The document is a set of lecture notes from Addis Ababa University focusing on cell physiology and transportation, aimed at medical students. It covers objectives like understanding cell structures, membrane proteins, and cell transport mechanisms, including passive and active transport. Key components discussed include the human cell structure, the fluid mosaic model of membranes, types of membrane transport, osmosis, osmotic pressure, and active transport mechanisms.

1. Addis Ababa University
School of Medicine
Department of Medical Physiology
Lecture Notes
on
Cell Physiology and transportation
for
PC I Medical students
1

2. Objectives
• At the end:
– Able to discus the structures of the a cell
– Able to discuses the functions of the structures of a cell
– Able to list the types and functions of membrane proteins
– Able to discus cell transport
– Able to discuses about body fluid
2

3. Cell Physiology
• The human body composed of non-cellular and cellular components
• Non-cellular components
– Water
– Macro -nutrients: carbohydrate, protein, lipid, nucleic acid
– Micro- nutrients: vitamins, electrolytes
• Cells:
 Smallest structural & functional unit of life
 Small in size  10-20um
 Large in number  75-100 trillion
 Arranged in d/f functional structures
3

4. Structural or functional classification
4
Fig1: Cell types

5. Fundamental theories and cell types
 Types
 Eukaryotic
 Blood, nerve, muscle, fat and glandular cells
 Prokaryotic cells
 Bacteria, virus
 Have many functions
 Transportation, Defenses, protection
5

6. Structures of the human cells
1) Plasma/cell membrane
– Double, thin, flexible (fluid mosaic model) structure surrounding animal cell
– Composed of biological macromolecules
• Carbohydrates, proteins, lipids and cholesterol
– Functions:
• Selective barrier (semi-permeable) and transport
• Support, protect the cell & retain cytoplasmic contents
• Recognition (identity proteins)
– Pattern recognition receptors
» Detect molecules on pathogens
• Maintains chemical & electrical gradients
• Communication
• Controls and directs cellular activities
6

7. Major compositions of cell membrane
• Phospholipids (25%)
• Form double membrane, lipid bilayer (outer and inner)
– Asymmetry ( variation in composition and arrangement)
– Amphipathic molecule
» Hydrophilic and hydrophobic properties
• Carbohydrates(3%)
– Combined (glycoprotein and glycolipid): recognition and blood clotting
• E.g Glycocalyx ( blood clotting)
• Proteins (55%): membrane proteins
– Intrinsic and extrinsic
• Cholesterol (13%)
– For immobilization of lipid molecules and give extra support
7

8. Fluid mosaic model of cell membrane
8
The mosaic model states that a membrane is a fluid structure
with a “mosaic” of various proteins embedded in it.
Fibers (collagen) where
cell rest is called basal
lamina
Fig 2: Fluid mosaic model

9. Membrane proteins
i- Integral proteins
– Transmembrane, intrinsic proteins
– Strongly bonded with lipid bilayer
– Not removed easily with out affecting the membrane
– Most of them are glycoproteins
• Receptors (GPCR)
• Ion channels
• Carriers (permease, pumps)
9

10. ii- Peripheral proteins
– Attached to the inner membrane
– Not penetrate the hydrophobic core of the membrane
– Easily removed
– Enzymes
• Protein kinases, Phospholipases
– Important
• Cell signaling
• Anchoring (integral proteins and cytoskeleton)
10
Membrane proteins con’t

11. Membrane proteins con’t
11
Fig 3: Integral and peripheral membrane proteins

12. Functions of membrane proteins: summary
• Receive chemicals and transport substances
– Receptor and transporter proteins
– Transporters proteins (uniport, symport and antiport)
• Link structures: Linkers proteins
• Communication(gap junctions) and recognition (identity)
– Immune cells can recognize self cells
• Enzymatic reaction and signal transduction
• Cell adhesion: one cell to an other
– Platelet attached on endothelial cells
• Connect the cell with the cytoskeleton
• Keeping the integrity of membrane: structural proteins
12

13. Membrane proteins and their functions con’t
13
Fig 4: Functions of membrane proteins

14. Parts of human cell...
2) Cytoplasm
– Space b/n the nucleus and cell membrane
– Contains fluid: cytosol/ICF with d/f compositions and
Suspended structures : organelles (except red cells)
• The machinery of the cells
• Has their own functions
14
Cytoplasm
cytosol
Water, glucose,
proteins, electrolytes
Dispersed
particles
Smaller: FA
Larger: neutral fat,
glycoprotein, excretory
granules
Organels
Some cells lack organelles ( RBCs)

