   2. Bb) yes, they permit only the ion species that give the channel’s name;
   3. Cc) no, large organic molecule can also pass through the channels.
10. 10Is ion channel traffic regulated and how?
    
    
    

    1. Aa) no, ion traffic is not regulated;
    2. Bb) ion traffic is regulated through conditional gating mechanisms;
    3. Cc) ion traffic is regulated by pressure gradients.

11. 11. Which of the following descriptions refers to ion channels?
    
    

    1. Aa) a random, temporary formation of pores in the lipid bilayer;
    2. Bb) protein structures that transport ions across the membrane with the expense of energy;
    3. Cc) protein structures that allow passive transport of inorganic ions.
12. 12Choose the best fitting description for ion channels from the following:
    
    
    

    1. Aa) membrane protein structures that span across the membrane, and under certain conditions provide selective ion transport between extra and intra cellular spaces;
    2. Bb) membrane lipid structures that span across the membrane, and under certain conditions allow a water-filled passage between extra and intra cellular spaces;
    3. Cc) membrane protein structures that provide uninterrupted ion transport between intra and extra cellular spaces.
13. 13What forces drive ions through the ion channels?
    
    
    

    1. Aa) electrochemical gradients;
    2. Bb) hydrostatic pressure;
    3. Cc) osmotic pressure.
14. 14What type of transport takes place through ion channels when they are activated:
    
    
    

    1. Aa) passive;
    2. Bb) active;
    3. Cc) passive when moving in, and active when moving out of the cell.
15. 15Which ion types can pass through the calcium-activated potassium channels?
    
    
    

    1. Aa) calcium ions;
    2. Bb) potassium ions;
    3. Cc) sodium ions.
16. 16Depolarization of the plasma membrane activates this type of ion channels:
    
    
    

    1. Aa) receptor-regulated (ligand-gated) channels;
    2. Bb) voltage-gated channels;
    3. Cc) none of the above.
17. 17Nifedipine and Verapamil are channel blockers for this type of ions:
    
    

    1. Aa) calcium membrane channels;
    2. Bb) sodium channels located on cellular organelles;
    3. Cc) potassium membrane channels.
18. 18The repolarization phase of spike potentials is due to the opening of this type of channels:
    
    
    

    1. Aa) calcium-activated potassium channels;
    2. Bb) voltage-gated calcium channels;
    3. Csodium channels
19. 19TTX is a blocker of this type of channels:
    
    
    

    1. Aa) voltage-gated membrane sodium channels found in neurons;
    2. Bb) potassium membrane channels found in smooth muscle tissue with spontaneous bioelectric activity;
    3. Cc) non-activating sodium channels found in the cardiac sinoatrial node.
20. 20The passive trans-membrane transport of neutral molecules, when possible, is driven by:
    
    
    

    1. Aa) their electrochemical gradient;
    2. Bb) their electrical gradient;
    3. Cc) their concentration gradient.
21. 21Choose the correct statement regarding ligand-gated ion channels:
    
    
    

    1. Aa) they are inactivated by complementarity;
    2. Bb) they are activated by changes in the membrane potential;
    3. Cc) the ligand-receptor interaction leads to conformational changes in the protein structure.
22. 22 Conduction of inorganic ions through the plasma membrane is carried by:
    
    
    

    1. Aa) endocytosis;
    2. Bb) narrow water-filled channels with diameter of 0.3 – 0.65nm;
    3. Cc) phagocytosis.
23. 23Ion transport through the ion channels is:
    
    
    

    1. Aa) unidirectional;
    2. Bb) active;
    3. Cc) passive.
24. 24During the resting state of the cell, the Na+ electrochemical gradient points:
    
    
    

    1. Aa) from the extracellular into the intracellular space;
    2. Bb) from the intracellular into the extracellular space;
    3. Cc) in both directions.
25. 25The bonding of a specific channel blocker with a target ion channel will result in:
    
    

    1. Aa) inhibition of the passive transport of the particular ion species;
    2. Bb) inhibition of the active transport of the particular ion species;
    3. Cc) inhibition of the passive ion transport in the entire body.
26. 26The phospholipid bilayer of the plasma membrane allows passive diffusion of:
    
    
    

    1. Aa) small hydrophobic molecules: oxygen, nitrogen, and carbon dioxide;
    2. Bb) small inorganic ions: sodium, potassium, and magnesium;
    3. Cc) large organic molecules: amino acids, peptides, and glucose.
27. 27Which of the following names of ion channel structures is not part of the accepted terminology?
    
    
    

    1. Aa) narrow tunnel;
    2. Bb) opening;
    3. Cc) gating mechanism.
28. 28The default state of ion channels is:
    
    

    1. Aa) open;
    2. Bb) closed (deactivated);
    3. Cc) inactivated.
29. 29The type of transport through the ion channels is called:
    
    
    

    1. Aa) active;
    2. Bb) passive, driven by existing gradients;
    3. Cc) passive for some ions, and active for others.
30. 30What is the electric charge of the narrow tunnels in ion channels?
    
    
    

    1. Aa) positive;
    2. Bb) negative;
    3. Cc) opposite to the electric charge of the ion species that pass through the channel
31. 31In which of the following cases will a voltage-gated (potential-dependent) ion channel be activated?
    
    

    1. Aa) when the membrane potential is higher than the activation threshold for the ion channel
    2. Bb) when the membrane potential is at resting level
    3. Cc) when the membrane potential is lower than the activation threshold for the ion channel
32. 32Trans-membrane ion transport through ion channels is driven by:
    
    

    1. Aa) osmotic gradients;
    2. Bb) equilibrium potentials;
    3. Cc) electrochemical gradients.
33. 33Ion channels are (choose the best):
    
    
    

    1. Aa) integral proteins;
    2. Bb) transmembrane proteins;
    3. Cc) peripheral proteins.
34. 34An ion channel that could be activated by a hormone, neurotransmitter, mediator, or other
    biologically active substance is called:
    
    
    

    1. Aa) potential-dependent channels;
    2. Bb) ligand-gated channels;
    3. Cc) Ca2+ dependent channels.
35. 35Which of the following types of ion channels permit calcium, needed for the phasic contractions in
    smooth muscles, into the cell?
    

    1. Aa) ligand-gated channels;
    2. Bb) voltage-gated channels;
    3. Cc) stretch-gated channels (mechano-sensitive).

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Biophysics Quiz on Chapter 2, created by Y Y on 22/06/2019.

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