active and passive transport of plasma membrane

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active and passive transport of plasma membrane

  1. 1. Membrane transport by E.ANANTHARAJ,1st msc ,cas in botany University of madras Introduction; The plasma membrane is a selectively permeable barrier between the cell and the extracellular environment. Its permeability properties ensure that essential molecules such as ions, glucose, amino acids, and lipids readily enter the cell, metabolic intermediates remain in the cell, and waste compounds leave the cell. Movement of virtually all molecules and ions across cellular membranes is mediated by selective membrane transport proteins embedded in the phospholipid bilayer.
  2. 2. Passive transport
  3. 3. Passive Transport A process that does not require energy to move molecules from a HIGH to LOW concentration  Diffusion  Facilitated Diffusion  Osmosis
  4. 4. • Diffusion is the movement of small particles across a selectively permeable membrane like the cell membrane until equilibrium is reached. These particles move from an area of high concentration to an area of low concentration. outside of cell inside of cell
  5. 5. • Facilitated Diffusion is the movement of larger molecules like glucose through the cell membrane – larger molecules must be “helped” Proteins in the cell membrane form channels for large molecules to pass through Proteins that form channels (pores) are called protein channels outside of cell inside of cell Glucose molecules
  6. 6. • Osmosis is the diffusion of water through a selectively permeable membrane like the cell membrane Water diffuses across a membrane from an area of high concentration to an area of low concentration. Semi-permeable membrane is permeable to water, but not to sugar
  7. 7. Active Transport • Cells may need to move molecules against concentration gradient – shape change transports solute from one side of membrane to other – protein “pump” conformational change – “costs” energy = ATP low ATP high “The Doorman”
  8. 8. Active transport • Many models & mechanisms ATP ATP antiport symport
  9. 9. summery Passive Transport Process Energy Source Example Simple diffusion Kinetic energy Movement of O2 through membrane Facilitated diffusion Kinetic energy Movement of glucose into cells Osmosis Kinetic energy Movement of H2O in & out of cells Filtration Hydrostatic pressure Formation of kidney filtrate
  10. 10. Active Transport Process Energy Source Example Active transport of solutes ATP Movement of ions across membranes Exocytosis ATP Neurotransmitter secretion Endocytosis ATP White blood cell phagocytosis Fluid-phase endocytosis ATP Absorption by intestinal cells Receptor-mediated endocytosis ATP Hormone and cholesterol uptake Endocytosis via caveoli ATP Cholesterol regulation Endocytosis via coatomer vesicles ATP Intracellular trafficking of molecules
  11. 11. REFERENCES Books ; .1.Molecular cell biology 5th edition .Lodish et.al 2.p.s verma &v.k agarwal Online source; 1,www.biology junction.com 2,www.uma.maine.edu 3,www.ocuy.org.

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