Review of NYS Lab Diffusion and Membranes

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Review of NYS LabDiffusion and Membranes
Name ___________________

• Adapted from materials created by Mike Comet

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Part 1- Diffusion through a Membrane

• Diffusion
• Osmosis
• Selectively permeable
• Hypertonic

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Part 1- Diffusion through a Membrane

• Isotonic
• Hypotonic
• Saline
• Molecule size

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Part 1- Diffusion through a Membrane
1. What does the tubing represent?
2. What substances did you pour inside of the
tubing?
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Part 1- Diffusion through a Membrane
3. What was added to make the liquid outside the
cell amber colored?
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Part 1- Diffusion through a Membrane
4. Why does the inside of the cell turn purple
or black?
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Part 1- Diffusion through a Membrane
5. Did starch move from inside the cell to
outside the cell? Explain how you know.
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Part 1- Diffusion through a Membrane
6. Did glucose move from inside the cell to
outside the cell? Explain how you know.
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Part 1- Diffusion through a Membrane

• Describe the test for the presence of starch in a
  sample.

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Part 1- Diffusion through a Membrane

• Describe the test for glucose in a sample.

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Part 1- Diffusion through a Membrane
7. After placing 10 drops of the amber solution
into a test tube, what do we add to it?
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Part 1- Diffusion through a Membrane
8. After adding the glucose indicator solution
(blue) what do we do with the test tube?
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Part 1- Diffusion through a Membrane
9. If there is glucose in the solution, what will
happen to the blue color after heating the tube
for 2-3 minutes?
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Part 1- Diffusion through a Membrane
10. The blue color changed to orange. This means
that what substance is in the test tube?
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Part 1- Diffusion through a Membrane
starch
glucose
C6H12O6
11. Glucose indicator solution was added to these
test tubes, and then the tubes were heated. Which
will change color?
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Analysis Questions

• What substance(s) diffused through the membrane?
• What substance(s) did not diffuse through the
  membrane?
• Explain why some substances were able to pass
  through the membrane while others were not able
  to.

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Analysis Questions

• Explain why some substances were able to pass
  through the membrane while others were not able
  to.

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Analysis Questions
Final State (after 20 minutes)
Initial State
In both diagrams above, using letters I (starch
indicator), G for Glucose, and S for starch,
indicate the areas where each of these molecules
are located.
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Part 2 - Osmosis

1. Why do you think we used red onions for this
   experiment?

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Part 2 - Osmosis

1. How do you prepare a wet mount for microscope
   examination of a sample?

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Part 2 - Osmosis

• Onion cell at 400x in a isotonic solution
• Label the cell wall, cell membrane, cytoplasm

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Part 2 - Osmosis

• Onion cell at 400x in a hypertonic solution
• Explain the change observed in the cell.

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Part 2 - Osmosis

• Onion cell at 400x after distilled water was
  added following the salt solution
• Explain the change observed in the cell.

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Analysis Questions

• What test would you need to perform to prove it
  is the combination of glucose and the Glucose
  Indicator Solution that changes color when heated
  and not just the glucose or the Glucose Indicator
  Solution alone? Support your answer with an
  explanation.

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Analysis Questions

• During Part 1 of this laboratory activity, one
  group of students poured starch indicator
  solution in the cell and filled the beaker with
  starch and glucose solution. State how their
  results would be different than a group of
  students who followed the direction carefully.

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Analysis Questions

• Some state roads are slated heavily in winter,
  creating an environmental problem. Based on
  observations you made in this lab activity,
  explain how organisms could be harmed by high
  levels of salt from roadways.

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Analysis Questions

• When a person in the hospital is given fluid
  intravenously (an I.V.), the fluid id typically a
  saline (salt) solution with about the same water
  concentration as human body tissues. Explain how
  the use of distilled water in place of the saline
  solution would be expected to upset the patients
  homeostasis. Your answer should refer to the
  process of diffusion.

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Analysis Questions

• Many fresh-water one celled organisms have
  structures called contractile vacuoles. These
  structures collect and pump out excess water that
  accumulates in the cell. Name the process that
  causes water to flow into these organisms.
  _____________ Explain why contractile vacuoles
  would be of little value to one-celled organisms
  living in the ocean (salt water).

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Controlling water

• Contractile vacuole in Paramecium

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Analysis Questions

• Popcorn sold at most movie theaters is very
  salty, causing people to become thirsty and buy
  soft drinks. Based on what you learned in this
  lab, explain why the salty popcorn causes this
  thirst.

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Analysis Questions

• In many animals, glucose, rather than starch is
  transported by the blood through the body to all
  of the cells. Starches in many foods are
  digested to yield glucose. Based on what you
  learned in this activity, explain why the
  digestion of starch to glucose is necessary.