Chapter 12 Intro-12.1,.2

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Chapter 12 Intro-12.1,.2
2014-11-06 14:39:49
Test Three
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  1. ·         The boundaries of all cells are defined by __, which do what?
    o   __ also allow the cell to take up specific molecules and remove unwanted ones—called __
    ·         __components of the membrane form the barrier to permeability and __ act as transport systems of pumps and channels that allow selected molecules into and out of the cell
    • biological membranes
    • prevent molecules generated in the cell from leaking out and hindering things from diffusing in
    • Transport systems
    • selective permeability
    • Lipid 
    • proteins
  2. ·         Eukaryotic cells also have __, which have evolved to allow the __
    ·         Other functions: __ and __
    • internal membranes on organelles
    • targeting of selected proteins into or through particular internal membranes and into specific organelles
    • energy storage and info transduction
  3. • Common Features underlie the diversity of biological membranes

    First three.
    • o   Sheetlike structures: form closed boundaries between different compartments
    • o   Membranes consist of lipids and proteins: mass ratio of lipids to proteins ranges from 1:4 to 4:1; membranes also contain carbohydrates that are linked to lipids and proteins
    • o   Membrane lipids are small molecules that have both hydrophilic and hydrophobic moieties; they spontaneously form closed bimolecular sheets in aqueous media; these lipid bilayers are barriers to the flow of polar molecules
  4. • Common Features underlie the diversity of biological membranes

    • o   Specific proteins mediate distinctive functions of membranes: serve as pumps, channels, receptors, energy transducers, and enzymes; embedded in lipid bilayers, which create suitable environments for their actions
    • o   Membranes are noncovalent assemblies: held together by noncovalent interactions
    • o   Membranes are asymmetric
  5. • Common Features underlie the diversity of biological membranes

    • o   Membranes are fluid: lipid molecules diffuse rapidly in the plane of the membrane, as do proteins unless they are anchored by specific interactions; in contrast, lipid molecules and proteins do not readily rotate across the membranes; membranes can be regarded as 2D solutions of oriented proteins and lipids
    • o   Most cell membranes are electrically polarized
  6. ·         __ of lipids are essential to their ability to form membranes; most lipids owe their __properties to one component, their _, which are __
    ·         Fatty acids usually contain an __ of carbon atoms, around __, the most common being __
    • Hydrophobic properties
    • hydrophobic 
    • fatty acids
    • hydrocarbon chains of various lengths and degrees of unsaturation terminated with carboxylic acid groups
    • even number
    • 14 to 24
    • 16 to 18
  7. ·         The hydrocarbon chain is almost __; the alkyl chain may be __or it may contain __
    ·         Properties of fatty acids and lipids depend on __ and __
    o   Unsaturated fatty acids have __than do saturated fatty acids of the same length
    o   Chain length also affects __
    §  Short chain length and unsaturation enhance the __ of fatty acids and their derivatives
    • invariably unbranched in animal fatty acids
    • saturated 
    • one or more double bonds with a cis configuration
    • chain length and degree of saturation
    • lower MPs 
    • MP
    • fluidity
  8. ·         Lipids are __ that are highly __in organic solvents such as chloroform. Their roles include: __
    • water-insoluble biomolecules
    • soluble 
    • o   Serving as fuel molecules, highly concentrated energy stores, signal molecules, and messengers in signal-transduction pathways, and components of the membranes
  9. ·         The three major ones are __, __, and __
    ·         Phospholipids are composed of four components: __(4)__
    ·         The fatty acid components provide a __, whereas the remainder of the molecule has __ that enable __ 
    phospholipids, glycolipids, and cholesterol

