Lipids

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Lipids
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Lipids

• Like Carbohydrates are composed of the elements
  C, H, O
• The ratio of oxygen to carbon is extremely small
  (O/C ltltlt 1)
• There is almost no oxygen in relation to the rest
  of the molecule
• Therefore they are essentially hydrocarbons (C, H)

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Polarity and solubility

• The C-H covalent bond of lipids are non-polar
• So following the rule of like dissolves like
• Lipids are soluble in non-polar solvents such as
  chloroform or ether
• And are insoluble in water the are hydrophobic
  ( water fearing or hating)

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Some functions of lipids

• Energy storage (long term)
• Heat insulators
• Nerve insulators
• Lubricant for joints (synovial fluid)
• Hormones (sex hormones such as testosterone and
  estrogen)
• Membranes of cells
• Protection against water loss (ex. waxes in
  plants)

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Types of Lipids (well look at!)

• Fatty Acids (saturated and unsaturated)
• Fats (especially triglycerides)
• Phospholipids
• Steroids

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Fatty Acids

• Long chain hydrocarbons with a carboxylic acid
  group at one end
• of C is usually 12-20.

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Saturated Fatty Acid

• Contains the maximum possible number of hydrogen
  atoms
• Therefore there are no double bonds in the chain.

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Unsaturated Fatty Acids

• Contains one or more double bonds between carbons
• Therefore is NOT carrying the maximum possible
  number of H atoms
• Monounsaturated fatty acid contains only one
  double bond
• Polyunsaturated fatty acid contains more than one
  double bond.

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(c)

• is a saturated fatty acid (F.A.)
• is a monounsaturated F.A.
• is a polyunsaturated F.A.

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Saturated vs. Unsaturated
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Essential Fatty Acids

• Can't make ourselves, but we must have for normal
  function (in diet from plants)
• Examples
• Linoleic (182)
• Look in packet of structures
• for diagram
• Achidonic acid (204)
• (Number of Carbons Number
• of double bonds)

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Arachidonic acid
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Neutral Fats

• Glycerol 1-3 fatty acids
• Triglyceride has 3 fatty acids
• What is a monoglyceride?
• What is a diglyceride?
• AGAIN refer to your packet of structures!

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Formation of a Monoglyceride
CONDENSATION REACTION!!
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A Triglyceride
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What is an unsaturated neutral fat?

• A fat molecule containing one or more unsaturated
  fatty acids
• The diagram on the previous slide would be a
  saturated neutral fat
• Right is an unsaturated neutral fat

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Saturated vs. Unsaturated

• Saturated fats are mostly animal fats and are
  solid at room temperature
• Diets high in these fats can result in clogged
  arteries cholesterol will line the blood
  vessels and restrict blood flow
• Unsaturated fats are mostly from plants and fish
  and are liquids at room temperature
• These are oils due to the kinks in their
  hydrocarbon chains not allowing them to pack
  closely together.

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Back to hydrolysis and condensation

• So if a triglyceride is formed from a glycerol
  and 3 fatty acids by a CONDENSATION REACTION
• what would we get if we were to HYDROLYZE a
  triglyceride?
• A glycerol 3 Fatty Acids

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Back to hydrolysis and condensation

• Glycerol 3 Fatty Acids ? Triglyceride H2O
• Condensation reaction
• Triglyceride H2O ? Glycerol 3 Fatty Acids
• Hydrolysis reaction

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Phospholipids
ion

• Membrane lipids
• Composed of
• Glycerol
• 2 fatty acids
• a phosphate group
• an ion ( or -)

phosphate
glycerol
2 fatty acids
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Phospholipids

• Phospholipids are Amphipathic
• One end is hydrophilic
• One end is hydrophobic
• This unique structure makes them suitable to form
  cell membranes!
• They form micelles or bilayers see next slide!

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Membrane formation by phospholipids
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Steroids

• Contain four rings of Carbon atoms
• Sterols have an alcohol group (a.k.a. hydroxyl)
  or a ketone group at position 3

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Steroids
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Important Steroids

• Cholesterol
• Bodys building block for other steroids
• Vitamins (D,K)
• Sex Hormones
• Testosterone
• Estrogen
• Bile Salts (aid in digestion)
• Carotenoids (pigments)
• Diagrams for many of these in structure packet

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Cholesterol

• Comes from animal cell membranes
• Necessary in the body in small amounts to build
  other steroids

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Sex Hormones
Estrogen
Testosterone