BELL RINGER
TEST YOUR FOUNDATIONAL KNOWLDEGE!!!! READ.TAKE A BREATH. IDENTIFY
KEY TERMS/PHRASES. REREAD.
Rhodopsins are light-sensitive molecules composed of a protein (opsin) and retinal (derivative of
vitamin A). Opsin is a membrane protein with several -helical segments that loop back and forth
through the plasma membrane. There are two classes of rhodopsins. According to Oded Beje,
one class has relatively slow dynamics (a photocycle of approximately 0.5 second) and is well
suited for light detection. The second class has faster dynamics (a photocycle of approximately
cell membranes. Oded Beje was the first, in September 2000, to report on a rhodopsin
(proteorhodopsin) found in the domain Bacteria. [Source: O. Beje et al., Science 289 (2000):
1902.]
1) Which of the following best describes this particular protein?
A) integral
B) peripheral
C) external
D) internal
2) Proteorhodopsin consists of a single polypeptide chain. What is the highest level of structure
found in this protein?
A) primary
B) secondary
C) tertiary
D) quaternary
3) Sodium-potassium pumps:
A) move three potassium ions and two sodium ions while producing an ATP for each cycle.
B) move two potassium ions and three sodium ions while consuming an ATP for each cycle.
C) produce ATP for cells while making the outside of cell membranes negatively charged.
D) use ATP molecules to move protons to the inner side of cell membranes.
CELL MEMBRANE & CELL TRANSPORT QUIZ
Print it out OR copy the question and answer
1) Phospholipids can form all of the following structures in water except which one?
A) micelles
B) bilayers
C) monolayers
D) vesicles
2) Phospholipid bilayer membranes are selectively permeable; in which way are they "selectively
permeable"?
A) They allow everything but water to cross.
B) They allow only water to cross.
C) They allow everything nonpolar to cross.
D) They allow some things to cross while restricting others.
3) Which of the following substances would most likely require a protein to facilitate its
diffusion across a cell membrane?
A) water
B) glycerol
C) fatty acid
D) oxygen gas (O2)
4) If you mechanically shook a mixture of amphipathic lipids and water, what would you expect
to see when the solution is observed with an electron microscope?
A) The lipids and water will have separated into two distinct layers because the lipids are
partially nonpolar.
B) The lipids will have formed tiny vesicles filled with water.
C) The lipids will have formed planar bilayer membranes.
D) The lipids will have completely dissolved in solution because they are partially polar.
5) What do phospholipids and triglycerides have in common?
A) They both contain serine or some other organic compound.
B) They both have three fatty acids.
C) They both have a glycerol backbone.
D) They both have a phosphate.
6) In an experiment involving planar bilayers, a solution of table salt (sodium and chloride ions
in water) is added on the left side of the membrane while pure water is added on the right side.
After 30 minutes the researchers test for the presence of ions on each side of the membrane. The
right side tests negative for ions. What can you conclude?
A) The experiment failed.
B) The water somehow blocked the movement of ions across the membrane.
C) The left side would probably also test negative for ions.
D) Ions cannot cross planar bilayers.
7) Which of the following is the best explanation for why vegetable oil is a liquid at room
temperature while animal fats are solid?
A) Vegetable oil has more double bonds than animal fats.
B) Vegetable oil has fewer double bonds than animal fats.
C) Animal fats have no amphipathic character.
D) Vegetable oil has longer fatty-acid tails than animal fats have.
8) Which of the following crosses lipid bilayers the fastest?
A) a sodium ion
B) a small, polar molecule like water
C) a large, polar molecule like glucose
D) a small, nonpolar molecule like oxygen (O2)
9) Why does cholesterol lower membrane permeability?
A) It is polar.
B) It fills gaps in membranes and increases hydrophobic interactions.
C) It participates in hydrogen bonding in the membrane interior.
D) It is small relative to most phospholipids.
10) What will happen to a red blood cell (rbc), which has an internal ion concentration of about
0.9 percent, if it is placed into a beaker of pure water?
A) Nothing.
B) The cell would shrink because the water in the beaker is hypotonic relative to the cytoplasm
of the rbc.
C) The cell would shrink because the water in the beaker is hypertonic hypotonic relative to the
cytoplasm of the rbc.
D) The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of
the rbc.
11) Under what circumstances does membrane transport always require energy?
A) whenever molecules are moved that are too large to pass through the phospholipid bilayer
membrane
B) whenever a solute needs to be moved from low concentration to high concentration through a
phospholipid bilayer membrane
C) whenever a solute is charged, such as an ion, and is moved through a phospholipid bilayer
membrane
D) whenever a molecule is polar and is moved through a phospholipid bilayer membrane
12) What is the most important factor in explaining why diffusion occurs spontaneously?
A) It leads to an increase in entropy.
B) It leads to a decrease in entropy.
C) The process is exothermic.
D) The process is endothermic.
13) What is the most important factor in explaining why osmosis occurs spontaneously?
A) It leads to an increase in entropy.
B) It leads to a decrease in entropy.
C) The process is exothermic.
D) The process is endothermic.
14) Which of the following is not true of osmosis?
A) It is a special case of diffusion.
B) It is an energy-demanding or "active" process.
C) Water moves from areas of high water concentration to areas of low water concentration.
15) Suppose some blood cells were in an isotonic solution. What would happen to them?
A) They would shrink.
B) They would expand.
C) They would remain the same size.
D) The outcome is not predictable.
16) What is the name of the currently accepted model of membrane structure, and where does it
place membrane proteins?
A) fluid-mosaic; on the surfaces of the membrane only
B) fluid-mosaic; embedded within the membrane and on the surfaces of the membrane
C) sandwich; on the outside and inside surfaces of the membrane only
D) sandwich; embedded within the membrane and on the surfaces of the membrane
17) Where would you most likely find an integral membrane protein?
A) on the inside surface of the cell membrane
B) on the outside surface of the cell membrane
C) floating freely in the cytoplasm
D) spanning the cell membrane, with parts of the protein visible from both the inside and the
outside of the cell
18) Which of the following means of transport would most likely be used for moving a mediumsized molecule (like a monosaccharide or an amino acid) from a low concentration on the outside
of a cell to a high concentration on the inside of a cell?
A) facilitated diffusion through an ion channel protein
B) facilitated diffusion through a transporter protein
C) active transport through a "pump" protein
D) passive transport