15. Red blood cells
• Lack most of the organelles
– Nucleus (DNA)
• No cellular division and protein synthesis
– Mitochondria
– No ATP production in oxidative phosphorylation
• Glycolysis source of energy
– One glucose molecule  2ATP
15

16. Organelles
• Nucleus
– Largest organelle at the center of the cell
– Has nuclear membrane with nuclear envelop
– Controls the cell functions
• The genes
• Genes: molecules on the DNA that carry and express traits
• Each gene has its own triplet code word
– The functional unit of gene
Gene Gene I Gene II Gene III
code word with sequence CAG AGC GAC
Specific proteins (hormones,
enzymes,activitors, inhibitors)
Protein type I Protein type II Protein type III
16

17. DNA structure
Fig 5: DNA structure(
alpha double helix of two
polynucleotide strands).
17

18. Ribosomes and Endoplasmic reticulum
18
Free
Exocytosis
(active)
sER
 store Ca++(SR in muscle cells)
Steroids
Glycogen phosphatase
Glucokinase
Phosphoglucomutase
phospholipids
GA
 More in
secretary cells
(plasma B cells
and acinar cells )
Fig
6:
Ribosmomes
and
ER

19. Mitochondria and ATP production
19
Fig 7: Mitochondrion
38 ATP’s from one glucose
molecule but 2ATP used for
preparation steps
Nicotinamide
adenine
dinucleotide
(NAD):
NADH
is
the
reduced
form
of
NAD
and
carry
energy
2NADH
2

20. Lysosome …
20
Fig 8: Actions of lysosome
phagosome
Intracellular digestive
system: stomach of
the cell
Suicide
Acid hydrolic enzyme (pH<7)
cytosol pH =7.2

21. Secretory vessicels
• Similar structure with lysosomes
• Contain enzymes not used in the cell, released out
• Glandular cells have secretory vesicles
– Pancreatic gland
– Salivary gland
– Other endocrine gland
21

22. Peroxisomes ( from ER) and action of catalase
22
harmless
Harmless
Fig 9: Action of catalase and peroxidase
Fe losses O2
Oxidized
: Facilitate the formation of H2O2
Peroxisomes
 Replicated from ER
 Release catalase
 Shorter and smoother
Oxidation: 02 gaining and reduction loss of O2. iron reduced 02 this is b/se CO receive
oxygen Thus
CO : reducing agent as it facilitates Fe to loss O2
Fe: oxidizing agent as it facilities CO to gain 02 and oxidized
Oxidized substrate: reducing agent
Reduced substrate: oxidizing agent

23. Cell junctions and types
23
Sheet epithelial cells, BBB
Fig 10: Cells communication
provide strong mechanical
attachments between adjacent
cells.
Electrical signal conducted
1
2
3
4

24. Transport across the cell membrane
24

25. Membrane transport
 Passage of substances across the cell membrane
 Into the cell: influx and Out the cell: efflux
 The passage can be through:
 Lipidbilayer
 Proteins
 Cells differ in their permeability: Variation in :
– Composition and arrangement
25

26. Transport across the cell membrane
26
-Nutrients
-Ions and
Water are
through
-
With out proteins
 Gas
Lipid soluble substances
Alcohol
Protein
Fig 11: Transportation across the cell membrane

27. Types of membrane transport
• Passive transport
– No energy required
• Movement down concentration gradient
• The forces are concentration & electrical gradients
• Substances follow their concentration gradient
– Concentration gradient reduced /eliminated
– Filtration , simple or carrier mediated diffusion and osmosis
27

28. Types of the passive transport...
1 - Simple diffusion
– Through lipid bilayer or leaky channels- not gated ion channels
– Lipid soluble, gas and alcohol (via lipid bilayer)
• Vitamin A, D, E and K
– Lipid insoluble ( via water filled channels)
• Ions , water
– No interaction b/n channel and transported substance
28

