8.3 Membrane Transport [HY] Flashcards
1
Q
How do small and large molecules go through cell membrane?
A
Transport of small nonpolar molecules occurs rapidly through the cell membrane via diffusion, while ions and larger molecules require more specialized transport processes.
2
Q
What type of transport increases with temp?
A
- Diffusion, facilitated diffusion, and osmosis. Increase as temp. increases
3
Q
Is active transport affected by temperature?
A
- active transport may or may not be affected by temperature, depending on the enthalpy (ΔH) of the process
4
Q
What affects passive transport thermodynamically?
A
- an increase in entropy (ΔS)
5
Q
Simple diffusion
A
- The most basic of all membrane traffic processes
- substrates move down their concentration gradient directly across the membrane
- Only particles that are freely
permeable to the membrane are able to undergo simple diffusion
6
Q
Osmosis
A
- Water concentration moves down gradient from high to low
- Water solute concentration moves up gradient from low to high
7
Q
Hypotonic
A
- If the concentration of solutes inside the cell is higher than the surrounding solution
- such a solution will cause a cell to swell as water rushes in, sometimes to the point of bursting (lysing).
8
Q
Hypertonic
A
- A solution that is more concentrated than the cell
- water will move out of the cell
9
Q
Isotonic
A
- If the solutions inside and outside are equimolar
- prevents the net movement of particles
10
Q
Osmotic pressure
A
- a colligative property
- a physical property of solutions that is dependent on the concentration of dissolved particles
- II= iMRT [M is molarity. R is gas constant. i is van’t hoff factor, T is absolute temp.
- If the osmotic pressure created by the solutes within a cell exceeds the pressure that the cell membrane can withstand, the cell will lyse.
11
Q
What does osmotic pressure formula tell us?
A
- directly proportional to the molarity of the solution
- osmotic pressure,
like all colligative properties, depends only on the presence and number of particles in solution, but not their actual identity.
12
Q
Semipermeable membrane
A
- refers to a membrane governed by the same permeability rules as biological membranes: small, nonpolar, lipid-soluble particles (and water) can pass through freely, while large, polar, or charged particles cannot
13
Q
Facilitated Diffusion
A
- simple diffusion for molecules that are impermeable to the membrane (large, polar, or charged)
- requires integral membrane proteins to serve as transporters or channels for these substrates.
- Channels are also viable for facilitated diffusion
14
Q
Occluded state
A
- When the carrier is not open to either side of the phospholipid bilayer
- Binding of the substrate molecule to the transporter protein induces a conformational change and the carrier is briefly in this state
15
Q
How do channels in an open conformation work?
A
- exposed to both sides of the cell membrane and act like a tunnel for the particles to diffuse through, thereby permitting much more rapid transport kinetics.
