IB Biology - Passive Transport (Diffusion, Facilitated Diffusion, Osmosis)
Chapter 1.4 - Membrane Transport
Particles move across membranes by simple diffusion, facilitated diffusion, osmosis
Application: Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis.
Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions.
In the last IB biology chapter 1.3 we mention the cell membrane is semipermeable, guarding the material exchange in the cell membrane. Passive transport is one of the methods to cross the membrane.
Concentration gradient occurs when the concentration of molecules in two regions are imbalance
Simple diffusion = molecules move down by the concentration gradient until the molecules are evenly distributed
Carrier Mediated Simple Diffusion
osmosis = water moves across the partially permeable membrane from the low solute concentration area to the high solute concentration
osmolarity = the description of the concentration of solute in 1L solution
Water potential = the tendency of water to move and leaveincrease the osmolarity, decrease the water potential
Experiment to determine the Osmosis
How to determine if a substance lets say potato is hypertonic or hypotonic to a solution?
0% salt, 0.1% salt, 0.2% salt, ........., 0.9% salt, 1% salt
% change = (change in the mass / original mass )x100
In this IB biology chapter, you have to:
1. how things moved by the diffusion
2. distinguish the differences in different formats of diffusion
3. be awarded that things are equally distributed doesn't mean they don't move, actually, they do but just with no net movement
4. In diffusion, the molecules move from high to low conc. area, but in osmosis, water moves from low salt to high salt area
5. the relationship between osmolarity and water potential
That is the end of the topic.
Wanna Boost Up Your IB Biology? Check out our study tips here!
Written by Queenie l IBDP Biology Specialist @ TUTTEE
1. Khan Academy, https://www.khanacademy.org/science/biology/membranes-and-transport/passive-transport/a/diffusion-and-passive-transport
2. Socratic Q&A, https://socratic.org/questions/what-is-the-role-of-protein-channels-in-the-cell-membrane
3. BYJUS, https://byjus.com/biology/diffusion/
4. Labroots, https://www.labroots.com/tag/carrier-protein
5. Wiki, https://en.wikipedia.org/wiki/Osmosis
6. Brenda Walpole (2014). Biology for the IB Diploma (Second Edition). Cambridge University Press.
7. Change.org, https://www.change.org/p/nhs-approve-iv-saline-therapy-for-the-treatment-of-pots-under-the-nhs
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