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Biology 1002 Membrane Function.pdf

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Western University
Biology 1002B
Tom Haffie

Lecture 5: Membrane Function Jan 22, 2013 • lipid bilayer happen spontaneous because of the hydrohphobic tendency • lipids can be saturated or unsaturated fatty acid (tail of phospholipid) • saturated with Hydrogens • importance of saturation is sites of unsaturation cause a kink in the fatty acid changing the packaging style fatty acids that are saturated are packed closely together causing a less fluid • membrane • fatty acids that are unsaturated are not packed closely together and depending on how many kinks the more fluid Lecture 5: Membrane Function Jan 22, 2013 • desaturase increases unsaturation at low temperatures= the organism is trying to compensate for gelling at low temps and increases permeability • Desaturase puts the carbon-carbon double bond in the fatty acid • cells that cannot control their temp can control desaturase fatty acids are hydrophobic • • small and uncharged you get right through the membrane • if your large and have a charge its not as easy • charge and size determine permeability • oxygen and such ions just diffuse across • bigger molecules like glucose need to be transported across the membrane via transport protein Lecture 5: Membrane Function Jan 22, 2013 • hydrophilic inside Membrane Protein • have several alpha helices, hydrogen bonding minimizes charges in backbones enabling the protein to interact • the nonpolar amino acids are hydrophobic • the polar and charged amino acids are hydrophilic Lecture 5: Membrane Function Jan 22, 2013 From a primary structure you cannot predict where an enzyme activation site is because it will interact with its substrate and must still fold. • small molecules diffuse by themselves bigger molecules like glucoses are gotten thru the membrane by facilitated diffusion • (pores are specified and it is was one molecule at the time) • active transport (pumping against the transport gradient) ▯ -uses ATP energy Modeling a Neuron • ions diffuse along electrochemical gradients (ions have charges)
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