Biol1000 Fall 2013 – Test 2
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Page 1 of 11 Biol1000 Fall 2013 – Test 2
1. How does the fluid mosaic model fit our understanding of membrane
A. Fluid mosaic refers to the different types of lipid within the membrane and the
tendency for the membrane to melt given a high enough temperature.
B. The fluid refers to the ability of lipid to move freely within a flexible membrane
and mosaic refers the presence of a variety of different types of protein and other
components within the membrane.
C. The fluid refers to the presence of water surrounding the membrane and mosaic
refers to the presence of both saturated and unsaturated fats.
D. The fluid refers to the ability of ions and other molecules to flow across the
membrane and mosaic refers to the diversity of molecules that can cross.
2. Which of the following statements about membrane structure is true?
A. Cholesterol molecules extend across the lipid bilayer, so that their charged ends
can interact with water.
B. Glycolipids are only found on the cytoplasmic side.
C. Lipids move readily within one side of the bilayer, but rarely flip from one side to
D. Peripheral proteins are usually found only on the cell surface, not the cytoplasmic
side of the membrane.
3. You are a scientist and are studying the plasma membrane of bacteria. You
leave the bacteria growing in a water bath overnight at 23 C but the electricity
goes out after you leave and the temperature drops to 15 C . When you get back
several hours later, what will you expect to see when you analyze the bacterial
A. The loss of sterols from the membrane.
B. Lower levels of saturated fats.
C. Higher levels of saturated fats.
D. Higher levels of trans fats.
4. Which of the following molecules is likely to move most quickly across the
membrane by simple diffusion and why?
A. O -ecause it is non polar
B. Cl because it is negatively charged.
C. Na because it is small.
D. Glucose because it is polar
E. There would be no difference in the rate of diffusion across the membrane for
Page 2 of 11 Biol1000 Fall 2013 – Test 2
5. Side A of a membrane contains 0.05 µM of sodium. Side B of this membrane
contains 0.05 µM of sodium. Diffusion of sodium across the membrane occurs
via an open channel. Based on this information predict the direction of movement
A. Sodium will move from Side A to Side B
B. Sodium will move from Side B to Side A
C. There will be no movement of sodium across the membrane.
D. Sodium will move in both directions at equal rates.
6. You are working with two artificial membranes in the lab. They are both
identical in terms of lipid content except that lipid A has three times more
cholesterol content than lipid B. As you increase the temperature, which of the
two will melt first?
A. Lipid A will melt first as the cholesterol will tend to prevent the fatty acid tails from
aligning and packing tightly.
B. Lipid A will melt first as the cholesterol will align with the unsaturated fats but not
the saturated fats.
C. Lipid A will melt last as the cholesterol will interact with the fatty acid tails and
restrict phospholipid movement.
D. Lipid A and Lipid B will melt at about the same temperature as cholesterol
content does not affect membrane fluidity.
7. A cell is placed in a solution of growth medium that has a solute concentration
of 3.0 mM. The internal solute concentration of the cell is 0.2 mM. Which of the
following statements is true?
A. The growth medium is hypertonic compared to the cytoplasm and the cell will
B. The growth medium is hypotonic compared to the cytoplasm and the cell will
C. The growth medium is isotonic compared to the cytoplasm and the cell will
D. The growth medium is hypertonic compared to the cytoplasm and the cell will
E. None of the above.
8. Which of the following includes all others presented below?
B. Passive Transport
C. Facilitated Diffusion
D. Movement of a solute through a channel protein.
Page 3 of 11 Biol1000 Fall 2013 – Test 2
9. Through the process of endocytosis, some cells internalize (engulf) about
100% of their plasma membrane in approximately 30 minutes. The cell surface to
volume ratio of these cells never change. How is this possible?
A. The plasma membrane is not included in cell surface to volume
B. Exocytosis replaces the internalized plasma membrane at a rate equal to
C. Phospholipids are removed from the plasma membrane to maintain
surface area to volume ratios.
D. Expansion of the endomembrane area, due to fusing of endocytotic
vesicles, makes up for the reduction in plasma membrane surface area.
10. Lactose is moved into E. coli using a H /lactos+ symporter. Based on your
knowledge of symporters, what is the role of H ?
A. It is moving into the cell against its concentration gradient.
B. It is binding to the transport protein to open the gated lactose channel.
C. It is moving out of the cell against its concentration gradient.
D. It is moving into the cell along its concentration gradient.
E. It is binding to lactose and changing its conformation. The lactose/H +
complex then binds the receptor site on the transport protein.
11. In question #10 above, what type of transport is this?
A. primary active transport
B. secondary active transport
C. facilitated diffusion
D. transport via a gated ion channel
12. Some viruses inject their DNA into cells, but others are taken in whole by
cells. How are they likely to be transported into the cell?
C. active transport
Page 4 of 11 Biol1000 Fall 2013 – Test 2
13. You are studying the movement of solute X across a cell membrane and want
to know how it is moving across. You run an experiment measuring the rate of
movement (called diffusion rate in the graph) at different concentration gradients
of solute X across the membrane. You obtain the following curve:
What is the best conclusion given these data?
A. The solute is crossing by simple diffusion.
B. The solute is crossing by facilitated diffusion.
C. The solute could be crossing by simple or facilitated diffusion.
D. The solute must be using active transport.
14. Is the follo