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Transporting Molecules Across Cell Membranes: An Overview

Cell membranes, also known as plasma membranes, are primarily composed of phospholipids and proteins, facilitating the selective permeability essential for cellular function. Molecules move across these membranes via diffusion, which occurs from areas of higher concentration to lower concentration. Various transport types, including passive transport (like diffusion and osmosis) and active transport, enable cells to manage the movement of substances. Notably, integral proteins and glycoproteins play key roles, including the recognition of self. Understanding these mechanisms is crucial for insights into cellular processes.

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Transporting Molecules Across Cell Membranes: An Overview

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  1. Transporting Molecules

  2. CELL MEMBRANE(also called plasma membrane) Cell membranes are made of ________________ & __________________ PHOSPHOLIPIDS PROTEINS

  3. CELL MEMBRANE Proteins that stick on the surface = _____________(either inside or outside of cell) Proteins that stick INTO membrane = ________________ (can go part way in or all the way through)

  4. GLYCOPROTEINS Recognize “self” GLYCOPROTEINS are INTEGRAL PROTEINS

  5. SELECTIVELY PERMEABLE(semi-permeable)

  6. Diffusion http://lhs.lps.org/staff/sputnam/Biology/U3Cell/diffusion_1.png

  7. Animatioin from: http://www.biologycorner.com/resources/diffusion-animated.gif Molecules move from “where there’s A LOT” to “where there’s NOT”

  8. DIFFUSION across a space • Happens anytime there is a __________ in concentration in one place compared to another (________________________)

  9. DIFFUSION across a space • Molecules move automatically from an area of _______ concentration to an area of ________ concentration • EX: _____________________ _____________________ Perfume, Koolaid, popcorn, BBQ, Bad smell in room http://leighhouse.typepad.com/blog/images/kool_aid.jpg http://www.swapmeetdave.com/Humor/Farts.htm

  10. Molecules need to move across membranes in cells Image modiified from: http://www.accessexcellence.org/AB/GG/importProt.html

  11. Diffusion can happen across a membrane in a cell …as long as membrane will let molecule through

  12. SELECTIVELY PERMEABLE

  13. Gas exchange between lungs and blood happens by DIFFUSION from HIGHER concentration to LOWER concentration Image modified from: http://www.medaille.edu/vmacer/120_graphic_05oxygen.gif

  14. What if cell needs to move large or polar molecules? EX: _______________ _______________

  15. What if cell needs to move a molecule AGAINST the CONCENTRATION GRADIENT? Example : (LOW HIGH) _______________________ Image from: http://www.biologyclass.net/mitochondria.jpg

  16. What if cell needs to move molecules really FAST? (can’t wait for it to diffuse) Example in cells: Movement of ________________ ions sends nerve signals http://www.steve.gb.com/images/science/neuron.png

  17. 2 KINDS of TRANSPORTacross cell membranes • _____________TRANSPORT Does NOT require energy • ___________TRANSPORT Requires energy

  18. Kidspiration by: Riedell

  19. Kinds of Passive Transport __________________________________ ___________________________________ ___________________________________ ___________________________________

  20. DIFFUSION across a membrane • Happens anytime there is a __________ in concentration on one side of the membrane compared to the other Molecules that move by diffusion across membranes in cells: ______________ ______________ http://www.lionden.com/cell_animations.htm

  21. OSMOSIS = SPECIAL KIND OF DIFFUSION • MOVES WATER MOLECULES • Across a MEMBRANE • From HIGHER  LOWER http://www.Isbu.ac.uk/water/molecule.html

  22. DIFFUSION Can happen with or without a membrane Molecules that do it: All molecules EXCEPT water Goes until equilibriumExample in cells: Oxygen & Carbon dioxide OSMOSIS Happens across a membraneMolecules that do it:Water Goes until equilibriumExample in cells:Water DIFFUSION or OSMOSISHIGHER  LOWER

  23. What if there is a difference in concentration but solute molecules can’t move across a membrane? WATER will move until concentration reaches equilibrium

  24. Osmosis1 http://www.sidwell.edu/us/science/vlb6/labs/a_osmosis.gif

  25. Kinds of Passive Transport __________________________________ ___________________________________ ___________________________________ ___________________________________ • Diffusion • Osmosis • Facilitated Diffusion • Ion Channels

  26. Facilitated DiffusionCarrier proteins help diffusion go faster

  27. FACILITATED DIFFUSION • Passive = ____________________ • Moves from ________________________ • _____________________ bind molecule, change shape, and release it on other side of membrane (Carrier proteins are _______________ proteins) • Molecules that move this way in cells: _______________________

  28. Facilitated Diffusion Animation from: http://bio.winona.edu/berg/ANIMTNS/facdifan.gif

  29. Kinds of Passive Transport __________________________________ ___________________________________ ___________________________________ ___________________________________ • Diffusion • Osmosis • Facilitated Diffusion • Ion Channels

  30. ION CHANNEL

  31. ION CHANNELS • _____________transport (no energy required) • Molecules move from ___________________ • Small passageways for _______ to get through membrane • Each ion has own kind of passageway • Examples in cells: Na+, Cl- , Ca + + , K +

  32. ION CHANNELS Some channels always open Some channels have “gates” that open or close in response to signals • SIGNALS: • stretching of cell membrane • electrical signals • chemicals Animation from: http://www2.uic.edu/~myilma1/ionchannel.gif

  33. Kidspiration by: Riedell

  34. Kinds of Active Transport ________________________________________ ___________________________________ ____________________________________

  35. SODIUM-POTASSIUM PUMP • ___________ transport (requires energy from ______) • Special just for Na+and K +ions • Uses integral ___________________ to move molecules • Examples in nerve cells: Na+is pumped out of cells at same time K +is taken into cells

  36. Na+and K + PUMP Animation from: http://www.lionden.com/cell_animations.htm

  37. ENDOCYTOSISTakes substances into cell • _____________transport (requires energy from ATP) • Uses small membrane sacs to carry substances ______________ http://www.sirinet.net/~jgjohnso/cell.html

  38. 2 KINDS of ENDOCYTOSISTakes substances into cell If taking in: fluid, molecules = ____________________ large particles or whole cells = __________________ • Examples in cells: • one celled organisms eat this way • white blood cells get rid of bacteria this way

  39. ENDOCYTOSIS Animation from: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/cell-movement.html

  40. PHAGOCYTOSIS White blood cell destroying germs

  41. EXOCYTOSISSubstances released outside of cell • __________ transport (requires energy) • Substances move in____________ • Examples in cells: • Golgi release packaged proteins

  42. Exocytosis http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBooktransp.html

  43. GOLGI BODIES USE EXOCYTOSIS Animation from: http://www.franklincollege.edu/bioweb/A&Pfiles/week04.html

  44. Endocytosis & Exocytosis http://grossmont.gcccd.cc.ca.us/cmilgrim/Bio120/Outline/Outline2.gif/TransportMedia/EndoExocytosisMovie.htm

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