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From Chapters 8 & 9 (LIPIDS and MEMBRANES) and related lecture material you shouldKnow 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 membraneso 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 tailso Fatty acidso Triacylglycerolso Phosphoacylglycerolso Sphingolipidso Eicosanoidso Waxes- Fused ring compoundso Steroidso 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- Saturatedo No double bonds- Unsaturatedo Double bonds Mono-unsaturated (1) Poly-unsaturated (2 or more)o Trans-fat: rigidifies the hydrocarbon tail in extended conformationo Cis-bond: causes a bend in the hydrocarbon tail - Melting pointo Increases with increases chain lengtho 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)- Glycerolo- Triglycerideso Major components of fats and oilso Main way to store chemical energy for long termo 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 kJouleo White fat – nutrient storage, thermoinsulationo Brown fat – energy burning adipose tissue rich in mitochondria – produce heato Omega-3 fatty acids Decrease the risk of arrhythmias Decrease triglyeride levels Slow the growth rate of atherosclerotic plaque Lower blood pressureo 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 bloodKnow the general structure of phospholipids, and their structural and functional role in the makeup of cell membranes- Major membrane components- Know red, recognize blueKnow 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 transportKnow 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 organismsUnderstand 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 thefused 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, autophagosomeo Lipid (and protein) composition of these membranes differs Properties of Biological membranes:o Form spontaneously without the input of extra energyo Self-sealing:  Small lesions can be healed by lateral diffusion of lipids Larger lesions are healed by a regulated fusion with intracellular vesicleso Semi-permeable:  Permeable for nonpolar compounds, but virtually impermeable for polar substanceso Asymmetric:  Composition of membrane leaflets differs substantiallyKnow the general properties of a‐helices and b‐ sheets that allow proteins to span biological membranes- A-heliceso Hydrophobic portion of membrane: 30 Ao 3.6 residues per turno Pitch of 5.4 A- B-sheetso Exterior residues interact with the membrane, and are hydrophobico Interior residues (lining the pore) are polaro A minimum of 8 b-strands are necessary to form a membrane spanning b-barrelo Large b-barrel proteins may contain a hydrophilic pore Hydropathy plot is typically less characteristic than that of alpha helical transmembrane proteinsUnderstand the differences between simple diffusion (across biological membranes) and facilitated diffusion as well as between active and passive transport- Simple diffusiono A substance moves directly through the membrane (limited to hydrophobic and small uncharged molecules, gases (CO2, O2))- Facilitated diffusiono A substance moves through the membrane with the aid of a protein – channel(pores in

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OSU BIOCHEM 4511 - Chapter 8

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