EEOB 2520 Study Guide - Midterm Guide: Osmotic Concentration, Lipid Bilayer, Ion Channel
2 May 2018
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Exam 3 Material
Membrane Transport continued
Diffusion through lipid bilayer
• With concentration gradient, no E cost!
• Easiest for: Small, NP (ex:oxygen, carbon dioxide)- have the easiest time going through the
bilayer
• What problem does this cause?
o Concentration is lower so it will go outside the cell
o No oxygen storage in cells!
o Want to do something to keep O2 moving in our cells
• Solve this problem:
o Problem created by gradient being in the wrong direction, need it to convince Oxygen to
go into the cell on its own
o Need to store the oxygen outside the cell so that it will go inside the cell to balance out
(high to low concentration)
o It is the gradiet orret diretio
o The gadiet does’t oside a of the opoud if it is attahed to soethig else-
also, if we attach it to something else it will take on the traits of something else
o Ho to ake it so O is’t pat of the gadiet ut still get though? – attach it to
something else, deceive the gradient
o Attach oxygen to something once its inside the cell and change its characteristics of
the compound
o So make it something bigger, so it cannot go out and has to stay inside the cell
o What compound do we use to store oxygen as bound O2 NOT free O2? – myoglobin ( a
lot in muscles)
o deeie the gradient
Diffusion through protein
• A protein is in our membrane that goes across the phospholipid bilayer (called transmembrane/
integral)
• They create a way for polar components to go through without having to interact with the
nonpolar tail region- Creates a tunnel for them to go through nicely
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• Typically used by ions (why these called ion channels often)
• These ions diffuse through the channels- go high to low- no energy required- it does it itself
• Movement with the gradient, no energy cost
• FIGURE 4-7
Gating- how we adjust whether the protein is open or close
• It is normally closed and have to do something to the protein to get it to open to allow diffusion
to occur
• Ligand-gating: ligand binding to channel
o The compound ligand binds to the protein and makes it switch back and forth from open
and closed
o Anytime we bind something to a protein, we will change its shape!
o Only issue is the shape change is how much it will impact what we are trying to do with
the protein
o Ex: using a key to open car door
• Voltage-gated: change the electrical activity around the protein (change in electrical
distribution)
o Proteins can change shape based on this electrical activity
o ex: using the remote to open car- need batteries for it to work
• Mechanically-gated: membrane stretched
o Ex: like breaking into a car- do it by force
o Bc bilayer is fluid mosaic model- it is always moving and flowing, so can just pull the
protein open to let things through
• Any particular channel will work based on one of these gates- they do one of these
Special case
▪ Another compound moving through a channel
▪ The ae’t ios- called aquaporins
▪ Aqua= water, Porin= opening
▪ Water moves through these- they are water channels
▪ Ways to let water move more quickly in and out of the cell
How does this water move?
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• Water moves through these channels based on osmosis
Osmosis
• Net diffusion of water across a membrane
• FIGURE 4-16
• Water moves high to low concentration! ( high to low [water])
• Water is our base big component, it is easier to focus on what is NOT water (solutes)-everything
that is NOT water IS a solute
• Wate’s oeet is toads the highe solute oetatio
• From low to high [solute]
• These are the same! Water moving from high to low concentration of water is the same as
saying water moving from low to high solute concentration (because a high solute means low
water)
• Water moves towards the higher Osmolarity- it is related to the solute concentration not the
water concentration
• To figure out which way water should go, look at concentration of solutes not amount of
water
• Measurement= osmolarity
o Total [solutes] in a solution
o [x] = (# of x) / volume
▪ X= solutes
o Ex: 3 mol MG 2+ + 2 mol of glucose in 1 L= 5 Osm
▪ (3 mol + 2 mol)/ 1 L= 5/1= 5 Osm
o Ex: 3 mol of MgCl2 + 2 mol glucose in 1 L= 11 Osm
▪ MgCl2 is an ionic compound- it has a weak bond in water and dissolves
▪ The 3 mols of MgCl2 becomes 3 mols of Mg and 3 mols of each Cl
▪ [3 mol Mg + 2 (3 mol Cl-) + 2 mol glucose}/ 1 L = 11 Osm
▪ Ions expected to know= MgCl2, NaCl2, H+
▪ This will be the most difficult kind of problem we will have
▪ Ex: if divide by half a liter, it will be multiplied instead of divided by
o Increase osmolarity= decrease [water]
▪ More osmolarity means more solutes so less space for water
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find more resources at oneclass.com
Document Summary
Myoglobin ( a lot in muscles) (cid:862)de(cid:272)ei(cid:448)e(cid:863) the gradient. Gating- how we adjust whether the protein is open or close. It is normally closed and have to do something to the protein to get it to open to allow diffusion to occur. Special case: another compound moving through a channel. The(cid:455) a(cid:396)e(cid:374)"t io(cid:374)s- called aquaporins: aqua= water, porin= opening, water moves through these- they are water channels, ways to let water move more quickly in and out of the cell. How does this water move: water moves through these channels based on osmosis. [3 mol mg + 2 (3 mol cl-) + 2 mol glucose}/ 1 l = 11 osm. Ions expected to know= mgcl2, nacl2, h: this will be the most difficult kind of problem we will have, ex: if divide by half a liter, it will be multiplied instead of divided by. We pay attention to these not the water.
