BIO 189 Midterm
1. Which of the following best describes the structure of a biological membrane
A. two layers of phospholipids (with opposite orientations of the phospholipids in each
layer) with each layer covered on the outside with proteins
B. a fluid structure in which phospholipids and proteins move freely between sides of the
membrane
C. a mixture of covalently linked phospholipids and proteins that determines which solutes
can cross the membrane and which cannot
D. two layers of phospholipids with proteins embedded between the two lay-ers
E. two layers of phospholipids with proteins either crossing the layers or on the
surface of the layers: E. two layers of phospholipids with proteins either crossing the layers
or on the surface of the layers
2. Which of the following is a reasonable explanation for why unsaturated fatty
acids help keep any membrane more fluid at lower temperature?
A. The double bonds form kinks in the fatty acid tail, forcing adjacent lipids to be further
apart.
B. Unsaturated fatty acids have a higher cholesterol content and therefore more
cholesterol in their membranes.
C. Unsaturated fatty acids are more polar than saturated fatty acids.
D. The double bonds block interaction among the hydrophilic head groups of the lipids.
E. The double bonds result in shorter fatty acid tails and thinner membranes.: A.
The double bonds form kinks in the fatty acid tail, forcing adjacent lipids to be further apart.
3. Which component is the fiber of the extracellular matrix?
(Google image; black & white): A
4. Celery stalks that are immersed in fresh water for several hours become
stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and
soft. From this we can deduce that
,BIO 189 Midterm
A. The fresh water is hypotonic & the salt solution is hypertonic to the cells of the celery
stalks
B. the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery
stalks.
C. the fresh water and the salt solution are both hypotonic to the cells of the celery stalks.
D. the fresh water is isotonic and the salt solution is hypertonic to the cells of the celery
stalks.
E. the fresh water and the salt solution are both hypertonic to the cells of the
celery stalks.: A. The fresh water is hypotonic & the salt solution is hypertonic to the cells
of the celery stalks
5. Which of the following statements about osmosis is correct?
A. Osmotic movement of water into a cell would likely occur if the cell accumu-lates water
from its environment
B. Osmosis is the diffusion of water from a region of lower water concentration to a region
of higher water concentration
C. The presence of aquaporins (proteins that form water channels in the mem-brane)
should speed up the process of osmosis.
D. If a cell is placed in an isotonic solution, more water will enter the cell than leaves the
cell.
E. If a solution outside the cell is hypertonic compared to the cytoplasm, water
will move into the cell by osmosis: C. The presence of aquaporins (proteins that form water
channels in the membrane) should speed up the process of osmosis.
(Aquaporins facilitate water movement across membranes and thus speed up the process
of osmosis.)
6. The solutions in the arms of a U-tube are separated at the bottom of the tube
by a selectively permeable membrane. The membrane is permeable to sodium
chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and
1. Which of the following best describes the structure of a biological membrane
A. two layers of phospholipids (with opposite orientations of the phospholipids in each
layer) with each layer covered on the outside with proteins
B. a fluid structure in which phospholipids and proteins move freely between sides of the
membrane
C. a mixture of covalently linked phospholipids and proteins that determines which solutes
can cross the membrane and which cannot
D. two layers of phospholipids with proteins embedded between the two lay-ers
E. two layers of phospholipids with proteins either crossing the layers or on the
surface of the layers: E. two layers of phospholipids with proteins either crossing the layers
or on the surface of the layers
2. Which of the following is a reasonable explanation for why unsaturated fatty
acids help keep any membrane more fluid at lower temperature?
A. The double bonds form kinks in the fatty acid tail, forcing adjacent lipids to be further
apart.
B. Unsaturated fatty acids have a higher cholesterol content and therefore more
cholesterol in their membranes.
C. Unsaturated fatty acids are more polar than saturated fatty acids.
D. The double bonds block interaction among the hydrophilic head groups of the lipids.
E. The double bonds result in shorter fatty acid tails and thinner membranes.: A.
The double bonds form kinks in the fatty acid tail, forcing adjacent lipids to be further apart.
3. Which component is the fiber of the extracellular matrix?
(Google image; black & white): A
4. Celery stalks that are immersed in fresh water for several hours become
stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and
soft. From this we can deduce that
,BIO 189 Midterm
A. The fresh water is hypotonic & the salt solution is hypertonic to the cells of the celery
stalks
B. the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery
stalks.
C. the fresh water and the salt solution are both hypotonic to the cells of the celery stalks.
D. the fresh water is isotonic and the salt solution is hypertonic to the cells of the celery
stalks.
E. the fresh water and the salt solution are both hypertonic to the cells of the
celery stalks.: A. The fresh water is hypotonic & the salt solution is hypertonic to the cells
of the celery stalks
5. Which of the following statements about osmosis is correct?
A. Osmotic movement of water into a cell would likely occur if the cell accumu-lates water
from its environment
B. Osmosis is the diffusion of water from a region of lower water concentration to a region
of higher water concentration
C. The presence of aquaporins (proteins that form water channels in the mem-brane)
should speed up the process of osmosis.
D. If a cell is placed in an isotonic solution, more water will enter the cell than leaves the
cell.
E. If a solution outside the cell is hypertonic compared to the cytoplasm, water
will move into the cell by osmosis: C. The presence of aquaporins (proteins that form water
channels in the membrane) should speed up the process of osmosis.
(Aquaporins facilitate water movement across membranes and thus speed up the process
of osmosis.)
6. The solutions in the arms of a U-tube are separated at the bottom of the tube
by a selectively permeable membrane. The membrane is permeable to sodium
chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and
