LIPIDS

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LIPIDS

• Lipids are hydrophobic molecules composed of C,
  O, and H. In general, they contain fewer O-H
  bonds and more C-H bonds than carbohydrates do.
  If they are hydrophobic, what will they dissolve
  in?
•  

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WHAT DO ORGANISMS USE LIPIDS FOR?

• Storing Energy
• Building Membranes and other cell parts
• Chemical Signaling Molecules

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Types of Lipids (families)

• Fats
• Phospholipids
• Steroids
• Waxes

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Fats

• Most common energy storing molecule
• 1 gram of fat stores 38 kJ (9 kilocalories)
• (one calorie (cal) 4.18 J, 1 Cal (1kcal) 4.18
  kJ
• What is a calorie?

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Adipose Tissue

• Animals convert excess carbohydrate to fat
• Fat molecules are stored in fat droplets in the
  cells of adipose tissue
• The layer of fat beneath the skin acts as thermal
  insulation

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Adipose tissue
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Plants and fats

• Plants store fats as oils
• Fats and oils are made from two kinds of
  molecules glycerol and fatty acids

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Structure of Fatty Acids

• tail of a fatty acid is a long hydrocarbon
  chain (16 -18 carbons long), making it
  hydrophobic. The head of the molecule is a
  carboxyl group which is hydrophilic.

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Most common lipid

• Triglycerides
• Glycerol and 3 fatty acids

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Saturated vs Unsaturated Fatty Acids

• Saturated fatty acids have only single bonds
  between carbons atoms
• They are saturated because they have the maximum
  number of H bonds attached to the carbons
• Unsaturated fatty acids have one or more carbon
  carbon double bonds
• They have fewer than the maximum number of H
  bonds attached to the carbons

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Poly and mono saturated

• Polyunstaturated fatty acids
• Have many CC bonds
• Monounsaturated fatty acids have one CC bond

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Solid vs liquid

• Straight chains of fatty acids allows them to fit
  together very closely allowing van der Waals
  forces along the length
• (Van der Waals forces occur between molecules of
  the same substance
• They include dipole forces, dispersion forces and
  hydrogen bonding)
• Result is solid consistency at room temperature

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Solid vs Liquid

• Unsaturated fatty acids are commonly found in
  plant oils
• The bending of the hydrocarbon chains with CC
  prevents/reduces van der Waal attractions,
  causing oils to be liquid at room temperature
• (see page 36 in text)

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Hydrogenation

• Industrial process that adds H atoms to the CC
  bonds of unsaturated fatty acids rendering
  vegetable oils to be solid at room temperature

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Cis and Trans Fatty Acids
Trans
Cis

• The Latin prefixes Cis and Trans describe the
  orientation of the hydrogen atoms with respect to
  the double bond.
• Cis means "on the same side" and
• Trans means "across" or "on the other side".
• Naturally-occurring unsaturated vegetable oils
  have almost all cis bonds
• Trans fatty acids are carcinogenic

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Phospholipids

• glycerol two fatty acids a phosphate group

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Hydrophobic and Hydrophilic

• The fatty acids - hydrophobic,
• The phosphate group - hydrophilic
• This means that phospholipids are soluble in both
  water and oil.

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Micelle

• When added to water, phospholipids form spheres
  micelles. (see page 38)
• The hydrophilic heads dissolve in water, the
  hydrophobic tails mix in the centre of the sphere

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Membranes and Phospholipids

• Cell membranes - double layer of phospholipids
• Fatty acids form inside
• Phosphate group face out on both surfaces.

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Function of Cell Membrane

• Separates two water compartments
• Cytoplasm and extracellular fluid
• Allows two areas to distinct
• Homework describe a cell membrane and the
  function of it.
• http//www.cytochemistry.net/Cell-biology/membrane
  _intro.htm

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Steroids
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Good Steroids

• Estrogen, progesterone, corticosteroids,
  aldosterone, testosterone, and Vitamin D.
• Four fused hydrocarbon rings and functional
  groups.

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Cholesterol

• Precursor to sex hormones and Vitamin D
• Sunlight changes cholesterol to Vit. D
• Is important part of cell membranes
• Gives a fluid nature to membrane in colder
  temperatures

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Artherosclerosis

• Read Page 38 of your text and describe what this
  is.

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Waxes

• Long chain fatty acids linked to alcohols or
  carbon rings
• They form firm, pliable molecules
• Useful as waterproof coatings for plants and
  animals
• Cutin covers leaves, stems and fruit
• Beeswax used to construct honeycombs

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Task

• Questions 11 18 on page 40