Exam Review Notes

lOMoARcPSD|4400775




Exam 1 Lecture 3


Animal Physiology (Louisiana Tech University)




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Lecture 3
● J=DA ( C −C
1
X )
2



● J = rate of diffusion
● D = diffusion coefficient: depends on temperature, lipid solubility, and size of solute
o Lipid solubility: depends on polarity
o Increase D → increase J
● A = surface area for diffusion
● Purpose: Used to determine the polarity

1. What materials can diffuse directly through a cell membrane? Why can they diffuse through?
● Selectively permeable: allow certain molecules to pass through but not others
o Lipid solubility (charge) is the most important
o Size
● Movement across a membrane
o Passive: requires no energy input
o Active: requires energy
● Passive transport moves a substance from high → low concentration
● Methods of passive transport:
o Simple diffusion
o Facilitated transport
▪ Passive diffusion
▪ Facilitated diffusion
o Osmosis
● Diffusion directly across lipid bilayer (simple diffusion):
o Lipid soluble (non-polar)
o Small: O2, CO2
o Ions cannot easily pass through because they are charged
2. Describe the components of Fick’s Law of Diffusion and explain how they affect diffusion
rates.
● Fick’s Law: rate of diffusion across membranes J=DA 1
C −C 2
X ( )
●
o Increase A → increase J
● C1 = high concentration
o Increase C1 → increase J
● C2 = low concentration
o Increase C2 → decrease J
● X = distance separating areas of high and low concentration
o Increase X → decrease J
● ∆C = concentration gradient of substance
o Increase ∆C → increase J
β
● D∝
√❑

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