Active Transport

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Active Transport:

Presented by: saiesh phaldesai 1 st Yr M.Pharm Pharmaceutics SCP Active Transport

Active Transport:

Active Transport Movement of solutes from an area of low concentration to higher concentration. Cell uses energy and actively moves molecules to where they are needed. It is not dependent on concentration gradient. Allows for greater accumulation of the substance on one side of the membrane than the other side. As the process requires expenditure of energy, it can be inhibited by metabolic poisons that interfere with energy production like fluorides, cyanides etc. Important in renal and biliary excretion of many drugs and their metabolites and secretion of certain acids out of the CNS.

Types of Active Transport:

Types of Active Transport Protein Pumps: Transport proteins that require energy to do work. i . Exchange Pumps:Sodium Potassium Pump. Important for Nerve Impulses and Muscle Control. ii. Ion Pumps: Actively transport Sodium,Potassium,Calcium and Chlorine.

Sodium-Potassium Pump:

Binding of cytoplasmic Na+ to the pump protein stimulates phosphorylation by ATP. 1 2 3 4 Phosphorylation causes the protein to change its shape. The shape change expels Na + to the outside, and extracellular K + binds. 5 Loss of phosphate restores the original conformation of the pump protein. K + binding triggers release of the phosphate group. 6 K + is released and Na + sites are ready to bind Na+ again; the cycle repeats. Concentration gradients of K + and Na + Extracellular fluid Cytoplasm Sodium-Potassium Pump Figure 3.10


2 . Endocytosis : Taking bulky material in a cell. Uses energy,cell membrane in-folds around food particle also called “Cell eating” forms food vacuole and cellular enzymes digests food. Ex: White blood cells eat bacteria,phagocytosis . 3. Exocytosis : Forces material out of cell in bulk. Membrane surrounding the material fuses with the cell membrane,cell changes shape,requires energy. Ex: Hormones or wastes released from cell.

Secondary Active Transport:

Secondary Active Transport Ions or molecules move in same ( symport ) or different ( antiport ) direction. Ex:Cotransport of Na + and glucose. A sodium-potassium exchange pump maintains a concentration of Na that is higher outside the cell than inside. Active transport. Na moves back into the cell by a carrier protein that also moves glucose. The concentration gradient for Na provides the energy required to move glucose against its concentration gradient.

PowerPoint Presentation:

Endocytosis is of three major types: Phagocytosis: ‘Cell eating’, Keeps the tissue free of debris and microorganisms. Pinocytosis: ‘Cell drinking’ Receptor Mediated Endocytosis.

Phagocytosis or ‘Cell eating’:

Phagocytosis or ‘ Cell eating ’


Pinocytosis Taking in droplets of ECF occurs in all human cells Not as selective as ‘receptor-mediated endocytosis’ Membrane caves in, then pinches off into the cytoplasm as pinocytotic vesicle E.g. Absorption of Sabine Polio Vaccine and large protein molecules.

PowerPoint Presentation:


Receptor Mediated Endocytosis:

Receptor Mediated Endocytosis A selective process. Involves formation of vesicles at surface of membrane Vesicles contain receptors on their membrane Vesicles contain specific target molecule in high concentration. Clathrin-coated vesicle in cytoplasm uptake of LDL from bloodstream If receptors are lacking, LDL’s accumulate and hypercholesterolemia develops



Active Membrane Transport Review:

Active Membrane Transport Review Process Energy Source Example Active transport of solutes ATP Movement of ions across membranes Exocytosis ATP Neurotransmitter secretion Endocytosis ATP White blood cell phagocytosis Receptor-mediated endocytosis ATP Hormone and cholesterol uptake


Reference Cell transport, Biopharmaceutics and Pharmacokinetics, V Venkateswarlu,Second Edition. Biopharmaceutics and Pharmacokinetics,D.M.Brahmankar.

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