About physiology of transportation

1. Transport across cell membrane
• Active transport
• Passive transport

2. Active transport
• Transport of substance against concentration
gradient
• Also known as uphill movement
• Requires energy
• Provided by hydrolysis of ATP
• Two types
– Primary
– Secondary

3. Primary active transport
• Energy liberated directly from the breakdown
of ATP
• Eg: Na+K+- ATPase pump

5. Secondary active transport
• Transport of a substance with sodium ion, by
means of a common carrier protein
• Indirectly uses energy obtained from
hydrolysis of ATP

7. Types of secondary active transport
• Symport- transport 2 substances together in
the same direction
• Example- sodium/glucosesymporter
– sodium/aminoacid symporter
• Antiport- transports 2 substances in opposite
directions
• Example- sodium/calciumexchanger,
sodium/hydrogenexchanger.

9. Vesicular transport
• Special type of active transport
• Types
✓Endocytosis
✓Exocytosis
✓Transcytosis

10. Endocytosis
• Materials move into a cell in a vesicle formed
from the plasma membrane

11. Types of endocytosis
• Pinocytosis
• Phagocytosis
• Receptor mediated endocytosis

12. Pinocytosis (cell drinking)
• Pinocytosis is the fluid-phase endocytosis or
‘cell drinking’ by which substances in solution
in extracellular fluid are internalized to the
cell.
• Pino means “to drink”

13. Phagocytosis (cell eating)
• Phago means ‘to eat’
• Phagocytosis is the process of ingestion of
large particles or microorganisms by
specialized cells called phagocytes.
• In this process, the phagocytic cells, such as
macrophages engulf bacteria, foreign particles
and tissue debris and digest them

14. Receptor mediated endocytosis
• the extracellular molecule binds with the specific
receptor on the cell membrane, concentrated at a
depression on membrane called coated-pits.
• the coated-pit pinches off from the membrane in
the form of an endocytic vesicle causing rapid
internalization of the molecule.
• Hormones, growth factors, transport-proteins like
transferrin, toxins, viruses, etc. enter cells by
receptor mediated endocytosis.

16. Exocytosis
• Process by which substances move out of cell

17. Transcytosis
• Process in which the extracellular
macromolecule enters through one side of a
cell, migrates across cytoplasm and exits
through the other side
• Receptor protein- caveolin

18. Passive transport
• Transport of substance along concentration
gradient
• Also called downhill movement
• Does not need energy

19. Types of passive transport
• Simple diffusion
• Facilitated diffusion
• Osmosis

20. Simple diffusion
• Substancesmove freely through lipid bilayer of the plasma
membrane
• Does not need the help of membrane transport protein
• Example; diffusion of oxygen, carbon dioxide, nitrogen gases,
fat soluble vitamins

22. Facilitated diffusion
• Water soluble substances are transported
through the cell membrane with the help of a
carrier protein
• Example; glucose and amino acid transport

24. Osmosis
• Movement of water or any solvent from an
area of lower concentrationto an area of
higher concentrationof a solute through a
semi permeable membrane

25. • In osmosis, water moves to dilute the more
concentrated solution. Once concentrations
are equal, net movement of water stops.
• Important note: The semipermeable
membrane only allows the movement of
solvent molecules through it – solute particles
cannot pass through it

27. • Osmotic pressure is the minimum pressure
applied to the solution with higher solute
concentrationto prevent osmosis.
• Osmotic pressure in body fluid is mainly
exerted by osmotically active solutes dissolved
in the fluid such as colloidal substances.
Hence, the osmotic pressure is called colloidal
osmotic pressure

28. • Osmolality of a solution refers to the number of
osmoles (number of osmotically active particles)
dissolved in a kilogram of water
• Osmolarity refers to the number of osmoles in
one liter of plasma
• The normal plasma osmolality is 290 mOsm per
kg
• The important factor determining the osmotic
pressure of a solution is the concentration of the
particles released in solution (i.e. the osmoles),

29. • Tonicity refers to the osmolality of a solution in
relation to plasma (same osmotic pressure as
plasma).
• Isotonic Solutions, which have osmolality same
as that of plasma, like 0.9% NaCl, are said to be
isotonic.
• Hypotonic Solutions with lower osmolality are
said to be hypotonic.
• Hypertonic Solutions with higher osmolality than
that of plasma are said to be hypertonic.