Fats and Lipids
Lipids
• Lipids are varied in structure.
– Many are insoluble in water because they lack
polar groups.
Types of Lipids and their Functions
– 1. Fat provides insulation and energy storage.
– 2. Phospholipids form plasma (cell)
membranes
– 3. Steroids are important cell messengers.
– 4. Waxes are for protection/insulation.
Lipids
• Fats and Oils =3 fatty acids + Glycerol
– A fatty acid is a long hydrocarbon chain with
a carboxyl (acid) group at one end. (-COOH)
• Because the carboxyl group is a polar
group, fatty acids can be slightly soluble in
water.
• Most fatty acids in cells contain 16 to 18
carbon atoms per molecule. The longer
the chain the less water soluble it is.
– Glycerol is a water-soluble compound with
three hydroxyl groups.
Lipids
• Triglycerides are glycerol joined to
three fatty acids by condensation
synthesis.
– Fats are triglycerides containing saturated
fatty acids (e.g., butter is solid at room
temperature). Generally from animals
– Oils are triglycerides with unsaturated fatty
acids (e.g., corn oil is liquid at room
temperature). Generally from plants
– **Animals use fat rather than glycogen for
long-term energy storage; fat stores more
energy.(9cal/g)
Types of Fatty Acids
• Saturated fatty acids have no double
bonds between their carbon atoms.
• Unsaturated fatty acids have double
bonds in the carbon chain where there are
less than two hydrogens per carbon atom.
• Saturated animal fats are associated with
circulatory disorders; plant oils can be
substituted for animal fats in the diet.
Lipids
• Waxes
– Waxes form a protective covering that prevent
water loss in plants, maintain animal skin and fur.
Steroids
– Cholesterol is a part of an animal cell’s
membrane and a precursor of other steroids,
including the sex hormones.
– Testosterone is the male sex hormone.
– Steroids act as messengers and help turn on
or turn off genes. Thus they help control cell
activity
Lipids
Phospholipids
– Phosphate group is the polar head
– Hydrocarbon chains become the
nonpolar tails.
Hey! Hey! Hey! This is why
phospholipids are important!!
– The plasma membrane which
surrounds living cells is a
phospholipid bilayer.