Diffusion, osmosis, and tonicity

Which of the following statements about diffusion is correct?

• It requires an expenditure of energy by the cell.
• It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
• It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
• It is a passive process in which molecules move from a region of lower concentration to a region of higher concentration.

Red blood cells typically have an internal solute concentration of 2%. A red blood cell is placed in the beakers below containing different concentrations of solutes. Which of the cells would have the lowest rate of diffusion?

• A
• B
• C
• D

Which of the following would result in a higher rate of diffusion? Check all that apply.

• Switching dyes from Acid blue 45 with a molecular weight of 311.1 grams/mole to Brilliant blue R, which has a molecular weight of 712.9 grams/mole.
• Decreasing the viscosity of a solvent from 15 cP to 1 cP.
• Pulling a solution out of the refrigerator (3 °C) and bringing it to room temperature (23 °C).
• For an oxygen molecule diffusing within a cell towards the mitochondria, decreasing the water content of the cytoplasm by 5%.
• Switching food sources for a bacteria from the disaccharide sucrose to the monosaccharide fructose

Which of the following is NOT true about osmosis?

• It is the movement of water from a low concentration to a high concentration.
• The direction of water movement is determined by the relative osmolarity of the two solutions.
• It is the movement of water across a semipermeable membrane.
• It does not require energy.

Which of the following substances has the highest osmolarity?

• Pure water

• 2% NaCl in water

• 4% fructose in water

• 1% NaCl + 4% fructose in water

Which of the following solutions has the highest water concentration?

• 2% glucose and 5% sucrose in water.
• 15% NaCl in water.
• 15% glucose in water.
• 2% KCl in water.

A student was studying the responses of cells to solutions of varying salt concentrations. Which scenario(s) below would cause no change in the cell in the center?

• A
• B
• C
• D

Tags

NGSS.HS-LS1-3

A mixture of 3% starch and 3% glucose was placed into a dialysis-tubing bag. Dialysis tubing has small holes which let some things through and block others, so it acts as a semipermeable membrane. The bag initially weighed 22 g. It was then placed into a beaker of distilled (pure) water. After 3 hours, the bag weighed 30 g. Glucose was detected in the water outside the bag, but starch was not. Which of the following is true about the semipermeable membrane of the dialysis tubing in this experiment?

• The holes in the dialysis tubing were smaller than glucose and starch, but larger than water.
• The holes in the dialysis tubing were larger than glucose and water, but smaller than starch.
• The dialysis tubing didn’t allow water to pass through the membrane.
• The dialysis tubing allowed all the molecules in the bag to pass through the membrane.

An accident victim has lost a lot of blood due to a serious injury. Replacement of the lost body fluids with a hypertonic saline solution would have which of the following results?

• The victim’s red blood cells would be unable to exchange water with the saline solution.
• The victim's red blood cells will shrivel up.
• The victim's red blood cells will swell and lyse.
• The victim’s red blood cells will be unaffected.

Tags

NGSS.HS-LS1-3

Hasini takes some strips of potato and puts them in two different solutions. After an hour, the potatoes in beaker one stayed firm and upright and the potatoes in beaker 2 became soft and began to droop. Which of the following is most likely true about the solutions in the beakers relative to the potato cells?

• Beaker 1 is hypotonic to the potato cells, beaker 2 is hypertonic
• Beaker 1 is hypertonic to the potato cells, beaker 2 is hypotonic
• Both beakers are isotonic to the potato cells
• The potatoes in both beakers have a higher concentration of solutes than the solvents.