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Biology week 2-8-16

by: Audrey Notetaker

Biology week 2-8-16 200001

Marketplace > Boston College > Biology > 200001 > Biology week 2 8 16
Audrey Notetaker
GPA 3.9

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Chapter 6: Lipids, Membranes, and the First Cells
Molecules and Cells
Danielle Taghian
Class Notes
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This 4 page Class Notes was uploaded by Audrey Notetaker on Wednesday February 10, 2016. The Class Notes belongs to 200001 at Boston College taught by Danielle Taghian in Spring 2016. Since its upload, it has received 29 views. For similar materials see Molecules and Cells in Biology at Boston College.


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Date Created: 02/10/16
Chapter 6: Lipids, Membranes, and First Cells  2/8/16 Lipids and Membranes  Plasma membrane: protein containing lipid bilayer surrounding cells o Separates life inside vs outside of cell o Regulates the passage of molecules and ions into and out of the cell; selective  barrier   Hydrophobic/non polar molecules will pass more easily  Hydrophilic/polar/large molecules won't pass easily so proteins in the  membranes help facilitate them passing o Has a polar phosphate head and a non­polar fatty acid chain  How do membranes Help life o Enable different internal and external solutions o Help localize and bring together reactions that otherwise wouldn't occur; more  efficient also maximized o Localized specific functions  What is a lipid o Lipid: major hydrocarbon component which are normaly nonpolar and  hydrophobic; length varies and impacts the fluidity  Isoprene: hydrocarbon chain  5'C carbond  Fatty Acid: hydrocarbon chain bonded to a carboxyl group formed by  adding 2 carbon subunits  Carboxyl group is why it's called a fatty acid  Types of Lipids o Isoprene chains ­ have a methyl group sticking out  Steroids (chelesterol)  Amphipathic  Have a four ring structure made from isoprene subunits  Vary by different R groups  Cholesterol important in plasma membrane  Starting point for synthesis of estrogen, progesterone, and  testosterone  Phospholipid:   Glycerol group reacts with phosphate group has two isoprene  chains or two fatty acids   Amphipathic: has a hydrophilic (polar) head, and a hydrophobic  (nonpolar) tail o Fatty Acid ­ no methyl group  Fats  Fats formed from dehydration synthesis  Fats from glycerol linked by ester linkages to three fatty acids  Ester Linkage:   Phospholipid (serine)  Glycerol group + phosphate group o Most lipids have two chains o Phospholipase C can detach the phosphate head from the hydrocarbon component  Bonding/saturation o C double bond  Cis ­ has kinks in it, same side  Kinks help the fluidity of membrane  Trans ­ all hydrogens are on opposite side; not many kinks o Unsaturated/short: have double bonds (oil)  Permeable, liquid at room temperature o Saturated/long: max amount of hydrogens attached to carbon (butter)  Less permeable, solid at room temperature o Unsaturated lipids are better for membranes (better fluidity)  Membranes form spontaneously because of entropic forces (hydrophobic force) which is  the energy that causes the bilayer so nonpolar part is away from the polar water and polar head group is by water. The nonpolar acyl chains are then further stabilized by van der  Waals between the closely packed acyl chains (stronger forces with longer/larger  molecule)  Membrane formation o Liposome: bimolecular phospholipid layer with fluid filled inner cavity, like a  sphere o Micelle: single layer, all chains are in the middle with phosphate on the outside  (detergent); long single fatty acid chain; has a single fatty acid chain vs two o Bilayer:   Selective permeability o Permeability: tendency to let a substance cross  High to low permeability: hydrophobic, small uncharged, large uncharged, ions  Size and charge affect the rate of diffusion across membrane o Phospholipids have selective permeability  Small/nonpolar molecules move across quickly/easily without much if any help  Charged, large, or polar molecules cross slowly and need help (facilitated  transport) o Temperature affects membrane fluidity and permeability  Fluidity decreases with temperature because molecules move more slowly  Decrease membrane fluidity = decreased permeability ­ not  capable of supporting biochemical reactions  Fluidity: phospholipids are in constant lateral motion but rarely  flilp to the other side of the bilayer, movement laterally is fluidity


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