This document discusses various mechanisms of transport across the plasma membrane. It begins by introducing passive transport, which moves substances along concentration gradients without requiring energy. Specific passive transport mechanisms discussed include simple diffusion, facilitated diffusion, bulk flow, filtration, and osmosis. Active transport is then covered, which moves substances against gradients and requires energy. Primary and secondary active transport mechanisms such as sodium-potassium pumps, calcium pumps, and sodium symport/antiport are explained. Special transport mechanisms like endocytosis, exocytosis, transcytosis, and molecular motors are also summarized. Finally, examples of applied physiology involving abnormalities of transport mechanisms are provided.

1. TRANSPORT THROUGH
PLASMA MEMBRANE

2. Discussion Matter
1. INTRODUCTION
2. BASIC MECHANISM OF TRANSPORT
3. PASSIVE TRANSPORT
4. SPECIAL TYPE OF PASSIVE TRANSPORT
5. ACTIVE TRANSPORT
6. SPECIAL TYPE OF ACTIVE TRANSPORT
7. MOLECULAR MOTORS
8. APPLIED PHYSIOLOGY

3. INTRODUCTION
- Through the transport mechanism across cell
membrane:
+ The cell in the body must be supplied with essential
substances.
+ Must get rid many unwanted substances.
- Essential: water, nutrients, electrolytes, etc.
- Unwanted: waste products, CO2, etc.
Who is the actors for this transport?
LIPID & PROTEIN

4. BASIC MECHANISM
PASSIVE TRANSPORT MECHANISM
ACTIVE TRANSPORT MECHANISM

5. PASSIVE TRANSPORT
MECHANISM
High
Concentration
Region
Low
Concentration
Region

6. Passive transport?
- The transport of substances along the
concentration gradient OR electrical gradient OR
BOTH (electrochemical gradient).
- Higher concentration lower concentration
- Does not need energy
- Downhill movement/ diffusion.

7. 2 Diffusion
1. Simple Diffusion
- Simple diffusion through lipid layer
- Simple diffusion through protein layer
2. Facilitated Diffusion
- Facilitated or carrier-mediated diffusion

8. Simple Diffusion Through Lipid Layer
- Directly proportional to the solubility of
substances in lipids.
- Lipid layer of the cell membrane is
permeable only to lipid soluble
substances. (O2, CO2, alcohol)

10. Simple Diffusion Through Protein
Layer
- Electrolytes diffuse through protein layer
- Protein layer is permeable to water-soluble
substances.
1. Protein Channel/Ion Channel
- Pores
lined up by the integral protein
molecules.
hypothetical pores.
Form the channel for diffusion of water.

11. Continuation
2. Type of Protein/Ion Channel
- The channel are named after the ions
which diffuse through this channel.
- Ex: sodium channel, potassium channel,
etc.
WHY?
The characteristic features of protein
channel is selective permeability. Each
channel can permit only 1 type ion pass
through it.

12. Continuation…
3. Regulation of the Channels
- Ungated channels -> continuously
opened channels
- Gated channels -> closed channels
3 types -> voltage-gated channels
-> ligand-gated channels
-> mechanically gated channels

13. Continuation…
a. Voltage gated channels -> open whenever there
is a change in the electrical potential. Ex:
neuromuscular junction
b. Ligand gated channels -> open in the presence of
some hormonal substances (ligands).
c. Mechanical gated channels -> opened by some
mechanical factors. Ex: receptor cells.

14. Facilitated or Carrier-Mediated
Diffusion
 The type of diffusion by which the water
soluble substances having larger
molecules are transported through the cell
membrane with the help of carrier protein.
 Faster
 For glucose and amino acid?

15. Factors Affecting Rate of Diffusion
 Permeability of the Cell Membrane
 Temperature
 Concentration Gradient/Electrical Gradient of the
Substances across the Cell Membrane
 Solubility of the Substance
 Thickness of the Cell Membrane
 Size of the Molecules
 Size of the Ions
 Charge in the Ions

16. SPECIAL TYPE OF PASSIVE
TRANSPORT
 Bulk Flow -> diffusion of large quantity of substances :
high pressure region  low pressure region.
Ex: exchange gases across the respiratory membrane in
lungs.
 Filtration -> movement of water & solutes: high
hydrostatic pressure area  low hydrostatic area.
 Osmosis -> movement of water/any other solvent:
lower concentration area high concentration solute.

17. Continuation…

18. - Osmosis through semipermeable membrane.
- Osmotic Pressure -> pressure created by the solutes in a
fluid.
- Reverse Osmotic Pressure -> process in which
water/other solvent flows in reverse direction.
- Colloidal Osmotic Pressure -> osmotic pressure exerted
by colloidal substances.
- Oncotic Pressure -> osmotic pressure exerted by
colloidal substances (protein) of the plasma. It is about
25mm Hg.

19. 2 type osmosis:
1. Endosmosis -> movement of water into
the cell.
2. Exosmosis -> movement of water out
the cell.

