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Lecture 5

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Biology 1002B
Tom Haffie

Biology 1002B Lecture 5 – Lecture Notes Membrane Biology - Bilayers form spontaneously because of hydrophobic tails. - The left tail is saturated while right tail is unsaturated in the picture above. - Can have many sites of unsaturation (carbon-carbon double bonds) - Lots of unsaturated, more fluidity. - Lots of saturated and packed tightly, less fluidity. Importance of unsaturation: - Saturated, linear molecules are acted on by desaturase. - Manipulating desaturase abundance can help manage membrane fluidity. - Many desaturase enzymes, because some will want a little unsaturation and some may want a lot of saturation. Some desaturases could work at different temperatures. **Enzymes differ in where the double bond will take place. Membrane Permeability: - if small and uncharged, easy to get through, large and very charged, hard to get through. - Nonpolar molecules just diffuse down concentration gradient. - Ions need to be transported across because they can’t readily diffuse across. - Membrane proteins transport molecules across membranes. - Many alphahelises minimizes the charges of the protein backbone. So it can interact with hydrophobic s acid tails. - Membrane proteins have tell-tail signature of where active site is, nonpolar, uncharged amino acids at active site. Membrane Transport: - Diffusion down a concentration gradient, less of the molecule. Driven by free energy change. More ability to do work when there are more molecule on one side than the other. - Facilitating diffusion: using protein pore or channel allowing lots of molecule to transport through membrane. Some pores only allow one at a time. Channel allows much more molecules. - Active transport: pumping things against concentration gradient. Moving molecule from low concentration to higher concentration. Against free energy change, need energy to do this. ABC transporters (group of molecules) are active transporters. - Different transporters transport different things. Modeling a neuron: - Ions diffuse along electrochemical gradients. - Not just chemical (how much of each on both sides of membrane) but electrical (what charge on each side). - Equilibrium doesn’t mean same concentration of molecu
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