Biology 3
Merritt
REVIEW QUESTIONS: Cells, Membranes, and Membrane Transport
What is a prokaryote, a eukaryote? How can you recognize them? What structures are characteristic of each
cell type? What structures do they have in common? What structures differ?
Are plants prokaryotes or eukaryotes? How about animals? What structures are characteristic of each cell
type? What structures do they have in common? What structures differ?
Be able to identify all cell structures by appearance. Know the function of each structure. And know what cell
type (prokaryote, eukaryote, animal, plant) contains each structure.
What is the endomembrane system? What structures are part of it? What functions does the endomembrane
system carry out? How do these structures work together to accomplish these functions?
What are the relative sizes of those thingies on the handout I gave you? Knowing the rank order is sufficient.
What components make up biological membranes? How are these components arranged?
Why do the phospholipids arrange themselves as they do? What holds the phospholipid bilayer together?
The proteins in membranes are classified into two categories according to their position in the membrane. What
are these categories? What property of a protein determines its position in the membrane? What about the
protein determines this property?
What is the term for a membrane protein with a carbohydrate attached? What is the function of these
protein/carbohydrate complexes?
What kinds of molecules can pass through the bilayer unaided? What are some examples of these molecules?
What kinds of molecules can't pass through unaided? What are some examples of these molecules?
What do the following terms mean: solution, solvent, and solute?
What is the term for the total solute concentration in a solution? What is the term for a solution that has a
higher solute concentration than another? What is the term for a solution that has a lower solute
concentration than another? What is the term for two solutions that have equal solute concentration?
What do the following terms mean: simple diffusion, facilitated diffusion, osmosis, and active transport? What
is meant when we say a process is passive? Which transport processes are passive? Which require energy?
If energy is required, where does it come from? Which transport processes require transport proteins?
Which don't? What is meant by a concentration gradient? Which transport processes operate down a
concentration gradient? Which operate up? When does transport stop in each of the processes? Does
transport actually stop, or does material continue to cross the membrane? Explain your answer.
What are aquaporins? What is their function? What transport process do they function in?
What is endocytosis? exocytosis?
BE SURE TO STUDY THE CELL STRUCTURE & MEMBRANE TRANSPORT STUDY GUIDES
1
2
3
4
5
6
7
8
9
10 m
Human height
Length of some
nerve and
muscle cells
0.1 m
Chicken egg
1 cm
Frog egg
100 µm
Most plant and
animal cells
10 µm
Nucleus
Most bacteria
1 µm
100 nm
Mitochondrion
Smallest bacteria
Viruses
10 nm
Ribosomes
Proteins
Lipids
1 nm
Small molecules
0.1 nm
5
1
1
Electron microscope
1 mm
Surface area increases while
total volume remains constant
Light microscope
1m
Unaided eye
Fig. 6-2
Total surface area
[Sum of the surface areas
(height width) of all boxes
sides number of boxes]
Total volume
[height width length 
number of boxes]
Surface-to-volume
(S-to-V) ratio
[surface area ÷ volume]
6
150
750
1
125
125
6
1.2
6
Atoms
Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Bacterial
chromosome
Cell wall
Capsule
0.5 µm
(a) A typical
rod-shaped
bacterium
Flagella
(b) A thin section
through the
bacterium
Bacillus
coagulans (TEM)
10
Fig. 6-9a
Nuclear
envelope
ENDOPLASMIC RETICULUM (ER)
NUCLEUS
Nucleolus
Flagellum
Rough ER
Smooth ER
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome
Fig. 6-9b
NUCLEUS
Nuclear envelope
Nucleolus
Chromatin
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Ribosomes
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
CYTOSKELETON
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
Cell wall
Plasmodesmata
Wall of adjacent cell
11
Fig. 6-10
Nucleus
1 µm
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Surface of
