1. CHAPTER 3 … 3.1 THE CELL MEMBRANE …
A. Transport Across The Cell Membrane
Semipermeable
Nonpolar substances, small
Polar + charged substances

2. Solutions and Transport
Solvent =
solutes =
Intracellular fluid—fluid ______ cells
Interstitial fluid—fluid ________ of cells
Waste
and
Signals
Nutrients
and
Signals

3. 3.1 THE CELL MEMBRANE … Types of Transport Passive Active
A. Transport Across The Cell Membrane …
Types of Transport
Passive
Active

4. 1. Passive Processes = Diffusion & Filtration
a) Diffusion =
Equilibrium
kinetic energy
Concentration Gradient
Types:
(a) Simple diffusion
directly through the
phospholipid bilayer

5. Dialysis: simple diffusion of solutes through a membrane
i) Simple Diffusion …
i) Simple Diffusion =
Dialysis: simple diffusion of solutes through a membrane
Simple Diffusion of Gases– O2 and CO2

6. Diffusion … ii) Facilitated Diffusion =
Needs Proteins
Carrier Proteins
Specificusually polar molecule
Channel Proteins
- general, usually ions
(b) Carrier-mediated facilitated
diffusion via protein carrier
specific for one chemical; binding
of substrate causes shape change
in transport protein
(c) Channel-mediated facilitated
diffusion through a channel
protein; mostly ions selected
on basis of size and charge

7. iii) MOVEMENT OF WATER via Diffusion
= OSMOSIS when is through a membrane
Two Ways:
Simple Diffusion
Facilitated Diffusion
Figure 3.10d

8. iii) MOVEMENT OF WATER via Diffusion …
If solute concen. differs, and solute cannot move through: then water will ____________
IMPORTANCE: Intracellular and Intercellular fluids must ____________________________

9. If solute can move through

10. Tonicity – how the solute concen
Tonicity – how the solute concen. affects water movement and cell volume
Isotonic –
Hypertonic –
Hypotonic –
Example: Where will
BLOOD CELL: the water go?
98% water
2% solutes
SOLUTION:
5% solute
___ water

11. Applications of Tonicity
Cell placed into isotonic solution
Cell placed into hypertonic solution
Cell placed into hypotonic solution

12. REVIEW: Diffusion Through the Plasma Membrane
Extracellular fluid
Small lipid-
insoluble
solutes
Lipid-
soluble
solutes
Lipid-insoluble
solutes
Water
molecules
Lipid
bilayer
Cytoplasm
(a) Simple diffusion
(b) Carrier-mediated facilitated
diffusion
(c) Channel-mediated
facilitated diffusion
(d) Osmosis,
Figure 3.7

13. Passive Processes … b) Filtration
Passage of water and solutes through membrane by a force
Gravity
Hydrostatic Pressure
Pressure gradient
Size of pores in membrane
Large biochemicals do not go through

14. 2. Active Processes – Energy
Substances transported :
Size
Lipid Solubility
Concentration Gradient

15. 2. Active Processes … OVERVIEW: Two types of Active Processes:
Active transport
Primary Active Transport
Secondary Active Transport
Vesicular transport
Endocytosis
Phagocytosis
Pinocytosis
Receptor-Mediated Endocytosis
Exocytosis

16. a) Primary Active Transport
Pumps: proteins that use ATP to transport molecules against concen. gradient
Na-K pump (Na-K ATPase)
Maintains Electrical Gradient
One or two substances can be moved K+
Na+
Extracellular fluid
Na+ P
Na+ P
Na+
Na+ K+ K+
Na+ P
Cytoplasm K+
ATP
ADP
Figure 3.11

17. Sodium/Potassium Pump
Cytoplasm
Extracellular fluid
Cell
Concentration gradients
of K+ and Na+
Na+ K+
Figure 3.10

18. Binding of cytoplasmic Na+ to the pump protein
Extracellular fluid
Cell
ADP
Concentration gradients
of K+ and Na+
Binding of cytoplasmic
Na+ to the pump protein
Na+ K+
ATP P
Figure 3.10

19. Use of ATP causes the protein to change its shape. Figure 3.10
Cytoplasm
Extracellular fluid
Cell
ADP
Concentration gradients
of K+ and Na+
Binding of cytoplasmic
Na+ to the pump protein
Na+ K+
ATP P
Use of ATP
causes the
protein to
change its shape.
Figure 3.10

20. The shape change expels Na+ to the outside. Figure 3.10
Cytoplasm
Extracellular fluid
Cell
ADP
Concentration gradients
of K+ and Na+
The shape change
expels Na+ to the
outside.
Binding of cytoplasmic
Na+ to the pump protein .
Na+ K+
ATP P
Use of ATP causes the
protein to
change its shape.
Figure 3.10

21. Figure 3.10 Extracellular fluid Binding of cytoplasmic
ADP
Concentration gradients
of K+ and Na+
The shape change
expels Na+ to the
outside.
K+ binding
Binding of cytoplasmic
Na+ to the pump protein.
Na+ K+
ATP P Pi
Use of ATP
causes the
protein to
change its shape.
Figure 3.10

