Advanced Science: Diffusion And Osmosis Quiz (2nd Trimester, 2014-2015)
- 1.
Water is a molecule that needs small pores (embedded in the membrane of a cell) to move by diffusion into a cell. What are these small pores called?
- A.
Aquaporins
- B.
Apertures
- C.
Orofices
- D.
Water channels
Correct Answer
A. AquaporinsExplanation
Aquaporins are membrane water channels that regulate the passage of water through cell membranes.Rate this question:
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- 2.
Once molecules reach a dynamic equilibrium on either side of a membrane they stop moving.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
This is false. With the exception of the theoretical "absolute zero" molecules are ALWAYS in motion.Rate this question:
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- 3.
Diffusion is the net movement of molecules from an area of ______________________ concentration to an area of ___________________ concentration.* (Place a comma to separate your two answers).
Correct Answer
higher, lower
high, low
high, lower
higher concentration, lower
higher concentration, lower concentration
high concentration, low
higher concentration, low
higher concentration, low concentration
high concentration, low concentration
higher, low
high,low higher,lowerExplanation
Diffusion is the net movement of molecules from an area of higher concentration to an area of lower concentration. This process occurs due to the random motion of molecules and aims to equalize the concentration of molecules throughout the given space. The concentration gradient, which is the difference in concentration between two areas, drives the movement of molecules from an area of higher concentration to an area of lower concentration. This movement continues until equilibrium is reached, where the concentration becomes equal throughout the space.Rate this question:
- 4.
The thing that drives the diffusion of molecules are molecular collisions.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Yep! Molecular collisions impart force (kinetic energy) from one molecule to another, and this ultimately leads to molecules spreading from one area to another. We've also learned that when there are more molecules in an area, they have a greater chance of colliding and imparting their force, thus molecules tend to move from areas of high to lower concentrations.Rate this question:
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- 5.
The brownish/orange circle is a cell and the white ring represents its membrane. In which picture (A, B, or C) shows a hypertonic solution inside the cell, compared to a hypotonic solution outside the cell? (Note: the green "dots" represent salt molecules).
Correct Answer
A
aExplanation
"A" shows more salt inside the cell (hypertonic) and less salt outside of the cell (hypotonic); there is more salt inside the cell compared to the outside of the cell.Rate this question:
- 6.
The brownish/orange circle is a cell and the white ring represents its membrane. In which picture (A, B, or C) shows a isotonic solution inside and outside of the cell? (Note: the green "dots" represent salt molecules).
Correct Answer
B
bExplanation
In picture B, the green dots representing salt molecules are evenly distributed both inside and outside the cell. This indicates that the concentration of salt is the same inside and outside the cell, suggesting an isotonic solution.Rate this question:
- 7.
You eat spaghetti for dinner and digest the starch in it to glucose. The glucose is now in high concentration in the cells of your small intestine, relative to its concentration in your bloodstream. Predictably, the glucose diffuses across the cell membrane of the cells lining your small intestine and into the bloodstream.
- A.
True, because diffusion moves molecules from a high to low concentration.
- B.
False, because molecules cannot move across membranes by diffusion.
- C.
False, because diffusion moves molecules from a low to high concentration.
- D.
False, because molecules such as sugar are too large to move across cell membranes.
- E.
False, because energy is required for diffusion.
Correct Answer
A. True, because diffusion moves molecules from a high to low concentration.Explanation
This answer is true; molecules move from areas of high to low concentration. This movement is called diffusion and is a type of passive transport (it doesn't require extra cellular energy).Rate this question:
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- 8.
Molecules are often said to: "move in constant random motion". Why do molecules appear to move that way? Choose the best answer.
- A.
Because molecules have kinetic energy.
- B.
Because molecules have potential energy.
- C.
Because molecules are constantly colliding with each other.
- D.
Because they move randomly due to the laws of physics.
Correct Answer
C. Because molecules are constantly colliding with each other.Explanation
Molecules appear to move randomly, however in reality their movement is directly related to collisions with other molecules that are happening all the time. When molecules "collide" they impart their force (kinetic energy) onto each other.Rate this question:
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- 9.
What are "free" water molecules?
- A.
Water molecules that don't require energy to move across cell membranes.
- B.
Water molecules that are not bound to solutes (such as salt).
- C.
Water molecules that are bound to salt molecules.
- D.
Water molecules that are not connected to each other.
Correct Answer
B. Water molecules that are not bound to solutes (such as salt).Explanation
"Free" water molecules are water molecules that are not bound to solutes (such as salt).Rate this question:
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- 10.
Molecular motion stops when:
- A.
Collisions stop occurring.
- B.
When two solutions become isotonic.
- C.
All of the molecules have moved from high to low concentration.
- D.
Molecules never stop moving. (Unless they reach absolute zero, and even this state is open to debate).
Correct Answer
D. Molecules never stop moving. (Unless they reach absolute zero, and even this state is open to debate).Explanation
Molecules never stop moving. Even at absolute zero molecular motion is governed by the laws of quantum physics, thus many believe that molecules (and their atoms) would still vibrate at absolute zero.Rate this question:
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- 11.
What term means the concentrations of a molecule are equal on both sides of a membrane?
- A.
A.) Hypertonic
- B.
B.) Hypotonic
- C.
