LIPIDS

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LIPIDS

• By D. Jones

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Characteristics of Lipids

• little or no affinity for water
• NOT polymers
• mostly hydrocarbons (small amount of O)

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Fats

• assembled through dehydration synthesis
• glycerol
• three carbon alcohol
• three hydroxyl groups
• three fatty acids
• long carbon skeleton (16-18 C)
• carboxyl group on one end
• may be the same or different
• C-H bonds make them nonpolar (hydrophobic)

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• Ester linkages
• hydroxyl group bonds to carboxyl group
• Triglyceride

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Types of Fats

• saturated
• no double bonds in fatty acid chains
• solid at room temperature
• from animals
• Lard butter
• lead to atherosclerosis
• unsaturated
• one or more double bonds
• causeskink
• Keep molecules from packing closely together
• liquid at room temperature
• fish and plant fats
• also called oils

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• hydrogenated oils
• unsaturated fats prepared by adding hydrogen
• Margarine, peanut butter, Crisco

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Health recommendations

• Limit saturated fats and transfatty acids
• animal fats, coconut oil palm oil
• hydrogenation produces transfatty acids
• Avoid commercial baked goods and fast foods.
• These cause cardiovascular disease.

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• Eat some polyunsaturated fats and monounsaturated
  fats
• Polyunsaturated safflower, sunflower, cotton
  seed oil fish
• Monounsaturated olive oil, canola oil, peanut
  oil

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Fat Substitutes Taken from Web MD

• Fat substitutes added to commercial foods or used
  in baking, deliver some of the desirable
  qualities of fat, but do not add as many
  calories. Some replacers, such as the cellulose
  gel Avicel, Carrageenan (made from seaweed), guar
  gum, and gum arabic, have been used for decades
  in many commercial foods and are generally
  recognized as safe. New, synthetic fat
  substitutes are now available, but little is
  known about their long-term effects. Olestra
  (Olean) passes through the body without leaving
  behind any calories from fat. (It should be
  noted, however, that foods containing olestra
  still have calories from carbohydrates and
  proteins.) Early reports of cramps and diarrhea
  after eating food containing olestra have not
  proven to be significant. Of greater concern is
  the fact that even small amounts of olestra
  deplete the body of certain vitamins and
  nutrients that are important for protection
  against serious diseases, including cancer. The
  FDA requires that the missing vitamins be added
  back to olestra products, but not other
  nutrients.
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Functions of fat

• energy storage
• 1 g fat has 2 X calories of 1 g carbohydrate
• stored in adipose cells
• swell and shrink as fat us used or stored
• cushion organs
• insulate

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Phospholipids

• glycerol backbone
• 2 fatty acid chains
• hydrophobic
• phosphate group
• negative charge
• hydrophilic
• in water assemble into micelle

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Cell Membranes

• phospholipids in a bilayer
• phosphate head associates with water outside
  water inside cell
• fatty acid tails point toward each otheraway
  from water
• forms boundary between cell and environment

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Sterols (Steroids)

• carbon skeleton organized into 4 fused rings
• differ by functional groups attached
• cholesterol
• precursor of other steroids
• many are hormones
• component of animal cell membranes

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Waxes

• fats combined with alcohol
• differ from fats in that glycerol is replaced by
  a sterol or by higher even-numbered aliphatic
  (straight chain) alcohols from C16 to C36
• protect from water loss in plants