09 Lipids-06d

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Transcript 09 Lipids-06d

The Structure and
Function of
Macromolecules
Chapter 5
4 -- Lipids
Macromolecules:
The Molecules of Life
 Carbohydrates
 Nucleic Acids
 Proteins
 Lipids
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Lipids are a diverse group of
hydrophobic molecules
 Lipids – not polymers
 Hydrophobic
 Mostly hydrocarbons – non-polar covalent
bonds
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Fats/ Lipids
 Fats -- glycerol + fatty acids
 Glycerol -- three-carbon alcohol with –OH attached
to each carbon
 A fatty acid – -COOH attached to long carbon
skeleton
 Held together with ester linkage
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Lipids
 Oils and Fats – Oils are fats that are liquid at
room temperature
 Waxes – fatty acids and long chain alcohols
 Steroids -- 4 fused carbon rings
 Phospholipids -- phosphate group substituted
for one of the fatty acids
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LE 5-11a
Fatty acid
(palmitic acid)
Glycerol
Dehydration reaction in the synthesis of a fat
In a fat, three fatty acids are joined to glycerol by
an ester linkage, creating a triacylglycerol, or
triglyceride
LE 5-11b
Ester linkage
Fat molecule (triacylglycerol)
Fatty Acids
 Major function -- energy storage
 Fatty acids
 vary in length (number of carbons)
 Vary in number and locations of double bonds
 Saturated fatty acids -- maximum number of
hydrogens (no double bonds)
 Unsaturated fatty acids -- one or more double
bonds
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Fatty Acids
 Saturated fatty acids – saturated fats
 Most animal fats are saturated
 Saturated fats are solid at room temperature
 Linked to cardiovascular disease through plaque deposits
Stearic acid
Saturated fat and fatty acid.
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Fatty Acids
 Unsaturated fatty acids -- unsaturated fats
 Plant fats and fish fats are usually unsaturated
 Liquid at room temperature
Oleic acid
Unsaturated fat and fatty acid.
cis double bond
causes bending
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Waxes
 Waxes – long chain alcohols
 Fatty acid chains
 strongly hydrophobic
 Highly saturated -- solid at room temperature
 Waterproof coatings
 Leaves and stems of plants
 Fur in mammals
 Insect exoskeletons
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Waxes
Commercial uses of waxes
 Jojoba (southwestern desert plant) oil
similar to sperm whale oil and is used in
cosmetics
Candellila (Euphorbia antisyphilitica) wax
was used as a non-melting way to coat M &
Ms. Now seriously endangered.
Carnauba wax is from the carnauba palm
Bayberry wax for candles and scents
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Steroids
 Steroids -- carbon skeleton consisting of four fused
rings (not necessarily the same kind of ring!)
 Cholesterol -- component in animal cell membranes
 Many hormones
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Phospholipids
 Phospholipid -- 2 fatty acids and a phosphate group
 Fatty acid tails -- hydrophobic
 Phosphate group attachments -- hydrophilic head
 Amphipathic
 Phospholipid bilayer
 Membranes
 4 different kinds
 Choline
 Serine
 Ethanolamine
 Sphingolipids
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Membranes
 Phospholipids
 most abundant
 amphipathic
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Phosphate
group
Glycerol
Choline
Fatty acids
Water
Hydrophilic
head
Hydrophobic
tail
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Fig. 3-13, p. 58
LE 5-14
Hydrophilic
head
Hydrophobic
tails
WATER
WATER
Membranes
 Membrane – phospholipid bilayer
 Embedded proteins determine function
 Different phospholipids on inside/outside
Outside of cell
Carbohydrate side chain
Hydrophilic
region
Inside of cell 0.1 µm
Hydrophobic
region
Hydrophilic
region
TEM of a plasma membrane
Phospholipid
Proteins
Structure of the plasma membrane
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Membranes
wikipedia
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Lanolin
 Not a wax, per se, but related to waxes
 Mixture of cholesterol and esters of fatty acids
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Olean ™
 Fat – glycerol plus 3 fatty acids
 Olestra (Olean) – sucrose plus eight fatty acids
 Olean is too large to move through the intestinal
wall
 since it does not contain glycerol, the fatty acids can
not be removed from the sucrose molecule for
digestion
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