sp14 9carbohydrates
TRANSCRIPT
-
8/13/2019 Sp14 9Carbohydrates
1/20
MO figure
Carbohydrates
-
8/13/2019 Sp14 9Carbohydrates
2/20
Topics Covered in this Module
Diversity of Structure and Function in Carbohydrate Molecules
Polysaccharides
Major Objectives of this Module
Classify monosaccharides based on molecular characteristics.
Relate structures of polysaccharides to their functions in cells and
organisms.
Understand how monosaccharides are classified based on molecular
characteristics.Explain how a glycosidic linkage forms by a dehydration synthesis
reaction.
Classify monosaccharides based on molecular characteristics.
Relate structures of polysaccharides to their functions in cells andorganisms.
Understand how monosaccharides are classified based on molecular
characteristics.
Explain how a glycosidic linkage forms by a dehydration synthesis
reaction.
-
8/13/2019 Sp14 9Carbohydrates
3/20
Polymer - A high molecular weight compound consisting oflong chains that may be open, closed, linear, branched, orcross-linked.
The chains are composed of repeating units, called
monomers, which may be identical or different.
Macromolecules are Polymers
-
8/13/2019 Sp14 9Carbohydrates
4/20
HO
HO
Polymerization is a dehydration reaction: monomer in,
water out
HO
H
OH+ Water
H
Monomer
Monomer
H
H
OHH
Monomer
MonomerHO+
H
HO
HO
H
H
Water
Depolymerization is a hydrolysis reaction: water in, monomer out
-
8/13/2019 Sp14 9Carbohydrates
5/20
Carbohydrates are commonly classified on the basis oftheir size.
Monosaccharides
Disaccharides (2) Oligosaccharides (3-10)
Polysaccharides (many)
Carbohydrate = carbon hydrate or hydrated carbon atoms.
One carbonyl (C=O), many hydroxyls.
Classification of Carbohydrates
-
8/13/2019 Sp14 9Carbohydrates
6/20
LE 5-3Triose sugars
(C3H6O3)
Glyceraldehyde
Pentosesugars
(C5H10O5)
Ribose
Hexose sugars (8 types)
(C6H12O6)
Glucose Galactose
Dihydroxyacetone
RibuloseFructose
Aldehyde: carbonyl carbon (C=O) is terminal
Ketone: carbonyl carbon (C=O) is internal
Ps
-
8/13/2019 Sp14 9Carbohydrates
7/20
Figure 1c
General empirical formula for carbohydrates = (CH2O)n.
-
8/13/2019 Sp14 9Carbohydrates
8/20
Figure 1d
-
8/13/2019 Sp14 9Carbohydrates
9/20
-
8/13/2019 Sp14 9Carbohydrates
10/20
Figure 5
Disaccharides form by
dehydration synthesis. The
covalent bond is called aglycosidic linkage, the #s
refer to the carbons
involved.
-
8/13/2019 Sp14 9Carbohydrates
11/20
Polysaccharides, the polymers of sugars, can be either
structural molecules (cellulose) or energy storage
molecules (amylose, amylopectin, glycogen)
The structure and function of a polysaccharide are
determined by its sugar monomers and the positionsof glycosidic linkages
Polysaccharides
-
8/13/2019 Sp14 9Carbohydrates
12/20
Amylose - The form of starch that is composed of long, (thousands)
unbranched chains of glucose units which are joined by means of
(1-4) glycosidic bonds.
Amylopectin - The form of starch that is composed of long, branched
chains of glucose units which are joined by means of (1-4) and (1-
6) glycosidic bonds. Branching =~ 1 in every 30 monomers.
Glycogen - A highly branched homopolysaccharide of D-glucose units
that is the major form of storage of carbohydrate in animals (ie in
liver and muscle); the glucose units are linked by means of (1-4) and
(1-6) glycosidic bonds. Branching =~ 1 in every 10 monomers
Energy Storage Polysaccharides
-
8/13/2019 Sp14 9Carbohydrates
13/20
Figure 10b
-
8/13/2019 Sp14 9Carbohydrates
14/20
Figure 10c
-
8/13/2019 Sp14 9Carbohydrates
15/20
Figure 7
Glycogen granules in mouse liver, starch granules in plant
chloroplast. Glycogen and starch are energy storagepolysaccharides composed of glucose
-
8/13/2019 Sp14 9Carbohydrates
16/20
Structural Polysaccharides: Cellulose
Branch-free linear structure.
Linear chain of several hundreds or thousands of beta
glucose monomers.
Allow hydrogen bonding to occur between adjacentcellulose molecules.
Result in strong, parallel groupings of molecules called
microfibrils. May be the most abundant organic compound on Earth.
Primary component of tough walls that enclose plant cells.
-
8/13/2019 Sp14 9Carbohydrates
17/20
Figure 10a
-
8/13/2019 Sp14 9Carbohydrates
18/20
Enzymes that digest starch by hydrolyzing alpha linkages cant
hydrolyze beta linkages in cellulose
Cellulose in human food passes through the digestive tract as
insoluble fiber
Some microbes use enzymes to digest cellulose
Many herbivores, from cows to termites, have symbiotic
relationships with these microbes
-
8/13/2019 Sp14 9Carbohydrates
19/20
Summary
OBJECTIVE Classify monosaccharides based on molecular characteristics.
Carbohydrates are organic compounds that include a carbonyl group and several
hydroxyl groups. Based on their number of constituent monomers, carbohydrates
are classified into monosaccharides, disaccharides, oligosaccharides, andpolysaccharides. Monosaccharides are further classified based on three main
characteristics, including
the location of their carbonyl group
the length of their carbon skeleton, which is most often between three and seven
carbon atoms
the spatial arrangement of hydroxyl groups around asymmetric carbons
OBJECTIVE Explain how a glycosidic linkage forms by a dehydration synthesis
reaction.
Glycosidic linkages form through dehydration synthesis reactions, which have a
water molecule as a by-product. In this type of reaction, two monosaccharides
form a covalent bond by giving up a water molecule and result in a disaccharide.
This process can continue when many monosaccharides polymerize to form
polysaccharides. The covalent bond formed between two monosaccharides is
called a glycosidic linkage. The type of constituent monomers and the glycosidic
bonds that make up the structure dictate the structure and function of
polysaccharides.
-
8/13/2019 Sp14 9Carbohydrates
20/20
OBJECTIVE Relate structures of polysaccharides to their functions in cells and
organisms.
Organisms use a diversity of polysaccharides for energy storage, structural
support, cellular identity purposes, and synthesis of other molecules. The most
common polysaccharides include starch, glycogen, cellulose, chitin, andpeptidoglycan. Carbohydrates have important functions in cells. These functions
are related to the structures of the associated molecules. Starch and glycogen
serve as energy-storage molecules in plants and animals, respectively. These
molecules are composed of glucose monomers joined by 14 glycosidic linkages.
The alpha () form of the glucose monomers makes these polysaccharides
relatively accessible for energy supply. Cellulose, chitin, and peptidoglycan providestructural support to various organisms. These macromolecules include
monosaccharides joined by 14 glycosidic linkages, which makes them more
difficult to degrade. Oligosaccharides, unique combinations of about 210
monosaccharides, are located on cell-surface glycoproteins. They function to
communicate a cells type or species.