nuclear envelope
Rough ER
Ribosome
1µm
0.25 µm
Close-up of nuclear
envelope
Pore complexes (TEM)
Nuclear lamina (TEM)
Fig. 6- 11
Cytosol
Intermembrane space
Outer
membrane
Endoplasmic reticulum (ER)
Free ribosomes
Free
ribosomes
in the
mitochondrial
matrix
Bound ribosomes
Large
subunit
Small
subunit
0.5 µm
TEM showing ER and ribosomes
Inner
membrane
Cristae
Matrix
Diagram of a ribosome
0.1 µm
Ribosomes
Stroma
Inner and outer
membranes
Granum
Thylakoid
1 µm
12
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
cis face
(“receiving” side of
Golgi apparatus)
0.1 µm
Cisternae
Transitional ER
Rough ER
200 nm
trans face
(“ shipping” side of
Golgi apparatus)
TEM of Golgi apparatus
Fig. 6 -16-3
Nucleus
Rough ER
Smooth ER
cis Golgi
Plasma
membrane
trans Golgi
Nucleus
1 µm
Vesicle containing
two damaged organelles
1 µm
Mitochondrion
fragment
Peroxisome
fragment
Lysosome
Lysosome
Digestive
enzymes
Plasma
membrane
Lysosome
Peroxisome
Digestion
Food vacuole
Vesicle
(a) Phagocytosis
Mitochondrion
Digestion
(b) Autophagy
13
14
15
Fibers of
extracellular
matrix (ECM)
Glycoprotein
Carbohydrate
Glycolipid
EXTRACELLULAR
SIDE OF
MEMBRANE
Cholesterol
Microfilaments
of cytoskeleton
Peripheral
proteins
Integral
protein
CYTOPLASMIC SIDE
OF MEMBRANE
ER
1
Fig. 7-2
Transmembrane
glycoproteins
Secretory
protein
Glycolipid
Golgi
2
apparatus
Vesicle
WATER
Hydrophilic
head
3
4
Hydrophobic
tail
Secreted
protein
WATER
Plasma membrane:
Cytoplasmic face
Extracellular
face
Transmembrane
glycoprotein
Membrane glycolipid
Fig. 7- 16-7
EXTRACELLULAR
FLUID
[Na +] high
[K+] low
Na+
Na +
Na
Na+
Na+
Na+
Na+
+
Na +
CYTOPLASM
Na+
1
[Na +] low
[K+] high
P
ADP
2
ATP
P
3
K+
K+
K+
K+
K+
P
K+
6
P
5
4
16
Biology 3
Merritt
Name
Period
STUDY GUIDE: Cell Structure
This study guide introduces the major components of prokaryotic and eukaryotic cells. I will require you to
know both the function and structure (i.e., what it looks like) of each component. You might find it useful to
quickly sketch each component. Alternatively, you might sketch an entire cell and include the components in it.
General
1. What is a cell?
2. What is an organelle? (Note: I want a definition of an organelle, not examples.)
Prokaryotes
3. What are prokaryotes? Define this group of organisms.
4. What is the nucleic acid in prokaryotes?
Eukaryotes
5. What is a eukaryote? Define this group of organisms.
6. In the table below, identify the components found in prokaryotes and eukaryotes (animals and plants).
7. What are two similarities
Eukaryote
between prokaryotic and
Cell Structure
Prokaryote Animal
Plant
eukaryotic cells?
Cell Wall
Plasma Membrane
Pilus (pl. pili)
Flagellum (pl. flagella)
8. Do eukaryotes contain
Cytoplasm
organelles? Do prokaryotes?
Cytosol
Ribosome
Nucleoid
Naked DNA
9. What are three differences
Plasmid
between animal and plant
Nucleus
cells?
Rough Endoplasmic Reticulum (rER)
Golgi Apparatus
Vesicle
Lysosome
Mitochondrion
Chloroplast
Vacuole
10. The endomembrane system consists of ER, Golgi apparatus, lysosomes, and vesicles. How do the
organelles of the endomembrane system work together to move substances out of the cell? You might find
it useful to diagram the process.
17
STUDY GUIDE: Organelle Flash Cards
Cell Wall
Plasma Membrane
Cytoplasm
Cytosol
Ribosome
Pilus (pl. pili)
Flagellum (pl. flagella)
Nucleoid
Naked DNA
Plasmid
Nucleus
Rough Endoplasmic Reticulum (rER)
Golgi Apparatus
Vesicle
Lysosome
Mitochondrion
Chloroplast
Vacuole
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
Prok / Euk ( P / A )
18
Biology 3
Merritt
Name
Period
STUDY GUIDE: Membrane Transport Processes
1. What is the structure of membranes? Diagram a portion of a
membrane to the right, showing the main constituents we
talked about in lecture. Label the constituents and regions that
are hydrophilic or hydrophobic.
2. What do the following terms mean?
Solution
Solvent
Solute
3. a. What kinds of molecules can pass through the phospholipid bilayer unaided?
b. What kinds of molecules cannot pass through the phospholipid bilayer unaided?
4. Consider the following molecules: O 2, K+, H 2O, glycerol. Which of these molecules can move across the
phospholipid bilayer unaided? Explain your answer.
