Advanced Science: Diffusion and Osmosis Quiz (2nd Trimester, 2014-2015)

1.

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).

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.

Explanation

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.

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2. Osmosis is a type of diffusion.

True

False

Yep. Osmosis is the diffusion of water.

Explanation

Yep. Osmosis is the diffusion of water.

3. What term describes a membrane that allows some substances to pass through and prevents other substances from passing across it.

Selectively permeable

Permeable

Impermeable

Special barrier

Membranes that only allow certain substances to pass across are called selectively (or sometimes semi-) permeable.

Explanation

Membranes that only allow certain substances to pass across are called selectively (or sometimes semi-) permeable.

4. Slugs die when salted. Pick the best explanation for this action:

Salt damages the slug's cells.

Salt enters the slug's cells and pushes water out of the slug, causing it to dehydrate.

The higher salt concentration outside the slug create a concentration gradient where water moves by osmosis, rapidly out the slug's cells.

Explanation

The higher salt concentration outside the slug create a concentration gradient where water moves by osmosis, rapidly out the slug's cells.

5. 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).

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.

Explanation

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.

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6.

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).

"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.

Explanation

"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.

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7. A molecule can move from low to high concentration.

True

False

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.

Explanation

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.

8. Molecular motion stops when:

Collisions stop occurring.

When two solutions become isotonic.

All of the molecules have moved from high to low concentration.

Molecules never stop moving. (Unless they reach absolute zero, and even this state is open to debate).

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.

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.

9. 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?

Aquaporins

Apertures

Orofices

Water channels

Aquaporins are membrane water channels that regulate the passage of water through cell membranes.

Explanation

Aquaporins are membrane water channels that regulate the passage of water through cell membranes.

10. Once molecules reach a dynamic equilibrium on either side of a membrane they stop moving.

True

False

This is false. With the exception of the theoretical "absolute zero" molecules are ALWAYS in motion.

Explanation

This is false. With the exception of the theoretical "absolute zero" molecules are ALWAYS in motion.

11. The thing that drives the diffusion of molecules are molecular collisions.

True

False

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.

Explanation

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.

12. What are "free" water molecules?

Water molecules that don't require energy to move across cell membranes.

Water molecules that are not bound to solutes (such as salt).

Water molecules that are bound to salt molecules.

Water molecules that are not connected to each other.

"Free" water molecules are 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).

13. Molecules are often said to: "move in constant random motion". Why do molecules appear to move that way? Choose the best answer.

Because molecules have kinetic energy.

Because molecules have potential energy.

Because molecules are constantly colliding with each other.

Because they move randomly due to the laws of physics.

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.

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.

14. If an animal cell was placed in a hypertonic solution, which answer best predicts what would happen?

The cell will shrivel and possibly die due to loss of water by osmosis.

The cell will expand and possibly die due to the gain of water by osmosis.

The cell will shrivel and possibly die due to loss of salt by diffusion.

The cell will expand and possibly die due to the gain of salt by diffusion.

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.

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.

15. Which answer best explains why the Gummy Bears from our lab were larger the next day, after being placed in distilled water?

Salt entered by osmosis from an area of high to lower concentration.

Gummy bears often eat sugar during the day and grow overnight.

A concentration gradient moved water from an area of low to higher concentration.

Water entered the bears by osmosis from an area of high to lower concentration.

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.

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.

16. 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.

True, because diffusion moves molecules from a high to low concentration.

False, because molecules cannot move across membranes by diffusion.

False, because diffusion moves molecules from a low to high concentration.

False, because molecules such as sugar are too large to move across cell membranes.

False, because energy is required for diffusion.

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).

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).

17. Water molecules have a net movement from an area of lower solute concentration to an area of high solute concentration.

True

False

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.

Explanation

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.

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?

Water breaks down the green dye/pigment used to color the bear.

The green dye/pigment diffused from an area of high to an area of lower concentration.

As water moved into the bear, it pushed the green dye/pigment out.

Green gummy bears possess chlorophyll for photosynthesis... this chlorophyll breaks down rapidly in the presence of water.

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).

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).

19. What term means the concentrations of a molecule are equal on both sides of a membrane?

A.) Hypertonic

B.) Hypotonic

C.) Isotonic

D.) Dynamic equilibrium

Both "C" and "D' are correct

Both the terms "Isotonic" and "Dynamic Equilibrium" describe conditions where the concentrations of a molecule are equal on both sides of a membrane.

Explanation

Both the terms "Isotonic" and "Dynamic Equilibrium" describe conditions where the concentrations of a molecule are equal on both sides of a membrane.

20. Diffusion stops if there is no concentration gradient.

True

False

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.

Explanation

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.