Review of NYS Lab
Diffusion and Membranes
Name: ___________________
Adapted from materials created by Mike Comet
1
Part 1- Diffusion through a Membrane
• Diffusion
• Osmosis
• Selectively permeable
• Hypertonic
2
Part 1- Diffusion through a Membrane
• Isotonic
• Hypotonic
• Saline
• Molecule size
3
Part 1- Diffusion through a Membrane
1. What does the
tubing represent?
2. What substances
did you pour inside
of the tubing?
4
Part 1- Diffusion through a Membrane
3. What was added
to make the liquid
outside the “cell”
amber colored?
5
Part 1- Diffusion through a Membrane
4. Why does the
inside of the
“cell” turn purple
or black?
6
Part 1- Diffusion through a Membrane
5. Did starch move
from inside the cell
to outside the cell?
Explain how you
know.
7
Part 1- Diffusion through a Membrane
6. Did glucose
move from inside
the cell to outside
the cell? Explain
how you know.
8
Part 1- Diffusion through a Membrane
Describe the test for the presence of starch
in a sample.
9
Part 1- Diffusion through a Membrane
Describe the test for glucose in a sample.
10
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?
11
Part 1- Diffusion through a Membrane
8. After adding the
glucose indicator
solution (blue)
what do we do
with the test tube?
12
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?
13
Part 1- Diffusion through a Membrane
10. The blue color
changed to
orange. This
means that what
substance is in the
test tube?
14
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?
15
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.
16
Analysis Questions
• Explain why some substances were able
to pass through the membrane while
others were not able to.
17
Analysis Questions
Initial State
Final State (after 20
minutes)
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.
18
Part 2 - Osmosis
1. Why do you think we
used red onions for
this experiment?
19
Part 2 - Osmosis
2. How do you prepare a wet mount for
microscope examination of a sample?
20
Part 2 - Osmosis
Onion cell at 400x in a
isotonic solution
•
Label the cell wall,
cell membrane,
cytoplasm
21
Part 2 - Osmosis
Onion cell at 400x in a
hypertonic solution
4. Explain the change
observed in the cell.
22
Part 2 - Osmosis
Onion cell at 400x after
distilled water was
added following the
salt solution
5. Explain the change
observed in the cell.
23
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.
24
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.
25
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.
26
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
patient’s homeostasis. Your answer should refer to the
process of diffusion.
27
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).
28
Controlling water
• Contractile vacuole in Paramecium
29
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.
30
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.
31