5. Which transport processes require transport proteins?
6. Which transport processes use energy?
What is the source of energy?
7. Which transport processes move molecules down their concentration gradient?
8. For each of the diagrams below, decide which transport process(es) will occur. Justify your answer. Then
draw the equilibrium state that results after the processes have occurred.
Bilayer permeable to A
A
A
A
A A
A A
A
A
A
A
A
A
A
A
Bilayer permeable to A
A
A
A
A
A
A
A
A
A
19
A
A
A
A transport
protein
A
A
Bilayer impermeable to A
A is moved out of cell
A
A
A
A
A A
A
Bilayer permeable to A and B
[inside] = [outside]
B B B
A
B
B
A
A
A
B
A
A A
A
A
B
A
B
A
B
B B
B B B
A
A
B
B
A
A
B A
A
A A
A
A
B
A
B
A
B
B B
A
A transport
protein
A
A
A
A A
A A
A
A
A
A
A
Bilayer impermeable to A and B
[inside] = [outside]
Bilayer impermeable to A
A is moved out
A
A
A
A A
A
A A
A
A
A
A
A A
A
A
B
A
B B B A
B
B
A
B
A
A
A
A
A
B transport
protein
Bilayer impermeable to A
Bilayer impermeable to A, permeable to B
[inside]=[outside]
20
A
A A
B
A
A transport
protein
Bilayer impermeable to A and B
[inside] = [outside]
A
B B B A
A
A A
A
B
A
A
A
A
A
9. Refer to the diagram of the U-tube setup below to answer the questions below. The solutions in the two
arms of the U-tube are separated by a membrane that is permeable to water and glucose but not sucrose.
A
B
2 M sucrose
1 M glucose
1 M sucrose
2 M glucose
Differentially
permeable membrane
a. Initially, is the solution in the A arm hyperosmotic, hypoosmotic, or isoosmotic to the solution in the B
arm? Explain your answer.
b. What happens in the arms over time? What solutes move? Does the fluid level change? Justify your
answer, explaining the process(es) leading to any changes.
21
22
23
Biology 3
Merritt
Name
Period
LAB: Using the Compound Microscope
Parts of the compound microscope
Magnification
Objective
Low
Magnification
Eyepiece Objective
Total
Medium
High
Using the Compound Microscope
Obtain a prepared slide. Following the steps below, look at the specimen under low, medium, and high power.
Call me over to check each power.
1. Turn to low power objective
2. Center object on stage opening
3. Turn coarse adjustment to bring objective
lens as close as possible to stage
4. Turn coarse adjustment back to focus
5. Re-center object
6. Turn to medium power objective
7. Turn coarse adjustment to focus
8. Re-center object
9. Turn to high power objective
10. Turn fine adjustment to focus
Orientation of Objects
Cut out a portion of an advertisement that contains the letter e in lower case. Put the ad on a slide and place a
cover slip over it. (This is called a dry mount because you don’t add water to the specimen.) Orient the e so
that you can read it normally when you look at it from the side (i.e., not through the microscope). Now look
under low power.
 Draw what you see through the microscope, highlighting the orientation of the letter.
 How does the view of the letter through the microscope compare to its actual orientation?
Measuring Field Diameter
Use a ruler to measure the field diameter under the 4X and 10X objectives. Record your results.
4X objective
mm /
µm
10X objective
mm /
µm
Why didn’t I ask you to measure the field diameter under the 40X objective? If you’re unsure, try it.
Based on the measured field diameter under the 4X objective, calculate the field diameters under the 10X and
40X objectives.
10X objective
mm /
µm
40X objective
mm /
µm
 How do the measured and calculated field diameters under the 10X objective compare? Which do you
think is more accurate? Why?
24
Estimating Size of Objects
You can estimate the size of an object by comparing it to the known diameter of the field of view. To do this,
estimate the number of objects it would take to cross the field at its widest point (i.e., the diameter). For
example, if 5 objects fit across the field of view and you have determined that the field diameter is 1000 µm,
then the object is 1/5 of 1000 µm or 200 µm. You can use the field diameters above to estimate the size of
objects under all magnifications.
Make a dry or wet mount of some small specimen such as a hair. Make a quality drawing of the object. Follow
the procedure above to estimate its size. Show your calculation.
Drawing Magnification
Participate in the class discussion to learn about drawing magnification and how to calculate it. Take notes so
you will be able to calculate it later.
What is the drawing magnification of the object you measured? Show your calculation.