22. Original conformation of the pump protein is restored
Cytoplasm
Extracellular fluid
Cell
ADP
Concentration gradients
of K+ and Na+
The shape change
expels Na+ to the
outside.
K+ binding
Binding of cytoplasmic
Na+ to the pump protein
Na+ K+
ATP P Pi
Use of ATP
causes the
protein to
change its shape.
Original conformation of the
pump protein is restored
Figure 3.10

23. Original conformation of the pump protein is restored
Cytoplasm
Extracellular fluid
K+ is released ; the
cycle repeats.
Cell
ADP
Use of ATP
causes the
protein to
change its shape.
Concentration gradients
of K+ and Na+
The shape change
expels Na+ to the
outside.
Original conformation of the
pump protein is restored
K+ binding
Binding of cytoplasmic
Na+ to the pump protein .
Na+ K+
ATP P Pi
Figure 3.10

24. Solute Pumps cont.
Symport system –
Antiport system –

25. b) Active Transport– Secondary
Stored energy from primary active transport creates a concentration gradient for an ion (usually Na)
When the ion diffuses the released energy is used to transport another solute
The concentration gradient for the ion is usually created by the Na-K Pump
SEE NEXT SLIDE
Extracellular fluid
Glucose
Na+-glucose
symport transporter
releasing glucose
into the cytoplasm
Cytoplasm 2
Example: Na+ diffuses across the
membrane and moves glucose
against its concentration gradient
into the cell.

26. Types of Pumps 1) Symport system – 2) Antiport system –
Extracellular fluid
Types of Pumps
1) Symport system –
2) Antiport system –
Example: Symport system that transports glucose into cells of the small intestine using the energy from Na+ diffusion into the cell.
Example: Antiport system that that transports H+ out of the cell using the energy from Na+ diffusion into the cell
Na+-K+
pump
Cytoplasm 1
The ATP-driven Na+-K+ pump
stores energy by creating a
steep concentration gradient for
Na+.
Then, the subsequent diffusion of Na releases energy.
Figure 3.11 step 1

27. Example: transport of glucose
Extracellular fluid
Glucose
Na+-glucose
symport
transporter
loading
glucose from
ECF
Na+-glucose
symport transporter
releasing glucose
into the cytoplasm
Na+-K+
pump
Cytoplasm 1
The ATP-driven Na+-K+ pump
stores energy by creating a
steep concentration gradient. 2
Na+ diffuses back across the
membrane and moves glucose
against its concentration gradient
into the cell.
Figure 3.11 step 2

28. Active Processes … c) Vesicular Transport
= Transport of large particles and macromolecules via vesicles
needs ATP
3 Major Types:
Endocytosis
Receptor-mediated
Exocytosis
Figure 3.12bkE

29. i. Endocytosis
Phagocytosis—cell membrane extends around solids. --Vesicle then:
- Example: White Blood Cells engulfing microbes
Vesicle
Figure 3.13a

30. (2) Pinocytosis Plasma membrane in-folds.
- Example: Nutrient absorption in the small intestine .
Vesicle
Figure 3.13b

31. (ii) Receptor-Mediated Endocytosis
Vesicle has Receptors for specific substances (ligands).
Ligand = any substance that attaches to a receptor protein in the cell membrane.
- Examples: Uptake of iron and insulin
Substance
Receptor
Vesicle
Figure 3.13c

32. iii) Exocytosis
Vesicle fuses with cell membrane and substance is released. Vesicle membrane then becomes part of cell membrane.
The process of exocytosis
Extracellular
fluid
Fusion pore formed
Secretory
vesicle
The membrane-
bound vesicle
migrates to the
plasma membrane. 1
The vesicle
and plasma
membrane fuse
and a pore
opens up. 3
Molecule to
be secreted
Cytoplasm
There, proteins
at the vesicle
surface bind to proteins in plasma membrane . 2
Vesicle
contents are
released to the
cell exterior. 4
Figure 3.14a

33. Neurotransmitter release Mucus Secretion
Exocytosis …
Examples
Hormone Secretion
Neurotransmitter release
Mucus Secretion
Figure 3.12b

34. END
SPARE SLIDES FOLLOW:

35. Review Question
Aside from ______________ which requires hydraulic pressure gradients, all other forms of _____________ transport are driven by _____________, the movement of molecules down their concentration gradients.

36. Review Question 5. Which of the following require ATP?
Facilitated diffusion
Osmosis
Endocytosis
Solute pumping
Simple diffusion
Pinocytosis
Exocytosis

37. Review Question
3. Membrane potential is predominantly controlled by what type of ions? What 2 types of cells are particularly sensitive to disturbances of the RMP?

38. Review Questions
4a. Specialized glycoproteins that anchor cells to the extracellular matrix and help attract defensive cells after tissue damage are known as ________ _________ ___________. 4b. ___________ ___________ bind with _________ (hormones, neurotransmitters and other signal molecules) to promote cell recognition, activate membrane bound enzymes, open gated chemical and ion channels, and stimulate second messenger signal transduction among others.