Question Sheet for Diffusion and Osmosis – Station 4

Question Sheet for Diffusion and Osmosis – Station 4

  1. What does water do when a cell is put in a hypotonic solution?
  • In a hypotonic solution, water will move from the region of high concentration, the solution, to the low concentrated areas in the cell, causing it to swell.


  1. What does water do when a cell is put in a hypertonic solution?
  • In a hypertonic solution, water will move from the cell and into the low concentration region of the solution.


  1. What does water do when a cell is put in an isotonic solution?
  • Here, there is no record of movement as all regions have the same concentration of water.


  1. What tonicity do animal cells prefer and why?
  • Animal cells prefer isotonic tonicity because they can afford to take up too much water or lose it. They do not have a cell wall
  1. What happens to an animal cell in a hypotonic solution?
  • An animal cell introduced to a hypotonic solution will start to absorb water, as it will move from the region of high concentration and into the cell. The cell will, therefore, turgid and burst after some time.
  1. What tonicity do plant cells prefer and why?
  • Plants cells prefer hypotonic environments as they can absorb more water, and store it for future use.
  1. What is the difference between a turgid and a flaccid plant cell?
  • A turgid cell is full of water which happens when it is put in a hypotonic solution. On the other hand, a cell becomes flaccid when placed in a hypertonic solution and water moves out of and into the solution causing it to appear weak and shrunk.


  1. Why does water diffuse from low solute concentration to high solute concentration?
  • Water can move from a region of low solute concentration to a highly concentrated region because it has a concentration gradient. Water molecules will move from where they are in high concentrations to regions where the solute is in high concentration.


  1. What are the three things that can happen as hydrostatic pressure increases?
  • As hydrostatic pressure increases within a plant cell, it swells up and becomes turgid. Plants harness this pressure and may use it, the opening of stomata, leaf positioning or growth.


  1. What is osmolarity?
  • The total number of moles of solute in a given solution of water.


  1. How many grams of NaCl would you need to make 500 ml of a 100 mM solution? Note: the atomic weight of NaCl is 58.

58 grams = 1 M

?          =0.1

= 5.8/2

= 2.9grams

12 How many grams of glucose would you need to make 500 ml of a 100 mM solution?

Note: the atomic weight of glucose is 180.

180grams = 1M

90grams = 1M for half a liter

?        =0.1M

= 9 grams of glucose

What is the tonicity (hypotonic, hypertonic, or isotonic) of the solution in each of the five beakers?



  1. Solution 1 –Isotonic


  1. Solution 2 –


  1. Solution 3 –Hypertonic


  1. Solution 4 –


  1. Solution 5 – Hypotonic



  1. Which of the beakers (1 to 5) had the 1.2% NaCl solution?
  • 1 – The solution was isotonic to the animal cell.
  1. How would a red blood cell respond differently in a 5% sucrose solution versus a 5% glucose solution? Remember that sucrose is made up of two sugar molecules and, has about double the atomic weight of glucose.

The 5 % sucrose solution would be isotonic to the red blood cells. On the other hand, the 5% glucose would be hypertonic leading to the animal cell losing water to it.


Question Sheet for Membrane Transport – Station 5


  1. What large molecules form two layers to form the plasma membrane?
  • Negatively charged phosphates and fatty acid chains


  1. In passive transport, molecule and ions flow from __high_______ concentration to __low_______ concentration.


  1. Why does passive transport not require an input of energy?
  • Passive transport does not require energy because molecules move down the concentration gradient. The process also increases the state of disorder.


  1. What is the name for the type of channel transport protein in the model?
  • They are channel transport proteins for water.


  1. What molecule do you think is moving through the channel transport protein (note it is a common molecule with two small atoms attached to one larger atom)?
  • Water is the molecule moving through the channel transport protein-Oxygen bound to two hydrogen molecules.


  1. How does a carrier transport protein differ from a channel transport protein?


  • Unlike channel transport proteins which are simple tunnels, carrier proteins need to change their shape every time to facilitate the movement of molecules.


  1. How does the glucose molecule get through the carrier transport protein in the model?
  • The glucose molecule can get into the cell because the carrier transport molecule changes shape to allow the process.


  1. How does active transport differ from passive transport?
  • Active transport is the movement of molecules against the concentration gradient while passive transport allows the transport of ions down the gradient, from a high concentration to a region of low concentration.
  • Active transport uses energy while passive transport does not.


  1. Why does active transport require energy?
  • The process requires energy because it involves the pushing of molecules against the concentration gradient, thereby reducing entropy.


  1. What molecule usually provides the energy used in active transport?
  • Adenosine Triphosphate – ATP


  1. How many sodium ions are pumped out and how many potassium ions pumped in by the sodium pump?

For every three molecules of sodium pumped out of the cell, two potassium molecules get pumped out.


  1. What does ATP dissociate into when it releases energy?

When ATP releases energy, it dissociates into ADP and an inorganic Phosphate.


  1. How does a proton pump differ from a sodium-potassium pump?

The sodium-potassium pump functions by pumping molecules both inside and outside, while the proton pump only operates one way.

Unlike the sodium-potassium pump that pumps ions inside and outside, the proton one only works one way, out.

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