Add drawing magnification and a scale bar to your drawing.
25
LAB: Cell Structure
OBJECTIVES
 determine whether a cell is prokaryotic or eukaryotic based on its structure
 prepare a wet mount to view cells with a compound microscope
 relate the structure to the function of cellular organelles visible with the light microscope
 determine whether a eukaryotic cell is an animal or plant
PRE-LAB QUESTIONS.
1. Are bacteria unicellular or multicellular organisms? What about plants? Animals?
2. Are the cells of bacteria all the same, or are some specialized for particular functions? What about the cells
of plants? animals?
3. What is the primary function of leaves? Name the chemical process that occurs in leaves.
4. Given the function of leaves, what organelle would you expect to find in them?
5. Would you expect to find this organelle in roots? Explain your answer.
PROKARYOTES
Bacteria
Yogurt is a nutrient-rich culture of bacteria that is acidic and keeps well. Lactobacillus, a bacterium commonly
used to make yogurt, is adapted to live on lactose (milk sugar). Historically, Lactobacillus has been used in
many parts of the world by peoples deficient in lactase, an enzyme that breaks down lactose. Many Middle
Eastern and African cultures use yogurt in their diet instead of milk because it is more digestible.
1. Place a tiny dab of yogurt on a microscope slide.
2. Add a drop of stain (methylene blue) next to the yogurt, mix the two fluids with a toothpick, add a
coverslip, and examine the yogurt under high power using the compound microscope.
3. Draw a few bacteria cells.
4. Estimate the size of a bacterium, calculate the drawing magnification, and include a scale bar.
5. Wash the slide and coverslip.
Questions
1. Can you see any structures inside the bacteria cells?
EUKARYOTES
Plant Cells
Moss Leaf
1. Using forceps, remove a young leaf from the tip of a sprig of moss.
2. Place the leaf in a drop of water on a microscope slide. Add a coverslip. Do not let the leaf dry—add
another drop of water if necessary.
3. Examine the leaf under high power using the compound microscope.
4. Draw a few moss leaf cells.
5. Estimate the size of a cell, calculate the drawing magnification, and include a scale bar.
6. Test the moss leaf for starch. Lift the coverslip, add a drop of iodine solution to the onion, and replace
the coverslip. Look at the cells again under high power. Record your results.
7. Wash the slide and coverslip.
Potato
1. Using a razor blade, follow your teacher’s instructions to cut a thin wedge-shaped section of potato.
2. Rinse the wedge, place it on a slide, add a drop of water, and place a coverslip on top.
3. Examine the thin portion of the pototo under low power using the compound microscope. When you
can see individual cells clearly, go to medium power. (Do not use high power.)
4. Draw a few potato cells.
5. Estimate the size of a cell, calculate the drawing magnification, and include a scale bar.
6. Test the potato for starch. Lift the coverslip, add a drop of iodine solution to the onion, and replace the
coverslip. Look at the cells again under high power. Record your results.
7. Wash the slide and coverslip.
26
Radish
1. Prepare a thin section of radish following the procedure you used for the potato.
2. Draw a few radish cells in the circle below.
5. Estimate the size of a cell, calculate the drawing magnification, and include a scale bar.
3. Test the radish for starch as directed above.
4. Wash the slide and coverslip.
Questions
1. Note the thick layer surrounding each plant cell. What is this structure? What is its function? What
material makes it up? To which macromolecule class does the material belong?
2. Can you see the cell membrane? Why or why not?
3. Some of the cells contain small green spheres. Which cells contain them? Which do not? What are these
structures? What is their function? Can you explain why they are in some of the cells and not in others?
4. Which cells contain starch? Where is the starch located? Is it spread throughout the cell, or is it
concentrated in certain areas?
5. What is the function of moss leaf cells? Do the organelles present reflect this function?
6. What is the function of potato tuber cells? Do the organelles present reflect this function? Does the
presence of starch reflect this function?
7. Based on your results, are the cells of the radish specialized to perform the same function as the cells of the
potato? Explain your answer.
Animal Cells
Muscle
1. Bring a clean slide to your teacher, and obtain a thin section of beef muscle.
2. Add a drop of stain (methylene blue) to the specimen, and place a coverslip on top.
3. Using your finger or a pencil eraser, gently squash the specimen. You need to spread the muscle fibers
apart so you can see them better. Err on the side of squashing too gently—you can always squash more,
but you can’t put the fibers back together once you’ve squashed too hard and destroyed them.
