Organic Macromolecules: Lipids
I.
Introduction to Macromolecules
A. Many of the organic molecules within the
human body are classified as
macromolecules.
1. The term “macromolecule” literally
means “giant molecule”
(“macro-” = giant)
2. Macromolecules are often referred to as
polymers which means that they are
formed by joining together many (100’s1000’s) of repeating units called
monomers.
II. Structures of Lipids
A. Most macromolecules join together to
form long chains but lipids can join
together to form large, globular
molecules.
1. The composition and conformation of
lipids depends on the type of lipid you
are referring to
Triglycerides are composed of one glycerol
molecule and three fatty acid chains
Phospholipids have one glycerol molecule, two
fatty acid chains, and a charged/polar
phosphate group
Steroid Lipids can form long chains or twist in on
themselves to form rings
III. Functions of Lipids
A. Lipids tend to either store energy, make
the primary structure of plasma
membranes, be a primary component of
hormones, provide pigment, or stabilize
plasma membranes.
B. Lipids that primarily store excess energy
are triglycerides
Triglycerides – a simple lipid in which
three fatty acids are combined with one
molecule of glycerol
An illustration of a triglyceride molecule would
be:
Glycerol
1. Triglycerides are the different types of fats
found in our foods.
1. Triglycerides can either be solids or liquids at
room temperature (20OC)
a. Triglycerides (fats) that are solid at room
temperature have saturated fatty acid
chains attached to glycerol.
Saturated Fatty Acid Chain – a fatty acid
molecule consisting only of carbon and
hydrogen atoms with NO double bonds
between any of the carbon atoms
*This configuration maximizes the number of
hydrogen atoms bound to carbon atoms*
b. Oils are liquid at room temperature and are
considered to be unsaturated fatty acids.
Unsaturated Fatty Acid chain – a fatty acid
molecule consisting only of carbon and
hydrogen atoms with one or more double
bonds between any of the carbon atoms.
Saturated Fatty Acid Chain
Unsaturated Fatty Acid Chain
C. Lipids that make up the basis of biological
membrane are phospholipids.
Phospholipids – cellular materials that have a
phosphorus containing component that can
dissolve in organic solvents
1. Because of the two unique parts of the
phospholipid they form a two-layer
membrane in cells and cellular organelles.
Hydrophilic Polar Head – “water loving”
portion of a phospholipid that is polar and
dissolves in water
Hydrophobic Nonpolar Tail – “water
fearing” portion of a phospholipid that is
nonpolar and does not dissolve in water
An illustration of phospholipids and how they form
membranes would be:
Hydrophilic
Hydrophobic
D. Lipids that are a part of hormones or
pigments form long chains or rings or carbon
and hydrogen atoms.
1. Pigments in plants and animals come from
carotenoids.
Carotenoids – a yellow, orange, or red lipid
pigment commonly found as an accessory
pigment in photosynthesis
a. In humans carotenoids, specifically carotene, can be broken down into two
vitamin-A molecules which are the
building blocks for rhodopsin, a protein
that helps our eyes interpret light.
2. Lipids made up of carbon atoms that
are bonded in the shape of a ring are
called steroids.
Steroids – any of numerous lipids
based on a 17-carbon atom ring
system
a. Many steroids make up hormones.
Cortisone plays a role in regulating the
digestion of carbohydrates and proteins,
salt and water balance, and sexual
development. It also plays a role in
handling stress.
Testosterone/Estrogen regulates sexual
development in male/female vertebrates
E. Another common steroid that helps to
stabilize plasma membranes is
cholesterol.
Cholesterol is the starting material for
making testosterone, several other
steroid hormones, and for the bile salts
that aid in the digestion of fats. It is also
found holding plasma membranes
together .
What is too much cholesterol?:
HDL: High Density Lipoprotein is considered
“good cholesterol” picks up extra cholesterol
and delivers it to the liver to be
metabolized. [Want to raise this number]
LDL: Low Density Lipoprotein is considered
“bad cholesterol” transports cholesterol in
the blood and may lead to atherosclerosis
(hardening/narrowing of the arteries) [Want
to lower this number]
HDL/LDL Ratio being researched as an
indicator for health disease.
*Currently it is believed it should be >0.3
(ideally it would be >0.4)