_________-r
Name:
Date:
The Cell
Membrane
G
Cell Exterior
E
A
A
F
B
D
(*Color the WHOLE picture!!! Do NOT just color one example!)
The Cell Membrane:
A.
B.
C.
D.
E.
F.
G.
Phospholipid Bilayer.
Hydrophilic Head
Hydrophobic Tail
Cholesterol Molecule
Integral Proteins
Alpha Helix Proteins
Carbohydrates
............
...........
brown (just the arrow>
yellow (both pictures)
orange (both pictures)
purple
blue
red
green
The Cell Membrane
(Sec 6.2)
1. Define the cell (plasma) membrane:
2. What does the term semi-permeable mean?
3. What would be some examples of materials that would be able to pass through
something semi-permeable? What would not be able to pass?
4. What two organic compounds are the cell membrane mostly composed of?
5. What does hydrophobic and hydrophilic mean?
6. Due to the make up of the cell membrane, how many layers are there?
7. Due to the fact in #6, the membrane is often referred to as a
8.
are the organic substances embedded in the membrane.
9, What do these organic compounds do for the cell membrane?
10. The space below is reserved for an explanation about the structure of the
membrane that will be given later from your teacher.
_________
Date
Name
Chapter Assessnent
Cellular Transport
.As;
Thinking Critically
animal cell.
The graph shows typical concentrations of several ions inside and outside an
graph to answer
Concentrations of ions inside the cell are shown in gray, outside in black. Use the
questions 1—5.
CA2
1
4
Mg2
HCO
Cl-
I
0
50
I
100
I
150
Concentration (mM)
tration of
1. Compared to its surroundings, does an animal cell contain a higher or lower concen
potassium (IQ) ions?
2. Which ions are in the greatest concentration outside the animal cell?
3. Which ions are in the lowest concentration inside the animal cell?
4. What is the approximate concentration, in m?VI, of Mg ions inside the cell?
remain?
5. If all available Na and—C1 ions combine to form NaC1, do any excess Na or C1 ions
If so, which?
Answer the following question.
t in many organisms, including plants, algae, fungi and some prokaryotes. Cell
6. Cell walls are presen
cellulose. This fibrous
walls lie outside the cell membrane and are composed of carbohydrates called
les to enter. If this is the case,
structure is very porous and unlike the cell membrane allows any molecu
back to O.Chem and look up
what does the cell wall provide for the cells of these organisms? [Hint: go
what cellulose is and does.]
4
F
A View of the Cell
Applying Scientific Methods
In the 1 890s, E. Overton performed experiments to determine the structure of the plasma membrane.
After many years and various procedures, he determined that large, uncharged molecules enter a cell at
a rate proportional to their solubility in lipids. This observation was the first indication that the plasma
membrane is probably made up of lipids. Many scientists began to pursue the question of how the lipids
were arranged.
In 1925, two Dutch scientists determined that the area covered by the lipids from a single red blood
cell is twice the area of the surface of the cell. From this, they reasoned that the cell is covered by a double
layer of lipid molecules. Based on this work, various scientists hypothesized that the membrane was like a
“fat sandwich” with two outer layers of protein on the surface of the lipid layer.
None of the ideas seemed a satisfactory explanation until microscopic studies of membranes prepared
by a new technique of “freeze-fracture” revealed that the proteins are actually embedded in the lipid layer.
In 1972, on the basis of these results and other evidence, two American scientists proposed the fluidmosaic model.
7. What was the problem that Overton was trying to solve with his experiments?
8. Is his hypothesis stated in the discussion above? If so, what was it?
9.. The result of one experiment often leads to further experiments.How do Overton’s experiments
illustrate this fact?
-
10. What conclusion did the Dutch scientists reach?
11. What inference did the Dutch scientists make to reach their conclusion?
12. What model of the plasma membrane was based on their results?
13. Why was it almost 50 years between the Dutch scientists’ research and the proposal of a fluid
mosaic model?