4. Using a compound microscope under low power, look at the fibers. Go to medium and then high power.
If you’ve squashed just right, you should see something like the top picture in Figure 38–10 (p. 843).
5. Draw a few muscle cells. Include a scale bar and the drawing magnification.
6. Wash the slide and coverslip
Fat Cells
1. Bring a clean slide to your teacher, and obtain a thin section of beef fat.
2. Add a drop of water, and place a coverslip on top. Do not add stain or squash the specimen.
3. Using a compound microscope under low power, look at the cells. Go to medium and then high power.
4. Draw a few fat cells.
5. Estimate the size of a cell, calculate the drawing magnification, and include a scale bar.
6. Wash the slide and coverslip, and return them to where you got them.
Questions
1. Describe the appearance of muscle tissue.
2. Do you see any organelles in the muscle cell? If so, which ones?
3. What structures make the muscle appear banded or striated?
4. Describe the appearance of fat tissue.
5. Do you see any organelles in the fat cells? If so, which ones.
6. Is the fat stored inside or outside of the cells? How can you tell?
27
LAB: Using Glass Pipettes
OBJECTIVES
 Practice using glass pipettes
INTRODUCTION
Glass pipettes are very handy for dispensing exact volumes of liquids. They are easy to use, but they must be
used correctly to ensure accuracy. This lab will ensure that you understand how to use pipettes correctly.
Pipettes have a maximum volume (in mL) written on them. This volume is subdivided to enhance the accuracy
of measurement. For example, a pipette labeled 10 mL in 1/10 means that the maximum capacity of the pipette
is 10 ml and the smallest gradations are 1/10 mL.
Pipettes must ALWAYS be used with a pipette pump to draw liquids into the pipette. The liquid should
NEVER come in contact with the pump itself. NEVER invert the pipette allowing liquid to run into the pump.
TEST YOUR PIPETTING ACCURACY
You will work in pairs, sharing a pipette. However, you will each pipette separately and record only your own
data.
Using the instructions below, EACH partner should obtain and weigh a plastic weigh boat. Pipette 0.5 mL (=500
L = 0.500 g) of distilled water into your boat and reweigh the boat. Subtract the initial weight from the final
weight to obtain the weight of the water. Drain the water from the boat, reweigh it, and repeat the procedure four
more times. The calculated weights of the water should vary by only 0.010 g (10 L). If the water masses vary
by more than 
g, you should redo the exercise until you are pipetting accurately.
1.
Attach a pipette pump to a 1 mL pipette. Use your thumb to turn the knob down until the plunger is raised
1-2 cm. You will need this extra volume of air to aid in expelling the entire sample.
2.
Holding the pipette pump in one hand and the pipette in the other, place the pipette tip into the sample.
Turn the knob down slowly, drawing the liquid up into the pipette, until the miniscus reaches the desired
volume. Leaving the tip in the liquid, release the knob. If the liquid rises or falls, use the knob to make
minor adjustments to the volume so that the miniscus is exactly on the desired volume when the knob is
released.
3.
Withdraw the pipette tip from the sample. Any liquid adhering to the outside of the tip must be removed
by carefully touching the side of the tip against the side of the reagent container.
4.
To dispense the sample, touch the tip end to the wall of the receiving vessel and SLOWLY turn the knob
up. If you turn the knob too quickly, some droplets of the sample will adhere to the inside of the pipette.
5.
Withdraw the pipette tip from the vessel by sliding the tip along the wall of the vessel, wiping off any
liquid that still adheres to the outside of the tip.
6.
Gently wipe the outside of the tip on a paper towel before drawing the next sample.
28
LAB: Transport Across Membranes, Part 1
Before coming to lab, read this entire lab description and review pp. 136-141 in Campbell.
OBJECTIVES

 Understand the concepts of osmosis, hypo-/hyperosmotic solutions, and cell lysis
 Determine the permeability of cell membranes to ions
 Practice using a spectrophotometer
Introduction
The plasma membrane controls what substances can enter or leave cells. In lecture, we are learning about
several different membrane transport mechanisms used by cells. In this lab we will study one of these
mechanisms in living cells. We will use mammalian red blood cells (RBCs), also known as erythrocytes, to
study the process of simple diffusion across the plasma membrane. RBCs have been the most commonly used
cells for studies on plasma membrane structure and transport. Read about the structure of erythrocytes in your
textbook (see p. 823 & Fig. 42.13) to determine why they have been the cell of choice for research on the
plasma membrane. RBCs are readily available from any easily subdued animals (including humans) but are
most commonly obtained commercially from sheep.
