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MU - BIO 203 - Bio 203 James Week 6 - Class Notes

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MU - BIO 203 - Bio 203 James Week 6 - Class Notes

School: Miami University
Department: Biology
Course: Cell Biology
Professor: James
Term: Fall 2018
Tags: cellular biology
Name: Bio 203 James Week 6
Description: transporters, channeles, gradients, membrane potentials, glucose transport
Uploaded: 10/04/2018
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background image BIO 203 James 9/27 (No class Tuesday, Quiz on Thursday)
 CHAPTER 12 MEMBRANE TRANSPORT
A. Diffusion Across Lipid Bilayer a. Diffusion- net movement of particles from area of high  concentration to low concentration b. Small nonpolar molecules (O2, CO2, N2, steroids) c. Small uncharged polar molecules (H2O, ethanol, glycerol) i. Depends on size, smaller the molecule the more likely it 
can diffuse
d. Larger uncharged polar molecules (amino acids, glucose,  nucleotides) i. Cannot diffuse e. Ions (H+, Na+, Cl-, Mg2+, HCO3-) i. Really cannot diffuse B. Partition coefficient a. Measure of hydrophobicity
b. Experimentally determined
c. Ratio of concentrations in a two-phase system at equilibrium
d. Higher value is more lipid soluble and more hydrophobic
C. Concentration gradients, membrane potentials, and electrochemical  gradient a. Take energy to establish
b. Free energy stored in gradient
c. Free energy released when molecule moves down gradient
d. Amount free energy released depends on magnitude of gradient
D. Electrochemical gradient: concentration gradient + membrane  potential  a. Electrochemical gradient can be influenced by membrane  potential b. If charge works against gradient, less diffusion
c. If charge works with gradient, more diffusion 
E. Membrane Transport Proteins: Transporters and Channels a. Transporters have binding site and is specific i. Undergoes conformation change b. Simple diffusion across biomembranes i. No specific transporter involved ii. Movement occurs throughout face of membrane iii. Initial rate only dependent on solute concentration iv. Linear plot c. Facilitated transport i. Saturable ii. Specific transporter involved iii. Transporter iv. Each transporter has maximal transport rate v. Curve line that levels off F. Passive and Active Transport
background image a. Passive transport- energy stored in gradient i. Simple diffusion ii. Channel-mediated iii. Transported-mediated b. Active transport- additional input of energy not present in  concentration gradient i. Against electrochemical gradient ii. Against concentration gradient (low concentration to high  concentration) iii. Coupled pump: one solute moves down electrochemical  gradient and releases energy that is used to move another 
solute against the gradient
1. Secondary active transport (uses gradient  established by other ions/solutes for energy) iv. ATP driven pump 1. Primary active transport (hydrolyzes ATP for energy) v. Light-driven pump G. Transporters a. Uniport (passive) i. Moves sugar ii. Substrate moves down concentration gradient (no  electrochemical gradient because sugar has no charge) iii. Protein changes from binding side accessible on  extracellular side to occluded stage (not accessible from
either side) to being accessible on cytosolic side 
(conformational change)
b. Active coupled transporters i. Symport- Solutes moved in same direction ii. Antiport- solutes moved in opposite directions c. ATP driven pumps i. P type (plasma membrane and intracellular membrane) 1. Example: Sodium-potassium/ATPase
2. Each ATP hydrolyzed= 3 Na+ out of cell and 2 K+ 
into cell 3. Important for maintain osmotic balance ii. V type  1. Are usually pumps
2. Moves only protons
3. From inside a cell to inside a vesicle or vacuole
iii. F type  1. Usually uses proton gradient established in a  different way 2. only protons iv. ABC transporter H. Glucose transport a. Gut lumen (low Glu)

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School: Miami University
Department: Biology
Course: Cell Biology
Professor: James
Term: Fall 2018
Tags: cellular biology
Name: Bio 203 James Week 6
Description: transporters, channeles, gradients, membrane potentials, glucose transport
Uploaded: 10/04/2018
3 Pages 31 Views 24 Unlocks
  • Better Grades Guarantee
  • 24/7 Homework help
  • Notes, Study Guides, Flashcards + More!
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