Membrane Transport Flashcards
What kind of medication is Prilosec?
A proton pump inhibitor!
Define hypertonic?
Higher concentration outside the cell than inside, so pulls water from cells to outside!
Define isotonic?
When extracellular and intracellular concentration is balanced, no net movement of water
-Water is fine to come out and then but the net is(same amount going out as in)
-What we give in IV
Define hypotonic?
When there is a higher concentration inside the cell than outside, so water rushes in!
-Dangerous because can burst cells
Why does it take energy for the cell to be constantly moving ions in and out to maintain an ideal concentration?
Because disorder is energetically, favorable, to have order, we must use energy. If left to diffusion our cells would die.
What ions have a higher concentration inside the cell?
potassium (K+), hydrogen (H+)
What ions have a higher concentration outside the cell?
Sodium (Na +), magnesium (Mg 2+), calcium ( 2+), chlorine (cl-)
(Sam makes c c)
In what order will molecules diffuse through the membrane?
1: small and hydrophobic molecules (because bulk of membrane is hydrophobic, so they slide through)
2: small, uncharged, polar molecules ( can diffuse but not as well)
3: Large polar molecules (for example, sucrose. Too big, needs transporter to get through membrane.)
4: ions/charged molecules (cannot get through membrane and require ion transporter to get through)
What is passive transport?
When molecules go from a higher concentration down concentration gradient to a lower concentration
-Becomes less ordered
-Never requires energy (even if transport proteins are involved)
What is active transport?
When molecules move up from low concentration to high concentration
-Energy is always required, becoming more ordered
What are the three types of passive transport?
1: simple diffusion: for membrane permeable molecules that are small nonpolar and uncharged. No energy input, things pass easily through the lipid bilayer going from high concentration to low concentration
2: channel protein facilitated: protein helps with movement of a molecule through the membrane, open like a tunnel and very weekly and quickly interacts with the protein that goes through.
-Specific to what channels
-For things like water, that may be able to diffuse on its own, but needs help to go fast
3: transporter protein: slower than channel protein
-Undergoes series of confirmational changes to move the molecule from one side to the other (does not take energy in passive transport!)
Describe transporter-mediated diffusion in detail?
Moves the solute from the aqueous outer layer to the cytoplasmic side, via transporter protein, that undergoes multiple confirmation changes, including: outward – open, occluded, and inward – open.
-Goes from high concentration to low concentration (passive transport)
-Does not take energy
-solute interacts with transport protein well, the speed/rate of transport depends on how strongly the solute interacts with the transporter protein
Why is the rate of passive transport via transporter mediated diffusion initially faster than simple diffusion and channel mediated transport?
Because of the transporter affinity for solute, quickly grabs the solute, and starts going, but reaches Vmax, and cannot go any faster. Simple, diffusion, and channel, mediated transport, then surpass it, because they only have the limit of the entire bilayer.
What do enzyme kinetics dictate?
That the transporter protein Has to undergo confirmational change, and can only do that at a certain rate
What is the Vmax?
The fastest rate at which the enzyme/protein can do its job
What is the 1/2 Vmax?
An approximate affinity of how tightly that transporter binds to its transported molecules
-Gives info on how fast it works, is a half of the fastest rate it can do its job
-transporter mediated diffusion is higher at this point, because more interaction occurs with the solute 
What is the difference between transporter mediated diffusion being saturated, and channel mediated transport becoming “saturated?”
The transporter mediated diffusion becomes saturated When it’s reached the highest rate that it can undergo confirmational changes.
The channel mediated transport becomes saturated when so many of the solute are crowded that they have to tunnel through to get in through the bilayer
What are aquaporins?
Water channels
-Channel transporter, made for water(one solute for one channel)
-Water can diffuse, but not as quickly on its own
What is the shape of an aquaporin?
One water, molecule, wide, hydrogen bonding inside the channel, helps to pull the water molecules through
How does the glucose channel diffusion work?
(Review this card) Glucose leaves the bloodstream and enters the cell via passive transport after a meal, when there is high blood glucose
-This occurs because concentration outside cell is greater than inside because passive. The glucose goes through the transporter into the cell.
-The opposite would occur if blood sugar was low, the transporter doesn’t control it at all just lets them slide
Different types of the same transporter might have different Vmax values because?
The strength of the affinity of the interaction with its transport protein determines how strong that transporter grabs the solute it
-Higher affinity equals higher Vmax and ergo faster transportation rate
-For example GLUT3 in the brain has stronger Vmax than GLUT2 in the liver (grabs glucose)
Define active transport?
transporters “ pumping” salutes across the membrane against their concentration gradient
-Requires energy to move against the gradient
What are the three types of active transport pumps?
1: coupled transporter (for example, glucose – NA+ transporter)
2: ATP driven pump (for example, the sodium potassium pump, or the calcium pump) (most discussed in this class)
3: light driven pump (in bacteria, Arcia, and chloroplasts)
How do muscle cells use ATP to contract?
ATP is used for the relaxation after the contraction, when calcium must be pumped from inside the cell in the sarcoplasm to the SR through the SR lumen via active transport