20. ACTIVE TRANSPORT
 The movement of substances against the
chemical/electrical/electrochemical gradient.
 It is uphill transport.
 It is required energy

21. Active Transport vs Facilitated Diffusion
Active Transport Facilitated Diffusion
Carrier protein need energy Carrier protein does not need
energy
The substances are transported
against the concentration/
electrical/ electrochemical
gradient
The substances are transported
along the concentration/
electrical/ electrochemical
gradient

22. Carrier Protein of Active
Transport
Uniport
- Carries only 1 substances in a single direction.
- Uniport pump.
Symport or Antiport
- Symport ->transport 2 different substances in the same
direction.
- Antiport -> transport 2 different substances in opposite
direction.

23. Mechanism of Active Transport
Substances:
 Comes near the cell membrane
 Combines with the carrier protein
 Forms substances-proteins complex
 Complex moves towards the inner surface of the cell
membrane
 Released from the carrier proteins
 Same protein moves back to outer surface to transport
another substances.

24. Substances Transported
Ionic Non-ionic
Sodium
Potassium
Calcium
Hydrogen
Chloride
Iodide
Glucose
Amino acid
urea

25. 2 Types Active Transport
Primary Active Transport
Secondary Active Transport

26. PRIMARY ACTIVE TRANSPORT
 Type of transport mechanism in which the
energy is liberated directly from the
breakdown of ATP.

27. Sodium-Potassium Pump
 Sodium 7potassium transported across the cell
membrane.
 Na+-K+ ATPase pump
 Transport sodium: insideoutside cells
 Transport potassium: outsideinside cells
 Present in all cells of the body
 Responsibility -> distribution of sodium & potassium
ions across the cell membrane
-> development of resting membrane
potential

28. Sodium-potassium pum

29. Transport of Calcium Ion
 Actively transported from inside to outside of the cell by
calcium pump.
 Operated by a separate carrier protein.
 Energy from ATP by the catalytic activity of ATPase.
 Also present in some organelles. For move calcium into
organelles.

30. Transport of Hydrogen Ions
 Actively transported by hydrogen pump.
 Energy from ATP.
 The pump present in Stomach & Kidney.

31. SECONDARY ACTIVE TRANSPORT
 Transport of substance with sodium ion.
 When sodium is transported, another substance also
transported. Either in same direction or opposite.
 2 type: Cotransport & Counter transport

33. Sodium Cotransport
 Substance is transported by symport along with sodium.
 Movement energy from breakdown of ATP.
 Released energy utilized form movement another
substance.
 Substances: glucose, amino acid, chloride, iodine, iron,
urate.

34. Sodium cotransport

35. Sodium Counter Transport
 Substances are transported in exchange for sodium ion
by antiport.
 Various counter transport:
+ sodium-calcium counter transport
+ sodium-hydrogen counter transport
+ other counter transport system

36. Sodium counter transport

37. SPECIAL TYPE OF ACTIVE TRANSPORT
Endocytosis
Exocytosis
transcytosis

38. Endocytosis
 Mechanism by which macromolecules enter the cell.
 It cannot pas the membrane by passive or active transport
mechanism.
 3 types:
pinocytosis-> cell drinking, by which macromolecules like bacteria
and antigen are taken into cells.
Mechanism?

39. Phagocytosis-> Cell eating, particle larger than
macromolecules are engulfed into the cells.
Larger bacteria, larger antigen, other
larger foreign body.
Mechanism?

40. Receptor-mediated Endocytosis-> transport of
macromolecules with the help of a receptor protein.
->clathrin: receptor protein in surface od cell
membrane
-> receptor-coated pit: clathrin + pits cell
membrane.
Mechanism?

42. Exocytosis
 Process by which the substances are expelled out from the
cell.
 The substances are extruded from cell without passing through
the cell membrane.
 Role of Calcium? Calcium ion enter the cell and cause
exocytes.
 Mechanism?

43. Transcytosis
 Extracellular macromolecule enters through 1 side
of a cell, migrates across cytoplasm of the cell and
exits through the other side.
 Mechanism?

44. MOLECULAR MOTOR
 Protein based molecular machine that perform
intracellular movement in response to spesific stimuli.
 Function:
-transport of synaptic vesicle containing neuro transmitter
from the nerve cell body to synaptic terminal.
-role in cell division by pulling the chromosomes
Transport of viruses & toxins to the interior of the cell for its
own detriment.

45. Type of molecular motor:
- Kinesin
- Dynein
- Myosin

46. APPLIED PHYSIOLOGY
Abnormalities of sudium-potassium pump:
 Cause cardiac failure
 Hypertension
Ion channel diseases (caused by gen mutation that encode
the ion channels)
 sodium channel diseases : muscle spasm, Liddle’s
symdrome.
 Potassium channel disease: heart disorder, inherited
deafness, epileptic seizures in new born.
 Chloride channel diseases: renal stone, cystic fibrosa