From Chapters 8 9 LIPIDS and MEMBRANES and related lecture material you should Know the general definition features and functions of lipids in the cell Lipids a heterogeneous class of organic molecules with marginal solubility in water hydrophobic Functions o Biological membranes o Energy storage triglycerides o Electrical insulation impermeable for ions o Thermal insulation adipose tissue o Hydro insulation water repelling waxes o Signaling cholesterol phosphatidylinositol phosphoinositides o Hormone and vitamin precursors steroids vitamins D E K A o Digestion bile acids Know the two major kinds of cellular lipids straight chain and fused rings and the subclasses that we discussed in class Straight chain open chain polar head groups with long non polar aliphatic tails o Fatty acids o Triacylglycerols o Phosphoacylglycerols o Sphingolipids o Eicosanoids o Waxes Fused ring compounds o Steroids o Lipid vitamins all are isoprenoids Know the general structure of fatty acids how fatty acids are named both formally and informally including the common names of fatty acids listed in the lecture notes Hydrocarbon chain with carboxyl group at end Understand the difference in properties of saturated and unsaturated fatty acids including the contribution to melting point of chain length and cis double bonds Saturated o No double bonds Unsaturated o Double bonds Mono unsaturated 1 Poly unsaturated 2 or more o Trans fat rigidifies the hydrocarbon tail in extended conformation o Cis bond causes a bend in the hydrocarbon tail Melting point o Increases with increases chain length o Decreases more dramatically with degree of unsaturation Know the general structure of glycerol and of a triglyceride and know the function of triglycerides in energy storage and thermal insulation inside cells and bodies Glycerol o Triglycerides o Major components of fats and oils o Main way to store chemical energy for long term o Fatty acids have 2 2 times higher energetic value per weight compared to carbohydrates Because energy is gained by oxidation of organic molecules Fatty acids are less oxidized 1 kcal 1 Cal food or large calorie 4 2 kJoule o White fat nutrient storage thermoinsulation o Brown fat energy burning adipose tissue rich in mitochondria produce heat o Omega 3 fatty acids Decrease the risk of arrhythmias Decrease triglyeride levels Lower blood pressure Slow the growth rate of atherosclerotic plaque o w6 and w3 fatty acids are essential w6 promote inflammation w3 anti inflammatory Healthy ratio of w6 w3 1 1 1 4 Lower cholesterol in blood Know the general structure of phospholipids and their structural and functional role in the makeup of cell membranes Major membrane components Know red recognize blue Know the structure of the common phosphatidyl linked polar head groups serine glycerol ethanolamine choline Above Phosphatidyl serine PS negatively charged a major constituent of the cytosolic inner side of cell membranes In apoptosis PS gets translocated to the outer learlet to trigger cell phagocytosis Phosphatidyl inositol PI negatively charged a minor constituent of the cytosolic side of cell membrane Involved in signaling Can be phosphorylated at multiple positions of inositol hydroxyls signaling membrane trafficking Phosphatidyl ethanolamine PE in membranes of all living cells primary phospholipids in bacteria high in brain Phosphatidyl choline PC a major constituent of membranes Cardiolipin inner mitochondrial membrane involved in regulation of proton transport Know the four classes of phospholipases including the selective bonds they hydrolyze Understand the general structure of a wax ester and the common functions of waxes in living organisms Understand the general structure of sphingolipids including the structure of sphingosine Sphingosine dialcohol instead of glycerol Be able to recognize general structure of eicosanoids and know the fact that they play a role in inflammation and immune response Know the three functions of cholesterol in the animal cell membrane and be able to recognize the fused ring structure of cholesterol or closely related derivatives as steroids Essential component of mammalian but not prokaryotic cell membranes establishes proper fluidity and permeability Precursor of steroid hormones bile acids and vitamin D Excessive accumulation of cholesterol in arterial walls results in arteriosclerosis thrombosis heart attacks and strokes Understand the general structure and function of biological membranes fluid mosaic model including early experiments discussed in class that validated this model Biological membranes are non covalent assemblies of lipids and proteins that form boundaries of cells and organelles Lipids are major constituents of all cellular membranes o Cytoplasmic nuclear ER Golgi endosome lysosome peroxisome mitochondrion autophagosome o Lipid and protein composition of these membranes differs Properties of Biological membranes without the input of extra energy o Form spontaneously o Self sealing Larger lesions are healed by a regulated fusion with intracellular vesicles Small lesions can be healed by lateral diffusion of lipids o Semi permeable Permeable for nonpolar compounds but virtually impermeable for polar substances o Asymmetric Composition of membrane leaflets differs substantially Know the general properties of a helices and b sheets that allow proteins to span biological membranes A helices B sheets o Hydrophobic portion of membrane 30 A o 3 6 residues per turn o Pitch of 5 4 A o Exterior residues interact with the membrane and are hydrophobic o Interior residues lining the pore are polar o A minimum of 8 b strands are necessary to form a membrane spanning b barrel o Large b barrel proteins may contain a hydrophilic pore Hydropathy plot is typically less characteristic than that of alpha helical transmembrane proteins Understand the differences between simple diffusion across biological membranes and facilitated diffusion as well as between active and passive transport Simple diffusion Facilitated diffusion o A substance moves directly through the membrane limited to hydrophobic and small uncharged molecules gases CO2 O2 o A substance moves through the membrane with the aid of a protein channel pores in bacteria or a carrier Uniport Antiport Symport Know the difference between the three types of facilitated transport uniport antiport symport o Moves one substance at a time o Moves two different substances in opposite directions across the membrane o