29. Transport across the cell membrane
29
Fig 12: Types of Transport

30. Properties of channels
- Water field proteins
- Mostly, allow substances to move down (passive channels- leaky ion
channels)
- Dissipate potential difference
- Opened and closed by gate (gated channels)
- Active channels
- Prolonged activation desensitizes the channels
- Select influx and efflux substances
- Connected with receptors
- E.g ion channels
- Important for excitable cells
30

31. Gated Ion channels con’t
31
 Voltage gated ( charge difference sensors)
Ligand or Chemical gated (Ach, GABA, glutamate)
Light gated (photo sensitive channels)
Mechanical gated ( stretched sensitive channels)

32. Bases of selectivity
 Channels are specific and selective
 The selection is based on
 Size (size of Na+ channel: 0.3 x 0.5 nm)
 The bond nature of the proteins
The charge
 Hydration/unhydration of ions
 Na+ channel (-ve Q) allows unhydrated sodium to pass
 But hydrated potassium still pass through its channel
 The selectivity is less than the carriers
 Not have binding site
32
Unhydrated ion
Hydrated ion
ion
ion
H20

33. Factors affecting the diffusion rate: rate of transport
• Cell membrane thickness
• Molecular Size
• Temperature
• The gradient (electrical and concentration: opposite forces)
– Net influx, F = kpA(C0-Ci)
– The net efflux, F= kpA(Ci-C0)
• kp(Permeability constant)
• The lipid solubility
• Membrane surface area
• Permeability
33
1 2

34. Passive transport…
2- Facilitated diffusion
– It is carrier (permease ) mediated
– Solute binds to the carrier (conformational changes)
• Rotate, open
– The substance is released into the low concentration side
– Substances attached from high concentration region
34

35. Facilitated diffusion…
35
The unique feature of
facilitated diffusion
1. Specificity
2. Competition
3. Inhibition
4. Saturation
5. Transport maximum
Fig 13: Facilitated diffusion

36. Facilitated Diffusion…
– Differ from simple diffusion mainly
• Transport maximum(Vmax) achieved
– Diffusion rate elevated until transport maximum
– Proteins are saturated
– Diffusion rate constant after V max
36
Fig 14: Transport maximum(v max )
Rate of transportation increased as
the concentration of the substance
getting high

37. Passive transport: osmosis and osmotic pressure
3- Osmosis
– Net movement of water from
• The region of high water molecules to low water molecules
• Low solute to the high solute concentration
• Hypotonic to hypertonic solution
– Equalizes water concentration across the membrane
– This movement is there if there is
• Water and solute concentration difference
37

38. Solution tonicity
• Tonicity
 The osmotic activity of body fluid
 Ability of a solution affecting cell volume
 The solution:
 Isotonic, hypotonic and hypertonic against cytosol
 Affects the osmotic pressure of the solution
38

39. A cell in different solution
Solution concentration
compared with concentration
of intracellular fluid
What will be the cell volume if
you add different solution into
the ECF?
 isotonic solution
Hypertonic solution
Hypotonic solution
Fig 15: a cell in different solutions

40. Osmol, osmolarity, osmolality
• Osmol
– Number of osmotically active particles of solute in a solution
• Osmolarity: solute pr kg of solution and is the concentration of
the solution with the unit of mOsmol/L of solution
– The total osmolarity of the body is 280mOsm/L of solution
– And one milliossmole has an osmotic pressure of 19.3mmHg
• Osmolality: solute per kg of water
40

41. Atomic and molecular weight
Atomic weight of elements Molecular weight of compound
Table 1: atomic and molecular weight
41

42. Osmosis and osmotic pressure
• Osmotic pressure
– Force applied by solution to oppose the net movement of water
– Affected by osmole and the tonicity of solution :
• One mole of glucose= 1 osmole/L
• One mole of NaCl = 2 osmole/L
• One mole of HCl = 2 osmole/ L
• One mole of Na2SO4 = 3 osmole/L
– The more the osmotic pressure
• The less movement of water into other compartment
– Size of the molecule in the solution not affect osmotic pressure
• One mole of glucose (C6h12O6) ?
• One mole of NaCl?
42

43. Osmosis and osmotic pressure...
• Determination of osmotic pressure of a solution
– Osmolarity (mOsmol/L) = concentration x number of
dissociable particules
– E.g a 150 mmol/L (conc) solution of NaCl has an
osmolarity of 300 mOsm/L
– Then the osmotic pressure = 5,795mmHg
43

