BIOCHEMISTRY LECTURE / FIRST SEMESTER
CARBOHYDRATES
LEARNING OBJECTIVES
FUNCTIONS OF CARBOHYDRATES
I. Define carbohydrates
II. Describe the difference between monosaccharides, 1. Energy Sources:
oligosaccharides, and polysaccharides and explain Monosaccharides- glucose, galactose and fructose
the system used to categorize monosaccharides Polysaccharides- starch and glycogen
III. Identify four important disaccharides and describe 2. Supporting Structures:
how the monosaccharide residues in them are joined Bacterial and plant cell walls (cellulose—linear glucose
to another polymer)
IV. Distinguish homopolysaccharides from Cartilage (modified monosaccharides, ex. glucosamine)
heteropolysaccharides
Exoskeletons in arthropods (insects, crabs and lobsters)
3. Components of nucleic acids DNA and RNA--ribose and
CARBOHYDRATES AND BIOCHEMISTRY deoxyribose
4. Immune system--Oligosaccharides (3-30 sugars) modify cell
Carbohydrates are compounds of tremendous surface proteins to identify native versus foreign cells
biological importance: 5. Signal transduction systems--Many cell surface receptor
- They provide energy through oxidation proteins have carbohydrate side groups that are critical for
- They supply carbon for the synthesis of cell function
components
- They serve as a form of stored chemical energy CLASSES OF CARBOHYDRATES
- They form part of the structures of some cells and
tissues Monosaccharides contain a single polyhydroxy
aldehyde or ketone unit
Carbohydrates, along with lipids, proteins, nucleic
Oligosaccharides contain 2 to 10 monosaccharide
acids, and other compounds are known as
units
biomolecules because they are closely Polysaccharides contain very long chains of
associated with living organisms hundreds or thousands of monosaccharide units,
which may be either in straight or branched chains
CARBOHYDRATES
Most substances of this class have empirical formulas THE STEREOCHEMISTRY OF
suggesting that they are carbon hydrates CARBOHYDRATES
–a carbohydrate is any molecule that contains the elements
C, H, and O in a 1:2:1 ratio
–the sizes of carbohydrates vary TWO FORMS OF GLYCERALDEHYDE
→ simple carbohydrates – made up of one or two
monomers
→ complex carbohydrates – long polymers Glyceraldehyde, the simplest
These substances have important biological roles carbohydrate, exists in two isomeric forms
Building block is simple sugar or monosaccharide
Carbohydrates or saccharides(saccharon is Greek for “sugar”)
that are mirror images of each other:
are polyhydroxy aldehydes or ketones, or substances that yield
such compounds on hydrolysis
Carbohydrates include not only
sugar, but also the starches
that we find in food, such as
bread, pasta and rice.
The term carbohydrate comes
from the observation that when
you heat sugars, you get SOPHIA NICOLE POSERIO MACAM
carbon and water. UNIVERSIDAD DE MANILA
BSN- 14
, BIOCHEMISTRY LECTURE / FIRST SEMESTER
CARBOHYDRATES
STEREOISOMERS 2^n Rule
These forms are When a molecule has more than one chiral carbon,
stereoisomers of each each carbon can possibly be arranged in either the
other.
right-hand or left-hand form, thus if there are n chiral
Glyceraldehyde is a chiral
carbons, there are 2^n possible stereoisomers.
molecule – it cannot be
superimposed on its mirror FISCHER PROJECTIONS
image. The two mirror-
image forms of
Fischer projections are a
glyceraldehyde are convenient way to represent
enantiomers of each other. mirror images in two
dimensions
CHILARITY AND HANDEDNESS Place the carbonyl group at
or near the top and the last
Chiral molecules have the achiral CH2OH at the bottom
same relationship to each
other that your left and NAMING STEREOISOMERS
right hands have when
When there is more than one chiral center in a
reflected in a mirror carbohydrate, look at the chiral carbon farthest from
the carbonyl group:
– If the hydroxy group points to right when the
carbonyl is up, it is the D-isomer
– If the hydroxy group points to the left, it is the L-
CHIRAL CARBONS isomer
Chiral objects cannot be superimposed on their
mirror images
Achiral objects can be superimposed on the
mirror images
Chiral carbon - Any carbon atom which is
connected to four different groups will be chiral,
and will have two nonsuperimposable mirror
What’s so great about chiral molecules?
images
Many organic compounds, including Molecules which are
carbohydrates, contain more than one chiral enantiomers of each other have
exactly the same physical
carbon
properties but not their
interaction with polarized light
CHIRAL CARBON ATOMS Polarized light vibrates only in
one plane; it results from
passing light through a
polarizing filter
OPTICAL ACTIVITY
• A levorotatory (–) substance rotates polarized light to the left
[e.g., l-glucose; (-)-glucose].