C.) Isotonic
- D.
D.) Dynamic equilibrium
- E.
Both "C" and "D' are correct
Correct Answer
E. Both "C" and "D' are correctExplanation
Both the terms "Isotonic" and "Dynamic Equilibrium" describe conditions where the concentrations of a molecule are equal on both sides of a membrane.Rate this question:
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- 12.
A molecule can move from low to high concentration.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Yep. Molecules just move based on their own kinetic energy and change direction based on collisions. Molecules can move from an area of lower to higher concentrations, but this occurs less frequently then molecules moving from high to low. This occurs because when the density of molecules are higher in a region they have a greater likelihood to collide with each other. These collisions ultimately cause more denser areas of molecules to spread out and move from high concentration to a lower concentration.Rate this question:
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- 13.
Water molecules have a net movement from an area of lower solute concentration to an area of high solute concentration.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
True! This may sound incorrect, but solute refers to a substance (like salt) dissolved by a solvent (such as water). Thus an area of low solute would have a high concentration of solvent (or water), and this water would have a net movement from an area of higher to lower concentration.Rate this question:
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- 14.
What term describes a membrane that allows some substances to pass through and prevents other substances from passing across it.
- A.
Selectively permeable
- B.
Permeable
- C.
Impermeable
- D.
Special barrier
Correct Answer
A. Selectively permeableExplanation
Membranes that only allow certain substances to pass across are called selectively (or sometimes semi-) permeable.Rate this question:
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- 15.
Slugs die when salted. Pick the best explanation for this action:
- A.
Salt damages the slug's cells.
- B.
A higher solute (salt) concentration on the outside of the slug creates a concentration gradient where water moves out of the slug rapidly, causing the slug's cells to rapidly dehydrate.
- C.
A higher solvent (water) concentration on the outside of the slug causes a concentration gradient when water moves into the slug rapidly, causing the slug's cells to burst.
- D.
Salt enters the slug's cells and pushes water out of the slug, causing it to dehydrate.
Correct Answer
B. A higher solute (salt) concentration on the outside of the slug creates a concentration gradient where water moves out of the slug rapidly, causing the slug's cells to rapidly dehydrate.Explanation
The higher salt concentration outside the slug create a concentration gradient where water moves by osmosis, rapidly out the slug's cells.Rate this question:
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- 16.
Which answer best explains why the Gummy Bears from our lab were larger the next day, after being placed in distilled water?
- A.
Salt entered by osmosis from an area of high to lower concentration.
- B.
Gummy bears often eat sugar during the day and grow overnight.
- C.
A concentration gradient moved water from an area of low to higher concentration.
- D.
Water entered the bears by osmosis from an area of high to lower concentration.
Correct Answer
D. Water entered the bears by osmosis from an area of high to lower concentration.Explanation
Distilled water is water with salts removed. When the bear was placed in distilled water, there was a high concentration of water on the outside of the bear and a (much) lower concentration of water on the inside of the bear. This created a large concentration gradient and water moved (by osmosis) into the bear from an area of high to lower concentration.Rate this question:
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- 17.
Osmosis is a type of diffusion.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Yep. Osmosis is the diffusion of water.Rate this question:
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- 18.
After completing the "Gummy Bear Lab", a student noticed that their bear had changed color from a dark green to almost colorless. Which answer best explains this observation?
- A.
Water breaks down the green dye/pigment used to color the bear.
- B.
The green dye/pigment diffused from an area of high to an area of lower concentration.
- C.
As water moved into the bear, it pushed the green dye/pigment out.
- D.
Green gummy bears possess chlorophyll for photosynthesis... this chlorophyll breaks down rapidly in the presence of water.
Correct Answer
B. The green dye/pigment diffused from an area of high to an area of lower concentration.Explanation
Most likely the green dye/pigment diffused from an area of high concentration (inside the bear) to an area of lower concentration (outside the bear into the water).Rate this question:
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- 19.
Diffusion stops if there is no concentration gradient.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Yep. There is only a net movement from one area, to another, if there is a concentration gradient (a difference in the concentration of a molecule between one area and another. This difference leads to more molecules in one region (greater density of molecules) colliding more frequently, and thus spreading out more from an area.Rate this question:
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- 20.
If an animal cell was placed in a hypertonic solution, which answer best predicts what would happen?
- A.
The cell will shrivel and possibly die due to loss of water by osmosis.
- B.
The cell will expand and possibly die due to the gain of water by osmosis.
- C.
The cell will shrivel and possibly die due to loss of salt by diffusion.
- D.
The cell will expand and possibly die due to the gain of salt by diffusion.
Correct Answer
A. The cell will shrivel and possibly die due to loss of water by osmosis.Explanation
The cell was placed in a hypertonic solution. This means it was placed in a solution that had a high solute (salt) concentration. Thus the cell had a higher concentration of free water molecules inside the cell and water moved from an area of high free water concentration to an area of lower concentration (outside the cell). This resulted in the cell losing water by osmosis and shriveling.Rate this question:
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.png "The brownish/orange circle is a cell and the white ring represents its membrane. In which picture (A, B, or C) shows a hypertonic solution inside the cell, compared to a hypotonic solution outside the cell? (Note: the green \"dots\" represent salt molecules).")
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