AAMC Bio Test Bank VERIFIED
CORRECT ANSWERS100%
The sodium pump would be most active in cells of which of the
following structures?
a. veins
b. loop of Henle
c. lungs
d. bone marrow - ---correct answers ---B: loop of Henle
- Na+ reabsorption is the most important function of loop of Henle
- Na+ reabsorbed from filtrate moving through nephron
- this is how kidneys concentrate urine
Nephron Structure - ---correct answers ---
How much is total body water of body weight? - ---correct answers
---- total body water is approximately 60% of body weight
How is total body water distributed? - ---correct answers ----
intracellular water: largest compartment; 40% of body weight
- extracellular water: 20% of water; divided into interstitial fluid (16%)
and blood plasma (4%)
,Where is sodium reabsorbed the most in the nephron? - ---correct
answers ---- proximal tubule: 70% sodium reabsorbed as sodium
bicarbonate and sodium chloride
- as sodium moves, water moves too: movement of water balances
osmotic pressure
What are reabsorbed in the early proximal tubule? - ---correct answers
---- glucose, lactate, citrate, amino acids "piggy back" on sodium co-
transporters
What are the transporters in the proximal tubule? - ---correct answers
---- Sodium/Potassium ATPase pump: three sodiums out for
reabsorption; two potassiums back inside
- Sodium/H+ Exchange Pump: allows reabsorption of bicarbonate,
proteins, amino acids
What are reabsorbed in the late proximal convoluted tubule? - ---
correct answers ---- high concentration of chloride due to the extensive
reabsorption of water in the early proximal tubule
- chloride reabsorbed back into blood
What is reabsorbed in the ascending loop of Henle? - ---correct
answers ---- 25% of Na+ and K+ are reabsorbed by sodium/potassium
ATPase pump
- impermeable to water so water isn't reabsorbed along with sodium
here
, What's reabsorbed in the distal tubule? - ---correct answers ----
reabsorbs 5% more of the sodium
- regulated mostly by hormones
It's postulated that the sodium pump directly causes action potentials
along neurons. Is this hypothesis reasonable?
a. No, action potentials result in an increased permeability of the plasma
membrane to sodium
b. No, myelin sheaths of neurons prevent the movement of ions across
the plasma membranes of neurons
c. Yes; sodium is transported out of the neurons during action potentials
d. Yes, action potentials are accompanied by the hydrolysis of ATP -
---correct answers ---A: the massive influx of sodium through voltage-
gated ion channels causes depolarization of the neuron that occurs
during the action potential
- some Na+ movement occurs down the length of the axon during the
action potential, but it doesn't depend on the sodium pump nor does it
cause action potentials
- sodium pump also function to move Na+ out of the cell , not into the
cell (not C)
- while sodium pump does use energy released by ATP hydrolysis, this
energy isn't used to cause the influx of sodium responsible for causing
action potentials (not D)
CORRECT ANSWERS100%
The sodium pump would be most active in cells of which of the
following structures?
a. veins
b. loop of Henle
c. lungs
d. bone marrow - ---correct answers ---B: loop of Henle
- Na+ reabsorption is the most important function of loop of Henle
- Na+ reabsorbed from filtrate moving through nephron
- this is how kidneys concentrate urine
Nephron Structure - ---correct answers ---
How much is total body water of body weight? - ---correct answers
---- total body water is approximately 60% of body weight
How is total body water distributed? - ---correct answers ----
intracellular water: largest compartment; 40% of body weight
- extracellular water: 20% of water; divided into interstitial fluid (16%)
and blood plasma (4%)
,Where is sodium reabsorbed the most in the nephron? - ---correct
answers ---- proximal tubule: 70% sodium reabsorbed as sodium
bicarbonate and sodium chloride
- as sodium moves, water moves too: movement of water balances
osmotic pressure
What are reabsorbed in the early proximal tubule? - ---correct answers
---- glucose, lactate, citrate, amino acids "piggy back" on sodium co-
transporters
What are the transporters in the proximal tubule? - ---correct answers
---- Sodium/Potassium ATPase pump: three sodiums out for
reabsorption; two potassiums back inside
- Sodium/H+ Exchange Pump: allows reabsorption of bicarbonate,
proteins, amino acids
What are reabsorbed in the late proximal convoluted tubule? - ---
correct answers ---- high concentration of chloride due to the extensive
reabsorption of water in the early proximal tubule
- chloride reabsorbed back into blood
What is reabsorbed in the ascending loop of Henle? - ---correct
answers ---- 25% of Na+ and K+ are reabsorbed by sodium/potassium
ATPase pump
- impermeable to water so water isn't reabsorbed along with sodium
here
, What's reabsorbed in the distal tubule? - ---correct answers ----
reabsorbs 5% more of the sodium
- regulated mostly by hormones
It's postulated that the sodium pump directly causes action potentials
along neurons. Is this hypothesis reasonable?
a. No, action potentials result in an increased permeability of the plasma
membrane to sodium
b. No, myelin sheaths of neurons prevent the movement of ions across
the plasma membranes of neurons
c. Yes; sodium is transported out of the neurons during action potentials
d. Yes, action potentials are accompanied by the hydrolysis of ATP -
---correct answers ---A: the massive influx of sodium through voltage-
gated ion channels causes depolarization of the neuron that occurs
during the action potential
- some Na+ movement occurs down the length of the axon during the
action potential, but it doesn't depend on the sodium pump nor does it
cause action potentials
- sodium pump also function to move Na+ out of the cell , not into the
cell (not C)
- while sodium pump does use energy released by ATP hydrolysis, this
energy isn't used to cause the influx of sodium responsible for causing
action potentials (not D)
