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Topic 1.4 Membrane TransportIB Biology
R. Price
v. 1 2015
Allott 33
#1: Particles move across membranes by simple diffusion, facilitated diffusion, osmosis, and active transport
Simple diffusion• Movement down the
concentration gradient• Phospholipid bilayer is
permeable to the particles (non-polar, like oxygen. Small, like urea)• No ATP
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#1: Particles move across membranes by simple diffusion, facilitated diffusion, osmosis, and active transport
Facilitated Diffusion• Movement down the concentration
gradient• Needs channels• Useful for ions• Cells can control types of channels
and channel placement• No ATP
#1: Particles move across membranes by simple diffusion, facilitated diffusion, osmosis, and active transport
Osmosis• Movement of water• Water moves from area of low solute
concentration to areas of high solute concentration• Happens in *all* cells• No ATP
#1: Particles move across membranes by simple diffusion, facilitated diffusion, osmosis, and active transport
Active Transport• Movement of substance from
lower concentration to higher concentration• Up the concentration gradient• Uses pump proteins• Uses ATP• E.g. firing of nerve cells
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#2: The fluidity of membranes allow materials to be taken into cells by endocytosis or released by exocytosis#3: Vesicles move materials within cells
Vesicles• Small sac of membrane with a
droplet of fluid inside• Proteins in the membranes use
ATP to make vesicles• Vesicles formed by pinching off a
small piece of the inside of the plasma membrane• Used for large molecules By Andrew Lacis [Public domain], via Wikimedia Commons
#2: The fluidity of membranes allow materials to be taken into cells by endocytosis or released by exocytosis#3: Vesicles move materials within cells Allott 34, 35
#2: The fluidity of membranes allow materials to be taken into cells by endocytosis or released by exocytosis#3: Vesicles move materials within cells Allott 35
Sources
Content Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014 ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.
Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge: Cambridge UP, 2014. Print.
ImagesUnless otherwise noted, images are obtained from Pixabay (www.pixabay.com) and used under the CC0 Public Domain license.
