Major Ways Molecules Move Across Cell Membrane

1
Major Ways Molecules Move Across Cell Membrane

• Name five different ways that molecules can move
  across the cell membrane

2
Cell Membranes and Fluid Balance

• Composition of cell membrane?
• Intracellular vs. interstitial vs. extracellular
  fluid compartments
• Composition of the fluids in these compartments?
• How is composition maintained?
• Osmolarity vs. tonicity

3
Extracellular
Figure taken from http//sorrel.humboldt.edu/jl
g21/Zoo20310/Lab20220ADAM20electrolytes/fluid
20compartments.gif
4
What are the major differences in composition of
the intracellular and extracellular fluid?
Between the interstitial fluid and the plasma?
Figure 5-3b
5

• Simple diffusion
• Characteristics

Figure 5-5
6
Figure 5-6
7
Table 5-1
8
2. Facilitated Diffusion Characteristics
Figure 5-7 (3 of 3)
9
Figure 5-9 - Overview
10
Figure 5-10
11
Figure 5-14
12
Figure 5-15
13
Figure 5-11
14

• Primary Active Transport
• Characteristics

Figure 5-4
15
Table 5-2
16
Figure 5-16
17
Figure 5-17 - Overview
18

• Secondary Active Transport
• Characteristics

19
Figure 5-18 - Overview
20
Figure 5-12 - Overview
21
Table 5-3
22
Figure 5-19
23
The glucose transporters demonstrate common
characteristics of all protein transporters
Table 5-4
24
1. Similarly shaped/charged molecules can
compete for transport
Figure 5-20
25
2. Some similarly shaped molecules can bind, but
when they do, transport is stopped (competitive
inhibition)
Figure 5-21 - Overview
26
3. When the number of transporters is fixed,
increasing the concentration of the transported
molecule will eventually saturate the
transporters, and the rate will remain at its
maximum (unless more transporters are made).
Figure 5-22
27

• Test Your Knowledge
• Steroid hormones pass directly through the cell
  membrane to activate protein production. What
  type of transport is this? Why?
• Why can urea diffuse freely from plasma into
  cells when most cholesterol, although
  lipid-soluble, must cross a membrane by
  receptor-mediated endocytosis?
• From the graph below, what transport method
  appears to be used for the transfer of substance
  Z into a cell? Explain.
• Choose A if the statement refers to active
  transport, B if the statement refers to passive
  transport, and C if it can refer to both.
• Movement of molecules from an area of high
  concentration to an area of low concentration.
• Movement of molecules via proteins embedded in
  the cell membrane, requires ATP.
• Movement of molecules against the concentration
  gradient.
• A co-transporter is involved in molecule
  movement.
• Movement of molecules that requires ATP.
• This tends to create an equilibrium state.

How could you test whether it was primary or
secondary active transport?
28
Receptor mediated endocytosis
Figure 5-24 - Overview
29
Transepithelial transport
Figure 5-25
30
Figure 5-26
31
How do cells maintain their volume? What factors
influence their ability to maintain their volume?
Movement of water toward the area of highest
solute concentration
Osmolarity of the cell and solution surrounding it
Tonicity of the solution outside the cell
32
The solution with the highest solute
concentration has the highest osmotic pressure
Figure 5-29 - Overview
33
Osmolarity total number of dissolved particles
in solution
Osmolarity molar concentration X number of
particles in solution Osmolarity of 2M glucose?
1M NaCl? 1M MgCl2?
Table 5-6
34
Tonicity describes the volume change that occur
if a cell were placed in that solution, after the
cell has come to equilibrium with the solution.
Tonicity is not measured in units, it is only a
comparative term.
Can osmolarity tell you whether a solution is
hypo-, iso-, or hyper-tonic?
Table 5-7
35
Figure 5-30a
36
Figure 5-30b
37
Figure 5-31a
38
Figure 5-31b
39
Figure 5-31c
40
Figure 5-31d
41
Table 5-8
42
Table 5-9
43

• Test Your Knowledge
• Which of the following solutions have the most
  water per unit volume
• 1 M glucose, 1 M NaCl, or 1OsM NaCl ? How do you
  know?
• Two compartments are separated aby a membrane
  that is permeable to water and urea but not to
  NaCl. Which way will water move when the
  following solutions are placed in the two
  compartments?
• Compartment A Membrane Compartment B
• 1 M NaCl 1 OsM NaCl
• 1 M urea 2M urea
• 1 OsM NaCl 1 OsM urea
• You have a patient who lost 1 liter of blood, and
  you need to restore volume quickly while waiting
  for a blood transfusion to arrive from the blood
  bank.
• Which would be better to administer 5 dextrose
  in water or 0.9 NaCl in water? Defend your
  choice.
• How much of your solution of choice would you
  have to administer to return blood volume to
  normal?

44
Resting Membrane Potential The relative charge
difference (electrical gradient) between the
intracellular and extracellular
compartments. What can influence the charges on
the inside or outside of the cell?

• Charge-charge interactions

• Activity of active transport pumps

• Relative concentration of each ion

45
Figure 5-32 - Overview
46
Figure 5-33
47
Figure 5-34a
48
Figure 5-34b
49
Figure 5-34c
50
Figure 5-35
51
Figure 5-36
52
Figure 5-37