LECTURE 19
Wednesday 3/22/17
DISACCHARIDES
• Disaccharides are two monosaccharide units linked together
by acetal or ketal
• A
is identified by:
• the numbers associated with the carbon atoms joined
together by the linkage.
• the configuration of the linkage for any anomeric
carbon atom joined by the linkage.
IMPORTANT DISACCHARIDES
• Maltose is:
• malt sugar.
•
• formed during the digestion of starch to glucose.
• found in germinating grain.
• a hemiacetal,
• hydrolyzed to form two molecules of D-glucose.
IMPORTANT DISACCHARIDES (continued)
• Lactose is:
• milk sugar (5% cow milk, 7% human milk by weight).
• composed of galactose and glucose units joined by
• a hemiacetal, which means lactose is a
IMPORTANT DISACCHARIDES (continued)
• Sucrose is:
• common household
sugar.
• composed of fructose
and glucose units joined
by
• found in many plants
(especially sugar cane
and sugar beets).
•
• hydrolyzed to produce
invert sugar (a mixture
of equal amounts
glucose and fructose).
IMPORTANT DISACCHARIDES (continued)
IMPORTANT DISACCHARIDES (continued)
POLYSACCHARIDES
• Polysaccharides are condensation polymers containing
thousands of units.
• They are
• They can form thick colloidal dispersions when heated in
water.
• Starch is used as a thickener in sauces, gravies, pie fillings,
and other food preparations.
IMPORTANT POLYSACCHARIDES
• Starch is:
• a polymer consisting of
• a
form of D-glucose in plants.
• one of two forms, which are:
• unbranched amylose (10-20%), which is composed of
1000-2000 glucose units with
IMPORTANT POLYSACCHARIDES
(continued)
• and branched amylopectin (80-90%)
IMPORTANT POLYSACCHARIDES
(continued)
• Amylose
complexes with
iodine to form a
dark blue color.
The molecular conformation of
starch and the starch-iodine
complex: (a) the helical
conformation of the amylose chain
and (b) the starch-iodine complex.
IMPORTANT POLYSACCHARIDES
(continued)
• Glycogen (animal starch) is:
• a polymer
• used by animals to store
glucose, especially in the
liver and muscles.
•
IMPORTANT POLYSACCHARIDES
(continued)
• Cellulose is:
• a polymer of
• the most important structural
polysaccharide.
• the most abundant organic
compound on earth.
• found in
• a linear polymer like amylose, but
has
• not easily digested and a
constituent of dietary
IMPORTANT POLYSACCHARIDES
(continued)
• Cellulose structure:
CHAPTER 18
Lipids
IMPORTANT FUNCTIONS OF LIPIDS
•
•
•
•
coatings found on some plants
compounds with low densities
form of energy for plants and animals
components, especially in cellular membrane
formation
LIPID CLASSIFICATION (continued)
• Saponifiable lipids contain an ester that can undergo basic
hydrolysis.
•
contain one or more fatty acids and
an alcohol.
•
•
are ester-containing lipids with more
than two types of components: an alcohol, fatty acids, and
other components.
•
•
lipids do not contain an ester and cannot be
hydrolyzed.
•
LIPID CLASSIFICATION
• Lipids are biological compounds that are soluble only in
nonpolar solvents.
FATTY ACIDS
• Fatty acids:
• are the building blocks of many lipids.
•
• have long
responsible for fatty/oily
characteristics.
• The carboxyl group is very
under
conditions of physiological pH
FATTY ACIDS (continued)
• In water, fatty acids will form spherical clusters called
•
are important for biological functions, like the
transport of insoluble lipids in the blood.
FATTY ACIDS (continued)
• Fatty acids are:
• usually straight chains (no branching).
• usually from
• usually an
number of carbons.
• either saturated
or unsaturated
FATTY ACIDS (continued)
• Examples of saturated, monounsaturated, and
polyunsaturated fatty acids containing 18 carbon atoms
include:
FATTY ACIDS (continued)
• Cis carbon-carbon double bonds causes “kinking”of the carbon
chain.
FATTY ACIDS (continued)
• Fatty acids with C=C bonds
cannot pack closely together
because of shape. This leads to
• Fatty acid melting points
• Most unsaturated fatty acids are
at room temperature.
FATTY ACIDS (continued)
•
are those needed by the body,
but not synthesized within the body in adequate amounts.
• For humans, linoleic and linolenic acid are essential, but easily
obtainable from plant and fish oils.
FATTY ACIDS (continued)
• Linoleic (an omega-3 fatty acid) and linolenic (an omega-6
fatty acid) acids:
• are used to produce hormonelike substances that regulate
a wide range of functions and characteristics, including:
• e.g. blood pressure, blood clotting, blood lipid levels,
the immune response, and the inflammation response
to injury and infection.
• can be converted to other omega-3 and omega-6 fatty
acids.