passive osmosis active special types

1. Edited by
Dr Dina Merzeban
physiology lecturer
Fayoum university
Dina.Merzeban@Fayoum.edu.eg

2.  It consists of the phospholipid bilayer with embedded proteins.
 selectively permeable to ions and organic molecules
 controls the movement of substances in and out of cells.
 protect the cell from its surroundings.
CELL MEMBRANE

3. Transport through cell membrane
 Passive transport or diffusion
 Active transport

4. PASSIVE TRANSPORT or
DIFFUSION:
 Molecules move down their concentration
gradient.
 Molecules reach an equilibrium where they are
evenly distributed.
 PASSIVE

5. Simple diffusion
It is further devided into:
 1- Simple diffusion
through lipid layer
 2- Simple diffusion
through protein layer
 3- Facilitated or carrier-
mediated diffusion

6. SIMPLE DIFFUSION THROUGH LIPID
BILAYER
•
 Lipid layer of the cell membrane is permeable to lipid
soluble substances
 The diffusion through lipid layer is directly proportional to
the solubility.
1. Oxygen, Carbon dioxide – Non-polar.
2. Water – Polar but very small-high kinetic energy

7. SIMPLE DIFFUSION THROUGH
PROTEIN LAYER
 Proteins form channels for diffusion of water soluble substan
 They are either Ungated channels or Gated channels.
Gated channels:
1- Voltage-gated channels.
2 Ligand-gated channels.
3 Mechanically gated channels.

8. FACILITATED
DIFFUSION:
 Large polar molecules
such as glucose and amino
acids
 PASSIVE
 With concentration gradient

9. FACTORS THAT DETERMINE THE RATE OF
DIFFUSION:
1.The steepness of the concentration gradient.
2.Temperature.
3.Solubility of the substance.
4.permeability of the cell membrane.
5.Thickness of the cell membrane
6.Size of the molecule.
7.Size of the ions.
8.Charge of the ions.

11. OSMOSIS
The passive movement of solvent molecules through a
semi-permeable membrane(permeable to water and
impermeable to solutes) into a region of higher solute
concentration.

12. OSMOTIC PRESSURE
 Osmotic pressure is the pressure created by solutes in
a fluid during osmosis.
 The external pressure required to prevent osmosis
 Osmotic pressure is a colligative property:
It means that, osmotic pressure depends upon the
molar concentration of the solute but not on the identity.

14. ONCOTIC PRESSURE OR
COLLOIDAL OSMOTIC PRESSURE:
 Is the part of the osmotic pressure created by the larger colloidal
substances particularly protein .
 Albumin creates 70% of oncotic pressure. Normal oncotic pressure
is about 25mm hg.

15. Importance of osmotic pressure:
1- Fluid Balance
2- Blood volume (osmosis significantly
contributes to the regulation of blood volume and
urine excretion).
3- Transfusion (isotonic solution of NACL or
glucose are commonly used in i/v transfusion in
hospital for treatment of dehydration, burns
etc).

17. SUBSTANCES TRANSPORTED
BY ACTIVE TRANSPORT:
Substances, which are transported actively,
are in ionic form and non-ionic form.
 ionic as sodium, potassium, calcium,
hydrogen, chloride and iodide
 non-ionic as glucose, amino acids and
urea.

18. „CARRIER PROTEINS OF
ACTIVE TRANSPORT
1. Uniport
2. Symport or antiport.

19. PROPERTIES OF ACTIVE
TRANSPORT
 Active
 Needs carrier
 Against concentration gradient

20. TYPES ACTIVE TRANSPORT:
It is further devided into:
A- Primary active transport
B- Secondary active transport

21. Primary active transport
 The energy is derived directly from the
breakdown of ATP.

22. SECONDARY ACTIVE TRANSPORT
 In the secondary active transport, the energy is derived
secondarily from energy that has been stored in the form of
ionic concentration differences between the two sides of a
membrane.
 Secondary active transport is the transport of a substance
with sodium ion, by means of a common carrier protein.
When sodium is transported by a carrier protein, another
substance is also transported by the same protein
simultaneously, either in the same direction (of sodium
movement) or in the opposite direction. Thus, the transport of
sodium is coupled with transport of another substance.
Types of secondary active transport :
1- Cotransport, 2-Countertransport

24. ACTIVE TRANSPORT VS
FACILITATED DIFFUSION
Active transport mechanism is different from facilitated diffusion
by two ways:
1.Carrier protein of active transport needs energy, whereas
the carrier protein of facilitated diffusion does not need
energy
2.In active transport, the substances are transported against the
concentration or electrical or electrochemical gradient. In facilitated
diffusion, the substances are transported along the concentration or
electrical or electrochemical gradient.

