Cell Membranes
Separating Dead from Alive
Identify the radical below.
57%
Amine
Hydroxyl
Carboxyl
Monosaccharide
24%
19%
ch
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M
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C
H
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yl
m
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0%
A
1.
2.
3.
4.
Identify the molecule shown.
Butene
Propene
Propane
Butane
None of the above are a
good response.
62%
33%
0% 0%
e
e
N
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ar
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e
ab
ov
of
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P
B
ut
an
an
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p
en
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P
ut
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5%
B
1.
2.
3.
4.
5.
What is the function of the molecule shown below?
50%
40%
C
om
po
ul
a
eg
R
el
Fu
to
ry
so
ur
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to
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5% 5%
er
gy
3.
4.
Energy storage
Component of cell
membrane
Fuel source
Regulatory
En
1.
2.
I. Functions
Living part of the cell-legitimate cell organelle
Separates living from the nonliving world
Semipermeable-regulates what enters and exits the cell
Partitions the cell into different regions where different
functions take place
Participates in chemical reactions
Transmits signals between outside of cell and the
cytoplasm[
II. Cell membrane characteristics
•
•
•
•
A.
B.
C.
D.
Semipermeable
Elastic
Wettable
Very thin-around 10 um
II. Early model
• A. Davison Danielli
Model
1. mainly lipid
2. aqueous
channels
3. surface protein
4. weaknesses
Phospholipids interacting in wateramphipathic
RBC cell membrane-clearly
resembles Davson-Danielli model
III. Fluid mosaic model
• A. Main
ingredients
• Phospholipids
• Proteins both
intrinsic and
extrinsic
• Cholesterol
• Glycocalyx
Your textbook’s Diagram
B. Protein functions
What do you think the function of this membrane protein
might be?
1. Transport
2. Cell to cell adhesion
3. Cell to cell
recognition
4. Energy production
Electron micrograph of cell
membrane
• http://www.med.uiuc.edu/histo/large/atlas/i
mage/temgi3/75000a1.htm
C. Chemical properties of membrane
• 1. Lateral fluidity
• 2. Two dimensional
fluidity-rapid
movement of lipids
and proteins
• 3. Flexible
• 4. Self sealing
• 5. Can fuse
C. Chemical properties of membrane
6. Effect of saturated
vs. unsaturated
7. Role of cholesterol
IV. Function of Cell MembranePassive Transport
A. Diffusion
1. definition
2. example
3. across cell
membrane
Your textbook’s figure of diffusion
IV. Function of Cell MembranePassive Transport
• B. Facilitated
Diffusion
1. mediated by
intrinsic protein
2. diffusion gradientno ATP
3. glucose entrance
into cell
4. boy scout analogy
C. Osmosis
•
•
•
•
•
•
1.
2.
3.
4.
5.
6.
Definition
U-tube
Explanation
Common examples
Terms of tonicity
Turgor pressure
In which direction will water move?
1. A => B and B
rises
2. B => A and A rises
3. A  B and the
sides stay at the
same level
4. No idea
Your textbook’s figure of osmosis
(a)
Plasma
membrane
(b)
Nucleus
(c)
Vacuole
Vacuole
Vacuolar
membrane
(tonoplast)
Cytoplasm
Plasma
membrane
Figur
V. Function of cell membrane-active
transport
• A. Definition
• B. Endocytosis
– 1. Phagocytosis
Phagocytic vesicles
2. Pinocytosis
Microvilli
Pinocytotic vesicle
Cytosol
Figur
3. Receptor mediated pinocytosis
(b)
0.25µm
Figur
C. Exocytosis
D.
Membrane Pumps
1. Materials are moved against concentration
gradient
2. An integral protein molecule is involved
3. ATP is necessary
4. Sometimes membrane potentials are produced
5. Na ion-K ion pump is an example
ATP
ADP
2. A phosphate group is
transferred from ATP to
the transport protein
3. The transport protein undergoes a conformational
change, releasing three
sodium ions outside the cell.
1. Three sodium ions bind
to the transport protein
(b)
4. Two potassium ions bind
to the transport protein
6. The transport protein
5. The phosphate is released
returns to its original shape:
Two potassium ions are
released inside the cell
Figur