    • one or more fatty acids, a platform to which the fatty acids are attached, a phosphate, and an alcohol attached to the phosphate
    • hydrophobic barrier
    • hydrophilic properties
    • interaction with the aqueous environment
  10. o   The platform on which phospholipids are built may be __, __, or __, a more complex alcohol
    §  Phospholipids derived from glycerol are called __, which consists of a __
    ·         In phosphoglycerides, the __ at C-1 and C-2 of glycerol are __to the __groups of the two fatty acid chains. The C-3 __group of the glycerol backbone is esterified to __
    • glycerol, a three-carbon alcohol, or sphingosine
    • phosphoglycerides
    • glycerol backbone to which are attached two fatty acid chains and a phosphorylated alcohol
    • hydroxyl groups
    • esterified 
    • carboxyl 
    • hydroxyl 
    • phosphoric acid
  11. o   When no further additions are made, the resulting compound is __, the simplest __. Only small amounts of __are preset in membranes, but it is a key intermediate in the __
    ·         The major phosphoglycerides are the __(5)__
    • phosphatidate
    • phosphoglyceride
    • phosphatidate 
    • biosynthesis of the other phosphoglycerides
    • amino acid serine, ethanolamine, choline, glycerol, and inositol
  12. ·         Sphingomyelin is a __
    o   Instead, the backbone in sphingomyelin is __, an __ that contains a long, unsaturated hydrocarbon chain
    §  In sphingomyelin, what?. In addition, what?
    • phospholipid found in membranes not derived from glycerol
    • sphingosine
    • amino alcohol

    the amino group of the sphingosine backbone is linked to a fatty acid by an amide bond

    the primary hydroxyl group of sphingosine is esterified to phosphorylcholine
  13. ·         Membrane lipids can include __
    ·         The second major class of membrane lipids, __, are sugar-containing lipids, which are derived from __
    o   The __ of the __backbone is __by a fatty acid. __differ from sphingomyelin in what? 
    • carbohydrate moieties
    • glycolipids
    • sphingosine
    • amino group
    • sphingosine 
    • acylated 
    • Glycolipids 
    • the identity of the unit that is linked to the primary hydroxyl group of the sphingosine backbone
  14. §  In glycolipids, one or more __are attached to this group
    ·         The simplest glycolipid, called a __, contains a __
    ·         More complex glycolipids, such as __, contain a __chain of as many as __.

    o   Glycolipids are oriented in a completely __ fashion with __.
    • sugars (rather than phosphorylcholine) 
    • cerebroside
    • single sugar residue, either glucose or galactose
    • gangliosides
    • branched
    • seven sugar residues
    • asymmetric 
    • the sugar residues always on the extracellular side of the membrane
  15. ·         __is a lipid based on a __ and is the third major type of membrane lipid. It is a __
    o   A __ is linked to the steroid at one end, and a __ is attached at the other end. IN membranes, the orientation of the molecule is __, and the hydroxyl group interacts with the __.
    o   Cholesterol is absent from __but is found to varying degrees in virtually all animal membranes. It constitutes almost __ in certain nerve cells but is essentially absent from some intracellular membranes 
    • Cholesterol 
    • steroid nucleus
    • steroid built from four linked hydrocarbons
    • hydrocarbon tail
    • hydroxyl group
    • parallel to the fatty acid chains of the phospholipids
    • nearby phospholipid head groups
    • prokaryotes 
    • 25% of the membrane lipids
  16. ·         Archaeal membranes are built from __
    o   The membranes of archaea differ in composition from those of eukaryotes of bacteria in three important ways. What are they?
    ether lipids with branched chains

    § First, the nonpolar chains are joined to a glycerol backbone by ether rather than ester linkages, which is more resistant to hydrolysis
  17. What s the second important way?
    § Second, the alkyl chains are branched rather than linear and are built up from repeats of a fully saturated five-carbon fragment, making them more resistant to oxidation, which helps archaea withstand the extreme conditions
  18. What s the third important way?
    § Finally, the stereochemistry of the central glycerol is inverted
  19. ·         Membrane lipids are __molecules, containing both __ and __.
    o   The hydrophobic fatty acids are __, while the hydrophilic part faces the __
    • amphipathic 
    • hydrophilic and hydrophobic moieties
    • parallel to each other
    • opposite direction (polar head group)