Recall the principles of simple diffusion. Molecules that can penetrate or readily pass through the membrane
can enter or leave the cell by simple diffusion in response to their concentration gradients. If a substance is at a
higher concentration outside the cell than inside the cell, and if that substance can cross the membrane freely,
then it will diffuse into the cell. What are the characteristics of molecules that can freely cross the membrane?
Name some molecules that you think can pass through the membrane.
Recall that cells are 90% water. The movement of water into and out of cells is a special case of simple
diffusion called osmosis. Water passes freely through cell membranes in response to its own concentration
gradient. It is hard to measure the concentration of water, however, so we usually measure the concentrations
of all the solutes instead. Since more solutes means less water, water will diffuse from a region of low solute
concentration (= high water concentration) into a region with a higher total solute concentration (= lower water
concentration). When comparing two different regions to each other, such as the inside vs. the outside of the
cell, the region with the higher concentration of total solutes is hyperosmotic and the region with the lower
concentration of total solutes is hypoosmotic. The osmosis of water is the basis of many physiological
functions in cells and organisms.
Pre-lab Questions
1. What are the characteristics of molecules that can freely cross the membrane? Name some molecules that
you think can pass through the membrane.
2. Why is an RBC an ideal cell for studying membranes?
3. If the 0.16 M NaCl solution is isoosmotic to the RBC cytoplasm, does this mean that the cytoplasm consists
of 0.16 M NaCl?
4. What is cell lysis?
+
-
5. Do you think that either Na or Cl would be able to cross the RBC membrane by simple diffusion? Why or
why not?
29
A. Blood Composition
Put a drop of whole blood on a slide and place a coverslip on top of it. Using a compound microscope, look at the blood
under high power. Draw a picture of what you see in your lab notebook.
B. Osmosis—Diffusion of Water Across a Cell Surface Membrane
In this part of the lab, you observe what happens when you add RBCs to saline solutions [NaCl(aq)] of different
concentrations. There are six solutions: a stock saline solution (0.160 M NaCl; labeled SS), four dilutions of the
stock solution (1/2 SS, 1/4 SS, 1/8 SS, 1/16 SS), and dH2O (labeled NS for no saline). The stock solution is
isoosmotic to the RBC cytoplasm. When RBCs are suspended in a solution of isoosmotic NaCl, the suspension
looks cloudy or turbid because the cells scatter light.
1. Obtain 6 large test tubes. Label each tube for one of the solutions (SS, 1/2 SS, 1/4 SS, 1/8 SS, 1/16 SS, and
NS). Add 4.5 mL of each solution to the tube with the same label.
2. Using a 1 mL pipette, pipette 0.5 ml stock blood solution into each large test tube. NOTE: Over time, the
RBCs will settle to the bottom of the beaker. If you do not resuspend the RBCs, your samples will contain
different numbers of RBCs and this will cause excess variability in your results. To resuspend the blood
cells, gently swirl the blood stock solution before removing each sample.
Observe each tube and record whether it is turbid or clear.
Now quantify your observations using a spectrophotometer. The spectrophotometer does pretty much what
your eyes do—it shines a light through the tube and measures how much of the light is scattered by the sample.
The amount of light scattered is measured in units of “optical density” or OD. Before taking a measurement,
the spectrophotometer must be calibrated to determine the maximum and minimum amount of light
transmission possible using these solutions. To calibrate the spectrophotometer, set the instrument to the
wavelength you plan to use (500 nm for this experiment), close the lid for the chamber that holds the sample,”
and adjust the instrument to 0% transmittance. Then insert a tube filled with stock saline solution and adjust the
instrument to 100% transmittance. After you have completed the calibration, switch the machine to the
ABSORBANCE mode (not transmittance) to take OD readings.
Transfer the solutions above, one at a time, into the spectrophotometer cuvette. Record the OD reading for each
of your tubes. Rinse the cuvette carefully between solutions.
Finally, look at the solutions using a compound microscope. Place a drop of fluid on a microscope slide, add a
cover slip, and observe the sample under high power. Record whether you see intact RBCs. Repeat this
procedure for each of the solutions.
Construct a graph showing the relationship between OD and salt concentration. Write a figure legend
for your graph.
Why were some of the solutions turbid and others clear? Explain what happened, using all three types of
data (turbidity, OD, and microscopy) to justify your answer.
Did salt (either Na+ or Cl- ) cross the red blood cell membrane in this experiment? Refer to your results to
justify your answer.
