1. Anatomy & physiology of cells
Huan Ma（马欢），PhD
Department of Physiology
Room 515, Block C, Research Building
School of Medicine, Zijingang Campus
Tel:

2. ahmad ata

3. Structure of cell membrane:
Fluid Mosaic Model (Singer & Nicholson, 1972)

4. Net flux accounts for solute movements in both directions.
Note: the partition between the two
compartments is a membrane that
allows this solute to move through it.
Net flux accounts for solute
movements in both directions.

5. Simple Diffusion 单纯扩散 Relative to the concentration gradient
movement is DOWN the concentration gradient ONLY (higher concentration to lower concentration)
Rate of diffusion depends on
The concentration gradient
Charge on the molecule
Size
Lipid solubility
Temperature

6. In simple diffusion,
flux rate is limited
only by the
concentration
gradient.
In carrier-
mediated
transport,
the number
of available
carriers
places an
upper limit
on the
flux rate.

7. Characteristics of ion channels
Specificity
Gating

8. Three types of passive, non-coupled transport through integral membrane proteins

10. facilitated diffusion, solutes move in the direction predicted
membrane
In both simple and
facilitated diffusion,
solutes move in the
direction predicted
by the concentration
gradient.
In active transport, solutes move opposite to the
direction predicted by the concentration gradient.

11. Active transport 主动转运 Primary active transport 原发性主动转运
Secondary active transport 继发性主动转运

12. Primary Active Transport
making direct use of energy derived from ATP to transport the ions across the cell membrane

13. The transported solute binds to the protein
as it is phosphorylated (ATP expense).

15. Extracelluar (mmol/L) Intracellular (mmol/L)
Concentration gradient of Na+ and K+
Extracelluar (mmol/L) Intracellular (mmol/L) Na K

16. Here, in the operation of the Na+-K+-ATPase, also known
as the “sodium pump,” each ATP hydrolysis moves three
sodium ions out of, and two potassium ions into, the cell.

17. Na+-K+ pump (Na+ pump, Na+-K+ ATPase)
electrogenic pump

18. Physiological role of Na+-K+ pump
Maintaining the Na+ and K+ gradients across the cell membrane
Partly responsible for establishing a negative electrical potential inside the cell
Controlling cell volume
Providing energy for secondary active transport

19. Other primary active transport
Primary active transport of calcium
Primary active transport of hydrogen ions
etc.

20. Secondary Active Transport
The ion gradients established by primary active transport permits the transport of other substances against their concentration gradients

21. Secondary active transport uses the energy in
an ion gradient to move a second solute.

22. Cotransport Countertransport
the ion and the second solute cross the membrane in the same direction
(e.g. Na+-glucose, Na+-amino acid cotransport)
Countertransport
the ion and the second solute move in
opposite directions
(e.g. Na+-Ca2+, Na+-H+ exchange)

23. Cotransporters

24. Exchangers

25. Ion gradients, channels, and transporters in a typical cell

28. Solvent + Solute = Solution
Osmosis（渗透）
Solvent + Solute = Solution
Here, water is the solvent. The addition of solute lowers the water concentration. Addition of more solute would increase the solute concentration and further reduce the water concentration.

29. Begin:
The partition between
the compartments
is permeable to water
and to the solute.
After diffusional
equilibrium has occurred: Movement of water and solutes has equalized solute and water concentrations on both sides of the partition.

30. Begin:
The partition between
the compartments
is permeable to water only.
After diffusional
equilibrium has occurred:
Movement of water only
has equalized solute
concentration.

32. Role of Na-K pump in maintaining cell volume

33. Response to cell shrinking

34. Response to cell swelling

35. Endocytosis and Exocytosis 入胞与出胞

36. Alternative functions
of endocytosis:
Transcellular transport
2. Endosomal processing
3. Recycling the membrane
4. Destroying engulfed materials

37. Endocytosis

38. Exocytosis

39. Two pathways of exocytosis
Constitutive exocytosis pathway -- Many soluble proteins are continually secreted from the cell by the constitutive secretory pathway
Regulated exocytosis pathway -- Selected proteins in the trans Golgi network are diverted into secretory vesicles, where the proteins are concentrated and stored until an extracellular signal stimulates their secretion

40. Epithelial Transport

43. Glands

44. Summary Diffusion: solute moves down its concentration gradient:
simple diffusion:
small (e.g., oxygen, carbon dioxide)
lipid soluble (e.g., steroids)
facilitated diffusion:
requires transporter (e.g., glucose)

45. Active transport: solute moves against its concentration gradient:
primary active transport:
ATP directly consumed (e.g., Na+ -K+ ATPase)
secondary active transport:
energy of ion gradient (usually Na+) used to move second solute (e.g., nutrient absorption in gut)
Exo- and endo- cytosis:
large scale movements of molecules