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Lipids in General Biology

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Terms in this set (20)

  • What are the four main classes of lipids?
    Triglycerides, Phospholipids, Steroids, and Waxes.
  • What is the basic structure of a triglyceride?
    Three fatty acids bonded to one glycerol molecule via ester linkages.
  • What functional group characterizes fatty acids?
    A carboxyl group (-COOH), which is polar.
  • Difference between saturated and unsaturated fatty acids?
    Saturated fatty acids lack C=C bonds and are solid at room temperature; unsaturated fatty acids have at least one C=C bond.
  • Why are triglycerides nonpolar despite containing polar groups?
    Dehydration synthesis forms ester linkages, removing polar -OH and -COOH groups, leaving a nonpolar molecule.
  • What is glycerol chemically?
    An alcohol with three hydroxyl (-OH) groups, making it polar and hydrophilic.
  • What makes phospholipids amphipathic?
    They have a hydrophilic phosphate head and two hydrophobic fatty acid tails.
  • How do phospholipids arrange in cell membranes?
    In a bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward toward water.
  • What linkages are found in phospholipids but not in triglycerides?
    Phospholipids have phosphoester linkages in addition to ester linkages; triglycerides have only ester linkages.
  • What is the general empirical formula for saturated fatty acids?
    \(C_xH_{2x}O_2\).
  • How does the empirical formula change for monounsaturated fatty acids?
    It becomes \(C_xH_{2x-2}O_2\) due to loss of two hydrogens from one C=C bond.
  • Give an example of a saturated fatty acid and its carbon length.
    Stearic acid, a C18 saturated fatty acid.
  • Give an example of a monounsaturated fatty acid and its carbon length.
    Oleic acid, a C18 monounsaturated fatty acid.
  • What is the structure of steroids compared to other lipids?
    Steroids have a four-ring structure and lack fatty acids, glycerol, ester, or phosphoester linkages.
  • Name some examples of steroids.
    Cholesterol, estrogen, progesterone, and testosterone.
  • What are waxes composed of?
    One saturated fatty acid and one long-chain alcohol (not glycerol).
  • Why is acetic acid considered a short-chain fatty acid (SCFA)?
    It has two carbons and is produced by microbial fermentation in the gut, playing a role in energy metabolism.
  • Why is acetic acid more water-soluble than longer fatty acids?
    Because of its short carbon chain and polar carboxyl group, making it hydrophilic.
  • What is the role of the choline group in phospholipids?
    It is part of the phosphate head, contributing to the hydrophilic nature of the phospholipid.
  • How many ester linkages are in a triglyceride versus a phospholipid?
    Triglycerides have three ester linkages; phospholipids have two ester linkages and one phosphoester linkage.