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LAB: Transport Across Membranes, Part 2
OBJECTIVES

 Understand the concepts of osmosis, hypo-/hyperosmotic solutions, and cell lysis
 Determine the permeability of cell membranes to glucose and ethanol
Pre-lab Questions
1. Do you think that ethanol (CH 3CH 2OH) or glucose (C6H12O 6) would be able to cross the RBC membrane by
simple diffusion? Why or why not?
2. If you place RBCs into distilled water, they lyse. If you place a plant cell in distilled water, it is fine. How
can a plant cell tolerate distilled water?
A. Simple Diffusion—Permeability of Membranes to Substances Other Than Water
In this part of the lab, you will experiment with isoosmotic solutions of other molecules to infer whether the RBC
membrane is permeable to each type of molecule. There are two stock solutions available to you for this part of the
lab: 0.32 M ethanol and 0.32 M glucose. Label 2 small test tubes with E and G for ethanol and glucose solutions.
How can a 0.16 M NaCl solution and a 0.32 M glucose or ethanol solution both be isoosmotic to an RBC?
Using a 1 mL pipette, pipette 0.5 ml of the blood solution into each tube. Then, using the labeled 5 mL pipettes,
add 4.5 ml of the appropriate solution (ethanol in the E tube, etc.). Record the outcome (turbid or clear) and
your inferences about the permeability of the membrane to each of these molecules.
What is the relationship between solution turbidity and molecule penetration?
What series of events occurred that lead to the results you obtained? Explain the process, including all transport
processes.
B. Plasmolysis
So far, you’ve been concerned with cells in isoosmotic or hypoosmotic solutions. What happens to a cell in a
hyperosmotic solution? If the surrounding solution has a higher solute concentration than inside the cell, water
will leave the cell by osmosis and the cell will shrink. This shrinking process is called plasmolysis.
When placed in a hyperosmotic solution, at what internal solute concentration does a cell stop shrinking?
Place a single leaf of Elodea on a glass slide, add a drop of distilled water, and add a coverslip. Observe the
leaf under the 40X objective. Leaves of Elodea are two cell layers thick. Use the fine focus to focus on the
upper cell layer. Most of the cytoplasm is pressed against the outside of the cell surrounding the central vacuole
in these cells.
Make a neat drawing of a few of the cells, including all the detail you can see. Label the cell wall, cytoplasm,
and a chloroplast. Include an informative title and the magnification.
How are the Elodea cells able to withstand distilled water without bursting?
Now lift the coverslip and dab off some of the excess water with a paper towel (don’t dry the leaf). Add a drop
of concentrated saline solution (10% NaCl) and replace the coverslip. Observe the Elodea leaf again to look for
plasmolysis.
Make a neat drawing of a few plasmolyzed cells, including all the detail you can see. Label the cell wall, cell
surface membrane, cytoplasm, and a chloroplast. Include an informative title and the magnification.
Did salt (either Na+ or Cl- ) penetrate the cell wall? Refer to your results to justify your answer.
Did salt (either Na+ or Cl- ) penetrate the cell surface membrane? Refer to your results to justify your
answer.
31
32
33
34
Biology 3
Merritt
Name
Period
REVIEW: Using the Compound Microscope
Estimating Object Sizes and Drawing Magnification
Provide the requested information below. Show your calculations on the back of this paper or on a separate
sheet. Identify the object (by letter) associated with each set of calculations.
1. Object Size. Estimate the actual sizes of the objects below.
Field diameters are: 40X = 4500 µm; 100X = 1800 µm; 400X = 450 µm.
View through microscope
A
B
C
D
Object crosses
field 1.6 X
Object crosses
field 1.4 X
Magnification 40X
Object
Size
100X
µm
100X
(L)
µm
(W)
µm
400X
µm
µm
2. Drawing Magnification. Calculate drawing magnifications and add scale bars of the specified lengths to
the drawings below.
Drawing
Drawing
Magnification
Scale bar:
1000 µm
500 µm
1000 µm
200 µm
35
Biology 3
Merritt
Name
Period
REVIEW: Using the Compound Microscope, 2
Estimating Object Sizes and Drawing Magnification
Provide the requested information below. Show your calculations on the back of this paper or on a separate
sheet. Identify the object (by letter) associated with each set of calculations.
1. Object Size. Estimate the actual sizes of the objects below.
Field diameters are: 40X = 5100 μm; 100X = 2000 μm; 400X = 510 μm.
