Chapter 13 Lipids
Tiara Bartol and Brant Houghton
13.1 What are lipids?
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Family of substances that are
insoluble in water but soluble in
nonpolar solvents and solvents of
low polarity
Defined in terms of properties
Classification of Function
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3 roles

Storage energy within fat cells

Part of membranes that separate
compartments of aqueous solutions

Serve as chemical messengers
Storage

Important in animals

Use fats for storage
Glycogen
Greater amount of energy
 9 Kcal/g

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Membrane Component
 Lipids lack water solubility
 The body needs insoluble
compounds for membranes that
separate aqueous solutions
 Derives from smaller polar groups
than alkane like portions
 Nonpolar provide hydrophobic part

Messengers
 Primary messenger delivers
signals from one part of body to
another
 Steroid hormones
 Secondary messenger meditates
hormonal response
 prostaglandins and
thromboxanes
Classification by Structure

4 groups
 Simple lipids
 Fats and waxes
 Complex lipids
 Steroids
 Prostaglandins, thromboxanes,
and leukotrienes
13.2 What are structures of
Triglycerides?

Triglyceride
 Animal fats and plant oils
 Triesters of glycerol and long
chain carboxylic acids called fatty
acids
Even number of acids
 Aka triacylglycerols
 3 groups of glycerol are esterified
 Complex mixtures
 Most cases 2 or 3 different fatty
acids are present
 Hydrophobic character is caused
by long chain
 Esters are buried in nonpolar
environment which makes them
insoluble


Fatty acids
 Practically all unbranched
carboxylic acids
 10 to 20 carbosn
 Even # of carbons
Cis isomer predominates
Mono and diglycerides
 Not infrequent
 Latter two sides
 1 or 2 OH groups are esterified
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13.3 What are properties of
Triglycerides?
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Fats
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A mixture of triglycerides
containing a high proportion of
long chain, saturated fatty acids
Oils

A mixture of triglycerides
containing a high proportion of
long chain, unsaturated fatty acids
or short chain, saturated fatty
acids

Physical State
Fats are generally solids at room
temperature
 Fats from plants and fish are
liquids
 Liquid fats are oils
 Solid fats are mainly saturated
fatty acids
 Vegetable oil has high amounts of
unsaturated fatty acids
 Essential fatty acids


The body needs but can’t synthesize

Most oils contain large amounts of
unsaturated fatty acids

Coconut oil has a small amount
Polyunsaturated fatty acids have
more than one double bond
 Pure fats and oils are colorless,
odorless, and tasteless
 To gain taste substances must be
added

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Hydrogenation
Easy to convert unsaturated
liquids and oils to solids
 Don’t hydrogenate all double
bonds
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It will become too solid
This is the source of trans fatty
acids
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Saponification
Base promoted hydrolysis of fats
and oils
 Produce glycerol and a mixture of
fatty acids called soap
 It is the oldest known chemical
reaction
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