25. SPECIAL TYPES OF PASSIVE
TRANSPORT
BULK FLOW:
Bulk flow is the movement of large
quantity of substances from a region of
high pressure to the region of low
pressure.
It is due to the pressure gradient of the
substances across the cell membrane

26. Bulk flow

27. FILTRATION:
Movement of
water and
solutes from an
area of high
hydrostatic
pressure to an
area of low
hydrostatic .

28. SPECIAL TYPES OF ACTIVE
TRANSPORT
1. Endocytosis
2. Exocytosis
3. Transcytosis.

29. Endocytosis
 Endocytosis is defined as a transport
mechanism by which the macromolecules
enter the cell.
types:
1.Pinocytosis
2.Phagocytosis
3.Receptor-mediated endocytosis

30. PINOCYTOSIS:
Pinocytosis is a process by which macromolecules like
bacteria and antigens are taken into the cells. It is
otherwise called the cell drinking.

31. Phagocytosis:
 Phagocytosis is the process by which particles
larger than the macromolecules are engulfed into the
cells.
 It is also called cell eating.
 Larger bacteria, larger antigens and other larger
foreign bodies are taken inside the cell by means of
phagocytosis.
 Only few cells in the body like neutrophils,
monocytes and the tissue macrophages show
phagocytosis.
 Among these cells, the macrophages are the largest
phagocytic cells.

32. MECHANISM OF PHAGOCYTOSIS
i.When bacteria or foreign body enters the body, first the phagocytic cell
sends cytoplasmic extension (pseudopodium) around bacteria or
foreign body.
ii.Then, these particles are engulfed and are converted into endosome
like vacuole. Vacuole is very large and it is usually called the
phagosome.
iii. Phagosome travels into the interior of cell.
iv.Primary lysosome fuses with this phagosome and forms secondary
lysosome.
v.Hydrolytic enzymes present in the secondary lysosome are activated
resulting in digestion and degradation of the phagosomal contents.

33. RECEPTOR-MEDIATED
ENDOCYTOSIS
 The transport of macromolecules with the help of a receptor protein.
 Surface of cell membrane has some pits (receptor-coated pit)
which contain a receptor protein called clathrin.
 These receptor-coated pits are involved in the receptor-
mediated endocytosis.

34. Mechanism of receptor-mediated
endocytosis:
 Receptor-mediated endocytosis is induced by
substances like ligands
 Ligand molecules approach the cell and bind to
receptors in the coated pits and form ligand-
receptor complex.
 Ligand-receptor complex gets aggregated in the
coated pits. Then, the pit is detached from cell
membrane and becomes the coated vesicle. This
coated vesicle forms the endosome.

35.  Primary lysosome in the cytoplasm fuses with endosome and
forms secondary lysosome.
 Now, the hydrolytic enzymes present in secondary lysosome
are activated resulting in release of ligands into the
cytoplasm.
 Clathrin is recycled into a new pit of the cell Membrane.

36. TRANSCYTOSIS:
 Transporting the substances between two
environments across the cells without any
distinct change in the composition of these
environments.
 Trans-cytosis is a transport mechanism in which
an extracellular macromolecule
 Enters through one side of a cell,
 migrates across cytoplasm of the cell
 and exits through the other side.

37. MECHANISM OF TRANSCYTOSIS
 Transcytosis involves the receptor-coated pits as in
receptor-mediated endocytosis.
 Receptor protein coating the pits is caveolin and not
clathrin.
 Transcytosis is also called, vesicle trafficking.
 Examples
 the movement of proteins from capillary blood into
interstitial fluid across the endothelial cells of the
capillary.
 pathogens like human immuno deficiency virus (HIV)