Questions and actual answers
Chapter 1: Cellular Biology
MULTIPLE CHOICE
The exact mechanism for the transport of Na+ and K+ across the membrane is uncertain. One
proposal is that ATPase enzyme induces the transporter protein to undergo several
conformational changes, causing Na+ and K+ to move short distances (see Figure 1-29). The
remaining options do not correctly describe the means by which K+ and Na+ are transported.
PTS: 1 REF: Pages 32-33
27. What occurs during exocytosis?
a.
Macromolecules can be secreted across eukaryotic cell membranes.
b.
All substances are secreted into the cellular matrix.
c.
No repairs in the plasma membrane can take place.
d.
Solute molecules flow freely into and out of the cell. ✔️✔️ANS: A
,In eukaryotic cells, secretion of macromolecules almost always occurs by exocytosis. The
remaining options do not correctly describe exocytosis.
PTS: 1 REF: Pages 35-36
28. Why is it possible for potassium to diffuse easily into and out of cells?
a.
Potassium has a greater concentration in the intracellular fluid (ICF).
b.
Sodium has a greater concentration in the extracellular fluid (ECF).
c.
The resting plasma membrane is more permeable to potassium.
d.
An excess of anions are inside the cell. ✔️✔️ANS: C
Because the resting plasma membrane is more permeable to K+ than to Na+, K+ can easily
diffuse from its area of higher concentration in the ICF to its area of lower concentration in the
ECF. Because Na+ and K+ are both cations, the net result is an excess of anions inside the cell,
resulting in the resting membrane potential. The remaining options do not correctly identify the
process that most easily diffuses K+.
PTS: 1 REF: Page 36
29. The cellular uptake of the nutrient cholesterol depends on which process?
,a.
Receptor-mediated exocytosis
b.
Antiport system
c.
Receptor-mediated endocytosis
d.
Passive transport ✔️✔️ANS: C
The cellular uptake of nutrients, such as cholesterol, for example, depends on receptor-mediated
endocytosis. Nutrients are not transported via the other options.
30. What causes the rapid change in the resting membrane potential to initiate an action
potential?
a.
Potassium gates open, and potassium rushes into the cell, changing the membrane potential from
negative to positive.
b.
Sodium gates open, and sodium rushes into the cell, changing the membrane potential from
negative to positive.
c.
, Sodium gates close, allowing potassium into the cell to change the membrane potential from
positive to negative.
d.
Potassium gates close, allowing sodium into the cell to change the membrane potential from
positive to negative. ✔️✔️ANS: B
When a resting cell is stimulated through voltage-regulated channels, the cell membranes
become more permeable to Na+. A net Na+ moves into the cell, and the membrane potential
decreases, or moves forward, from a negative value (in millivolts) to zero. The Na+ gates open,
and Na+ rushes into the cell, causing the membrane potential to reduce to zero and then become
positive (depolarization). The remaining options do not correctly describe the change that
initiates an action potential.
PTS: 1 REF: Page 36
32. The role of cytokines in cell reproduction is that they:
a.
Provide growth factor for tissue growth and development.
b.
Block progress of cell reproduction through the cell cycle.
c.
Restrain cell growth and development.
d.
Provide nutrients for cell growth and development. ✔️✔️ANS: A
Chapter 1: Cellular Biology
MULTIPLE CHOICE
The exact mechanism for the transport of Na+ and K+ across the membrane is uncertain. One
proposal is that ATPase enzyme induces the transporter protein to undergo several
conformational changes, causing Na+ and K+ to move short distances (see Figure 1-29). The
remaining options do not correctly describe the means by which K+ and Na+ are transported.
PTS: 1 REF: Pages 32-33
27. What occurs during exocytosis?
a.
Macromolecules can be secreted across eukaryotic cell membranes.
b.
All substances are secreted into the cellular matrix.
c.
No repairs in the plasma membrane can take place.
d.
Solute molecules flow freely into and out of the cell. ✔️✔️ANS: A
,In eukaryotic cells, secretion of macromolecules almost always occurs by exocytosis. The
remaining options do not correctly describe exocytosis.
PTS: 1 REF: Pages 35-36
28. Why is it possible for potassium to diffuse easily into and out of cells?
a.
Potassium has a greater concentration in the intracellular fluid (ICF).
b.
Sodium has a greater concentration in the extracellular fluid (ECF).
c.
The resting plasma membrane is more permeable to potassium.
d.
An excess of anions are inside the cell. ✔️✔️ANS: C
Because the resting plasma membrane is more permeable to K+ than to Na+, K+ can easily
diffuse from its area of higher concentration in the ICF to its area of lower concentration in the
ECF. Because Na+ and K+ are both cations, the net result is an excess of anions inside the cell,
resulting in the resting membrane potential. The remaining options do not correctly identify the
process that most easily diffuses K+.
PTS: 1 REF: Page 36
29. The cellular uptake of the nutrient cholesterol depends on which process?
,a.
Receptor-mediated exocytosis
b.
Antiport system
c.
Receptor-mediated endocytosis
d.
Passive transport ✔️✔️ANS: C
The cellular uptake of nutrients, such as cholesterol, for example, depends on receptor-mediated
endocytosis. Nutrients are not transported via the other options.
30. What causes the rapid change in the resting membrane potential to initiate an action
potential?
a.
Potassium gates open, and potassium rushes into the cell, changing the membrane potential from
negative to positive.
b.
Sodium gates open, and sodium rushes into the cell, changing the membrane potential from
negative to positive.
c.
, Sodium gates close, allowing potassium into the cell to change the membrane potential from
positive to negative.
d.
Potassium gates close, allowing sodium into the cell to change the membrane potential from
positive to negative. ✔️✔️ANS: B
When a resting cell is stimulated through voltage-regulated channels, the cell membranes
become more permeable to Na+. A net Na+ moves into the cell, and the membrane potential
decreases, or moves forward, from a negative value (in millivolts) to zero. The Na+ gates open,
and Na+ rushes into the cell, causing the membrane potential to reduce to zero and then become
positive (depolarization). The remaining options do not correctly describe the change that
initiates an action potential.
PTS: 1 REF: Page 36
32. The role of cytokines in cell reproduction is that they:
a.
Provide growth factor for tissue growth and development.
b.
Block progress of cell reproduction through the cell cycle.
c.
Restrain cell growth and development.
d.
Provide nutrients for cell growth and development. ✔️✔️ANS: A
