Lipids

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Lipids

• Highly diverse structures
• Unifying property
• Hydrophobic little to no affinity to water
• Contains hydrocarbons, which form nonpolar
  covalent bonds
• Do not form polymers
• Biologically important lipids containing
  molecules
• Fats
• Phospholipids
• Steroids

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Fats

• Structure
• Composed of two different molecules bonded by
  ester linkage
• fatty acid glycerol
• - Fatty acid
• Hydrocarbon chain with a carboxyl group at
  one end
• Glycerol
• Three-carbon alcohol
• Each carbon attached to hydroxyl group

Try to Draw
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LE 5-11a
Fatty acid (palmitic acid)
Glycerol
Dehydration reaction in the synthesis of a fat
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LE 5-11b
Ester linkage
Fat molecule (triacylglycerol)
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Properties of Fats

• Hydrophobic
• H2O molecules form hydrogen bonds with each other
  and EXCLUDE fatty acid chains--gt
• Fats separate from H2O (like oil vinegar)

Fatty acids variable chain length (often 16-18
carbons)
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Saturated fat - refers to saturated fatty acid
chains - carbons contains maximum number of
hydrogens - results in 100 single bonds (no
double bonds) - more linear, packs
tightly to form solid Tend to be from animals
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LE 5-11b
Saturated or unsaturated?
Ester linkage
Fat molecule (triacylglycerol)
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LE 5-12a
Butter
Stearic acid
Saturated fat and fatty acid.
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Unsaturated fat -contains unsaturated fatty
acids -carbon-carbon double bonds
(gt1) -irregular hydrocarbon conformation -poor
packing -forms liquids (oils) at room
temperature Tend to be from plants and fish
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LE 5-12b
Olive oil
Other liquid fats (unsaturated)?
Oleic acid
cis double bond causes bending
Unsaturated fat and fatty acid.
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Phospholipids

• Structure
• two fatty acids bonded to glycerol through ester
  linkage
• Phosphate bonded to third hydroxyl group of
  glycerol
• Fatty acids Hydrophobic tail
• Phosphate and other groups hydrophilic head

Draw schematic
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LE 5-13
Choline
Hydrophilic head
Phosphate
Glycerol
Hydrophobic tails
Fatty acids
Hydrophilic head
Hydrophobic tails
Structural formula
Space-filling model
Phospholipid symbol
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If many phospholipids were mixed in H2O into
what structures would they self-assemble?

• Micelle (draw)
• - Detergents
• Bilayer (draw)
• -Cell membranes

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LE 5-14
Cellular membrane Phospholipid Bilayer
WATER
Hydrophilic head
Hydrophobic tails
WATER
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Steroids

• Structure
• - Hydrophobic molecules made of 4 fused
  hydrocarbon rings
• Examples and Diverse Functions
• Cholesterol
• Component of animal cell membranes
• Building block for steroid sex hormones such as
• Estrogen, testosterone, progesterone
• High levels--gt contribute to heart disease

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Cholesterol
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estradiol
testosterone
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Pardon me. Did you miss anything?