DP IB Biology Topic 1-4 Membrane Transport

1. Topic 1.4 Membrane Transport
IB Biology
R. Price
v. 1 2015

2. Allott 33

3. #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

4. Allott 36

5. Allott 37

6. #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

7. #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

8. #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

9. Allott 39

10. Allott 39

11. Allott 40

12. Allott 40

13. Allott 41

14. Allott 41

15. Allott 42

16. Allott 42

17. Allott 43

18. Allott 43,44

19. Allott 44

20. #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

21. #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

22. #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

23. 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.
Images
Unless otherwise noted, images are obtained from Pixabay
(www.pixabay.com) and used under the CC0 Public Domain license.