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When a molecule moves across the plasma membrane by active transport,
a. it always moves against the concentration gradient
b. its energy grows
c. it moves in opposite direction than water
d. its movement depends on its metabolic change
All active transport theories assumebinding of the transported molecule to an element of plasma membrane:
a. the presence of a transporter molecule
b. the influence of a humoral control
c. the influence of a cortical control
d. presence of uni-directional channels
What is not a property of neuronal plasma membrane?
a. Permeability for K+
b. It is very little permeable for Na+ in the resting state.
c. The maintaining of a concentration gradient of ions across the plasma membrane is independent of energy metabolism.
d. Its excitability is different in different parts of a neurone.
e. It doesn't have a refractory period.
The change of relative permeability of plasma membrane for sodium causes the change of all the following phenomena except:
a. resting potential
b. cell volume
c. intracellular concentration of Na+
e. resting equilibrium potential
Most cells in the human body in equilibrium maintain high intracellular concentration of K+ and low intracellular concentration of Na+. Which phenomenon is responsible for this ion asymmetry the most?
a. The plasma membrane is more permeable for K+ than for Na+ at rest.
b. The threshold membrane potential maintains the ion difference.
c. The difference is caused by the intracellular osmotic pressure.
d. The difference is caused by the activity of the sodium-potassium pump and resting membrane permeability.
e. Na+ and K+ are of different sizes after hydration.
Diffusion is best described as a(n)
a. passive process down the concentration gradient:
b. active process iagainst the concentration gradient
c. process driven by pressure, such as blood pressure and surface tension
d. active process concerning only substances with low molecular weight
e. active or passive process whose speed is exclusively determined by the surface of the membrane on which the diffusion is going on
Which of these items can be described as "all-or-none"?
a. force of muscle contration
b. resting potential
c. action potential amount or neurotransmitter released
d. EPSP (excitatory postsynaptic potential)
Excitable cells (neurones and myocytes) differ from other cells by:
a. having an electrical membrane
b. having an ion concentration gradient across the plasma membrane
c. being able to generate fast and transient changes for sodium permeability
b. having active transport mechanisms on their membranes
e. the fact that their membrane is affected by electric current
This is true for the so-called sodium-potassium pump:
a. speed of sodium transport is independent of its intracellular concentration
b. macroergic phosphates allow the activity of the sodium-potassium pump
c. activity of the Na+-K+-pump is independent of K+ influx
d. its function does not depend on temperatureit is a mechanism of sodium diffusion
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