44. Relation between osmol and osmotic pressure
• A solution with 1 miliosmol/L opposes the net movement of water
by 19.3mmHg force
– The osmolarity of the body fluid is 280-300miliosmol/L
– Then the calculated body fluid osmotic pressure= 19.3 x 300 =
5790mmHg
– But the actual total body fluid osmotic pressure is 5500mmHg
(contributed by ions, proteins….)
– The reduction is due to some ions attract to each other like Na+
and Cl- in that their full osmotic effect is reduced
44

45. Molarity and osmotic pressure of a solution
• Calculate the osmolarity and the osmotic pressure of a solution of 0.9% NaCl
• Assume the membrane is impermeable to other solutes
– 0.9% NaCl solution means the solution contains 0.9gm of NaCl in 100ml of the solution
or 9gm/L
 Osmolarity = concentration x osmol
 (9gm/L)/(58.5 gm/mole)= 0.1538mole/L, then for two osmole = 2x
0.1538mole/L = 0.308 osmole/L
 Osmotic pressure
 1mosmle , the osmotic pressure required is 19.3 mmHg
 Then for 0.308 osmole/L = 308mosmole/L = 308 mosmole/L X 19.3 mmHg = 5,
944.4mmHg
45

46. Determination of fluid shift and osmolarities
of a solutions after an other solution infused
• Assume : 2L of hypertonic solution with 3.0% of NaCl infused
into ECF of a 70kg patient whose initial plasma osmolarity is
280mosmole/L. Then determine
– Osmolarity of body after infusion
– Intra and extracellular fluid volumes
46

47. Steep one: Determine the initial conditions before
solution given
47
Table 2: Initial condition of subject

48. • 3.0% Nacl solution means , solution contain 3mg of NaCl in 100ml
or 30gm/L
• Osmol/conc= 30gm/L/58.5gm/mole = 0.513mol/L x 2
=1.023mol/L
• For 2 L= 2x 1.023mol/L = 2.051mol/L = 2051mosmol/L
Thus the total ECF osmole = 3,920 + 2,051mosmo/L =
5,971mosmol/L
48
Steep two: determination of milliosmoles added

49. 49
Step 3: Determine the concentration in each L of solution
Table 3: Conditions after infusion before equilibrium

50.  Concentration= total miliosmoles in the body/ total volume
13,814/44 = 313.9mosml/L
 The fluid compartments will have the same concentration,
313.9mosml/L
 ICF volume = Total miliosmoles in ICF/ its concentration
= 7840/313.9 = 24.89L
ECF volume = total milimoles in ECF/ its concentration
= 5971/313.9 = 19.02L
50
Steep 4: determination of volume & concentration
after osmotic equilibrium is developed

51. The result (after infusion and equilibrium)
51
Table 4: conditions after equilibrium

52. Active Transport
• Transporter proteins (pumps) use energy
– Pump mediated and bulk transport
– Energy sources: ATP and ions
• Against concentration gradient.
• Gradient elevated
• Example Na+-K+ pump, Ca++ pump, movement of amino acids
into cell and movement of calcium into SR
52

53. Transporter proteins
Proteins
Cotransporter
Uniportor Symporter Antiporter/exchanger
Example Na+, Ca++, K+ ,
H+ channels
Na+-glucose or Na+-
amino acid
transporters ,Na+- K+
and 2Cl-
Na+-K+ (neurons), Na+-
Ca++ (heart cells), K+ -
H+ (kidney and
stomach) exchangers
53
Table 5: Transporter proteins

54. A) Ion driven
 Down hill ion movements uphill the solutes
 Indirect source of energy is ATP
B) ATP-driven: primary or direct
 ATP hydrolyzed by ATPase to drive uphill solute
Two types active transport
54

55. Mechanism of Na+- K+ pump and the functions
55
1. Regulate cell volume
2. Create membrane potential
(electrogenic effect): electrogenc
effect
3. Maintain ion diffusion gradient
4. Contribute for 20 active
transport
Fig 19: Sodium- potassium pump

56. 2) H+ -K+ pump on parietal cells apical membrane
56
Fig 20: Hydrogen- potassium pump

57. Secondary active transport
57
Na+
Secondary active
transport
Fig 21 : 20 active transport