SL+D103+lecture+3

SL+D103+lecture+3 - D103: Cell Biology Dr. Shin Lin Lecture...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
D103: Cell Biology Dr. Shin Lin
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Lecture 3 Biological Membranes II: Transport Functions (Diffusion, Transporters, Pumps) Recommended Reading: MBOC (5th edition) 651-667
Background image of page 2
iClicker: The mammalian cell membrane has the following permeability property: • A. Foreign DNA, large or small, can NEVER getting into the cell from the outside. • B. Building blocks of DNA, i.e., nucleotides, can NEVER get because they are charged molecules. • C. Glucose is uncharged so it can readily get into the cell. D103 Fall 2011 Lecture 3 © Lin All rights reserved
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
D103 Fall 2011 Lecture 3 © Lin All rights reserved A lipid bilayer is a semi-permeability barrier Transport of small molecules across the membrane is by simple diffusion Transport of large uncharged polar molecules and ions across the lipid bilayer requires membrane transport proteins
Background image of page 4
D103 Fall 2011 Lecture 3 © Lin All rights reserved Simple (Passive) Diffusion http://www.northland. cc.mn.us/biology/BIO LOGY1111/animation s/active1.swf
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
D103 Fall 2011 Lecture 3 © Lin All rights reserved Passive Diffusion Across Membrane (Fisk’s Law)
Background image of page 6
D103 Fall 2011 Lecture 3 © Lin All rights reserved KEY CONCEPTS Selective transport across the lipid membrane requires transport proteins to increase the rate in addition simple diffusion as predicted by Fisk’s Law (particularly against concentration gradient) • Transport proteins are integral membrane proteins that move molecules and ions • There are two classes of transport proteins: transporters and channels 7
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
D103 Fall 2011 Lecture 3 © Lin All rights reserved Two Main Classes of Membrane Transport Proteins Transporters (also called carriers) Bind specific solute Undergo conformational changes to transfer bound solute Channels Form aqueous pores Open to allow specific ions to pass through 8 http://www.northland.cc.mn.us/biology/BIOLOGY1111/animations/active1.swf
Background image of page 8
D103 Fall 2011 Lecture 3 © Lin All rights reserved Membrane Transport Proteins Common features: are transmembrane proteins that contain multiple membrane-spanning segments (α helices) form protein-lined pathway across lipid layer , allowing water-soluble molecules to pass without contacting hydrophobic core of membrane • undergo conformational changes 9
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
D103 Fall 2011 Lecture 3 © Lin All rights reserved Membrane Transport Proteins Differences: 1. Transporters Uniporters transport a single solute down its gradient Symporters and antiporters couple movement of a solute (an ion) with movement of another solute (cotransport) 2. Pumps : move solutes up concentration gradient using energy derived from ATP hydrolysis 3. Channels: allow solutes to pass through pores down their concentration gradients 10
Background image of page 10
D103 Fall 2011 Lecture 3 © Lin All rights reserved How does a transporter work? Transporters – have one (or more) specific binding site for solute – undergo rounds of reversible conformation changes conformational changes alternately expose the solute-binding site first on the outside (state A) of the membrane and then the inside (state B) – transport rate:10 2 -10 4 /s (slow!) 11
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 46

SL+D103+lecture+3 - D103: Cell Biology Dr. Shin Lin Lecture...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online