L04-2011 Memb2 - Lecture4 Fourgroupsofmacromoleculesincells

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Lecture 4 Lipids/Fats/Membranes Begin Proteins Four groups of macromolecules in cells
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Small organic molecules are the building blocks of biological  macromolecules Building blocks Larger unit (polymer) Fatty acids Fats/lipids/Membranes Sugars Polysaccharides Amino acids Proteins Nucleotides Nucleic acids ECB 2-15 Fats/Lipids - Only group that is not a polymer of subunits
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Most lipids are in membran Plasma membrane Various organelle  membranes Where is the site of lipid  biosynthesis? ECB 1-24 Animal or plant  cell? Membranes act as selective barriers; Plasma membrane is barrier between the cytoplasm and extracellular environment Functions in; Import and export Cell motility Cell signaling Membranes are also barriers between organelles and the cytoplasm in eukaryotes
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Lipids/Fats/Membranes Fatty Acids Phospholipids Lipid bilayer Proteins Amino Acids Peptide bond Other membrane lipids Membrane properties - fluidity Lecture 4
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Hydrophilic  Carboxylic acid  head group Amphipathic - hydrophilic and hydrophobic regions Fatty Acids Hydrophobic  hydrocarbon  tail (14 to 22C long) ECB 2-18
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Fatty acids are distinguished by chain length and double bonds Stearic acid 18 carbons, saturated Saturated = no double bonds in hydrocarbon tail (C is saturated with bonds to H) Common in fats, solid at room T Raise cholesterol levels Unsaturated = contains 1 or  more double bonds amphipathic (but fatty acids are not soluble in water) ECB Panel 2-4 Chain – 14 – 22 C long
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Unsaturated fatty acids contain 1 or more double bonds in  tail C H H C R R C H H C R R Unsaturated 1 double bond    (common in oils) Cis or trans? Oleic Acid 18 carbons Diet Trans – bad, not easily degraded;  coronary heart  disease Cis - good Cis double bond puts kink in chain trans cis
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Triacyl Glycerol  = 3 fatty acids bonded to  glycerol (Ester bond - carboxylic acid and alcohol) Energy storage fats (meat, butter, cream) oils (olive oil, corn oil) More efficient way to store energy than glycogen Most lipids in cells are formed by covalent bonds  between fatty acids and glycerol Hydrophobic ECB 11-10 (Lipids are not just polymers of fatty acids) Phospholipids are similar except one fatty acid replaced by phosphate and polar head group  Phospholipid CH 2 OH CH OH CH 2 OH Glycerol (glycerin)
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Phospholipid - 3 parts Major component of membranes Hydrophobic tails= fatty  acid side chains glycerol Polar Head Group = phosphate + polar group (Variable, 6-8 common ones) Named after polar head group: Phosphatidyl choline (most abundant p.l. in cell  membranes) Amphipathic   - Hydrophobic and  hydrophilic domains  ECB 11-6
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L04-2011 Memb2 - Lecture4 Fourgroupsofmacromoleculesincells

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