A brief overview of Plasma membrane transport

1. Membrane Transport
“The Ministry of Trade and
Commerce for the cell”

2. Source: Molecular cell biology, Lodish, 7th Ed.

3. Types of Transport
Based on the need for energy:
Passive
Simple Diffusion
Facilitated Diffusion
Active
Primary Active Transport
Secondary Active Transport

4. Movement along a concentration or electrochemical
gradient
Rate of diffusion is directly proportional to
Electrochemical gradient
Hydrophobicity
Temperature
Simple Diffusion
Source: Lehninger 5th edition

5. Source: Lehninger 5th edition
Need for Facilitated
transport ?
(transport proteins)

6. Facilitatory transport proteins can be…
Carrier proteins:
High stereo specificity.
Transport rates very low than
diffusion.
Transporter saturation.
Channel proteins:
Low stereo specificity.
Transport rates comparable to
diffusion.
No transporter saturation.
Can be gated.
Lehninger 5th edition
Eg. Glucose Transporter (GLUT)
Eg. Voltage gated K+ channel

7. Active Transport –
against electrochemical gradient
Primary Active Transport:
The endergonic reaction is
coupled to exergonic
chemical reaction.
ATP ADP + Pi
Lehninger’s Textbook of Biochemistry, 5thed
Eg. Sodium Potassium ATPase

8. Secondary Active Transport
The transport through one
tranporter is coupled to active
transport in another
Lehninger’s Textbook of Biochemistry, 5thed
Eg. Sodium – Glucose Co-transporter

9. Directional transport
Eg:
Uniport: Voltage gated ion
channels in CNS.
Symport: Na- Glucose transporter
in Intestine.
Antiport: Cl-Bicarbonate
exchanger in RBCs.
Lehninger’s Textbook of Biochemistry, 5thed

10. Ionophores
Eg.
Oligomycin
Uncoupler - transports the H+
ions , breaks the ETC.
Valinomycin
Masks the K+ ions, transports it
across the membranes.
Thereby breaks the
electrochemical gradient
across the membranes.
Lehninger’s Textbook of Biochemistry, 5thed

11. Solvent Transport
AquaporinsOsmosis
Lehninger’s Textbook of Biochemistry, 5thed

12. Aquaporins

13. Macromolecular (Vesicular) Transport
Exocytosis
Involvement of
Synaptobrevin and
Syntaxin.
Under the control of
membrane potential
Eg. Neurotransmitter
release.
Endocytosis
- Phagocytosis
- Fluid phase Endocytosis
(Pinocytosis)
Receptor mediated
endocytosis. – Selective
uptake of specific
molecules
Eg. LDL intake into hepatic
cells.

14. Thank You!