View through microscope
A
Magnification 40X
Object
Size
B
C
D
100X
400X
400X
μm
μm
μm
μm
2. Drawing Magnification. Calculate drawing magnifications and add scale bars of the specified lengths to the
drawings below.
Drawing
Drawing
Magnification
Scale bar:
500 μm
500 μm
250 μm
150 μm
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37
38
Biology 3
Merritt
Name
Period
REVIEW: Membrane Transport
1. Consider the cell to the right. Initially, the solutions inside and outside
the cell are isoosmotic. Explain what will happen under each of the
scenarios listed below. Justify your answer, referring to the transport
processes discussed in lecture.
a. Membrane impermeable to A and B.
b. Membrane permeable to A but not B.
c. Membrane permeable to B but not A.
A
A
B
B
B B
A
B
A
A
A
A
A
A
2. Consider an artificial cell constructed only of a phospholipid bilayer surrounding dH2O. The membrane is
composed entirely of phospholipids. What will happen when this cell is placed in each of the following
solutions? Explain your answer, referring to the transport processes discussed in lecture.
a. 0.3M methanol (CH3OH)
b. saturated N2 solution
c. 0.3M KCl
d. 0.3M sucrose (a disaccharide)
e. dH2O
3. Consider the solutions A–G listed below. What will happen when the artificial cells described in parts a and
b are placed in each solution? Explain your answer, referring to the transport processes discussed in lecture.
A.
B.
C.
D.
0.1M methanol
0.3M methanol
0.5M methanol
0.1M sucrose
E. 0.3M sucrose
F. 0.5M sucrose
G. dH2O
a. An artificial cell surrounded by a membrane composed entirely of phospholipids. Inside the cell is a
0.3M solution of proteins.
b. An artificial cell surrounded by a membrane composed entirely of phospholipids. Inside the cell is a
0.3M solution of methanol.
+
4. An animal cell is transferred to an isoosmotic solution that contains K . The cell remains unchanged. A
different animal cell, also isoosmotic to the solution, expands and explodes when placed in the solution.
Based on this information, what can you infer about the membrane structure of the two cells and the
transport processes that are operating?
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ANIMATIONS: Cells, Membranes, and Membrane Transport
From my home page,
Click Links;
Open Anatomy & Physiology Animations: 1
Animations of Cells:
Click the Cell Structure button
1.
Comparison of Prokaryote, Animal and Plant Cells by Rodney F. Boyer
Interactive tutorial and test program
2. Flash animations of Biological Processes by John L. Giannini
Look under the Cell Structures animations. Good representations of protein synthesis and transport in the
endomembrane system; phagocytosis.
3. Cell Tutorial from "Cells Alive!"
Computer models of animal and plant cells. Place cursor over organelles and click to get more information.
4. Simple cell by Terry Brown
Click on Cell Structure and Function link. Models of plant and animal cells. Place cursor over organelles and click
to get more information.
5. A typical Cell Wisconsin Online
Great computer pictures of animal cell. Tutorial to learn structures.
6. Identifying Eukaryotic Animal Cell Organelles Wisconsin Online
Tour of an animal cell and its organelles.
7. Lysosomes McGraw-Hill
Excellent animation showing how lysosomes are formed and function.
8. Interactive Cell Quiz zeroBio
Like it says, an interactive quiz.
Animations of Membranes and Membrane Transport:
Click the Cell Transport button
1. Membrane Transport Purdue University
Excellent tutorial. Goes into more detail than you need to know about transport channels. *****
2. Membranes McGraw-Hill
Watch Endocytosis and Exocytosis. Ignore receptor-mediated endocytosis.
3. Osmosis by Terry Brown
4.
5.
6.
7.
8.
A simple animation of osmosis.
Interactive Cellular Transport by Rodney F. Boyer
Good animation. Some of the questions are more detailed than required, but you should be able to figure them out.
Osmosis McGraw-Hill Companies, inc
Three problems. Can predict outcomes when moving objects among solutions of different concentrations.
Passive and Active Transport from Northland Community and Technical College
Excellent animations and explanations to differentiate among diffusion, facilitated diffusion, osmosis, active
transport, and endocytosis. *****
Construction of the Cell Membrane Wisconsin Online
Presents membrane structure and components of membranes; then review quiz.
http://www2.nl.edu/jste/transprt.htm
Great text/diagram description of transport across membranes. Not available through AP animations; you’ll have to
key in the web address yourself. *****
Estimating object size, drawing magnification
1. http://www.mun.ca/biology/Help_centre/1001_2_tutorialpages/Measuring_scope.html
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