• A dextrorotatory (+) substance rotates polarized light to the
right [e.g., d-glucose; (+)-glucose].
• Molecules which rotate the plane of polarized light are
optically active.
• Many biologically important molecules are chiral and optically
active. Often, living systems contain only one of the possible
stereochemical forms of a compound, or they are found in
separate systems. SOPHIA NICOLE POSERIO MACAM
UNIVERSIDAD DE MANILA
BSN- 14
CARBOHYDRATES
LEARNING OBJECTIVES
FUNCTIONS OF CARBOHYDRATES
I. Define carbohydrates
II. Describe the difference between monosaccharides, 1. Energy Sources:
oligosaccharides, and polysaccharides and explain Monosaccharides- glucose, galactose and fructose
the system used to categorize monosaccharides Polysaccharides- starch and glycogen
III. Identify four important disaccharides and describe 2. Supporting Structures:
how the monosaccharide residues in them are joined Bacterial and plant cell walls (cellulose—linear glucose
to another polymer)
IV. Distinguish homopolysaccharides from Cartilage (modified monosaccharides, ex. glucosamine)
heteropolysaccharides
Exoskeletons in arthropods (insects, crabs and lobsters)
3. Components of nucleic acids DNA and RNA--ribose and
CARBOHYDRATES AND BIOCHEMISTRY deoxyribose
4. Immune system--Oligosaccharides (3-30 sugars) modify cell
Carbohydrates are compounds of tremendous surface proteins to identify native versus foreign cells
biological importance: 5. Signal transduction systems--Many cell surface receptor
- They provide energy through oxidation proteins have carbohydrate side groups that are critical for
- They supply carbon for the synthesis of cell function
components
- They serve as a form of stored chemical energy CLASSES OF CARBOHYDRATES
- They form part of the structures of some cells and
tissues Monosaccharides contain a single polyhydroxy
aldehyde or ketone unit
Carbohydrates, along with lipids, proteins, nucleic
Oligosaccharides contain 2 to 10 monosaccharide
acids, and other compounds are known as
units
biomolecules because they are closely Polysaccharides contain very long chains of
associated with living organisms hundreds or thousands of monosaccharide units,
which may be either in straight or branched chains
CARBOHYDRATES
Most substances of this class have empirical formulas THE STEREOCHEMISTRY OF
suggesting that they are carbon hydrates CARBOHYDRATES
–a carbohydrate is any molecule that contains the elements
C, H, and O in a 1:2:1 ratio
–the sizes of carbohydrates vary TWO FORMS OF GLYCERALDEHYDE
→ simple carbohydrates – made up of one or two
monomers
→ complex carbohydrates – long polymers Glyceraldehyde, the simplest
These substances have important biological roles carbohydrate, exists in two isomeric forms
Building block is simple sugar or monosaccharide
Carbohydrates or saccharides(saccharon is Greek for “sugar”)
that are mirror images of each other:
are polyhydroxy aldehydes or ketones, or substances that yield
such compounds on hydrolysis
Carbohydrates include not only
sugar, but also the starches
that we find in food, such as
bread, pasta and rice.
The term carbohydrate comes
from the observation that when
you heat sugars, you get SOPHIA NICOLE POSERIO MACAM
carbon and water. UNIVERSIDAD DE MANILA
BSN- 14
, BIOCHEMISTRY LECTURE / FIRST SEMESTER
CARBOHYDRATES
STEREOISOMERS 2^n Rule
These forms are When a molecule has more than one chiral carbon,
stereoisomers of each each carbon can possibly be arranged in either the
other.
right-hand or left-hand form, thus if there are n chiral
Glyceraldehyde is a chiral
carbons, there are 2^n possible stereoisomers.
molecule – it cannot be
superimposed on its mirror FISCHER PROJECTIONS
image. The two mirror-
image forms of
Fischer projections are a
glyceraldehyde are convenient way to represent
enantiomers of each other. mirror images in two
dimensions
CHILARITY AND HANDEDNESS Place the carbonyl group at
or near the top and the last
Chiral molecules have the achiral CH2OH at the bottom
same relationship to each
other that your left and NAMING STEREOISOMERS
right hands have when
When there is more than one chiral center in a
reflected in a mirror carbohydrate, look at the chiral carbon farthest from
the carbonyl group:
– If the hydroxy group points to right when the
carbonyl is up, it is the D-isomer
– If the hydroxy group points to the left, it is the L-
CHIRAL CARBONS isomer
Chiral objects cannot be superimposed on their
mirror images
Achiral objects can be superimposed on the
mirror images
Chiral carbon - Any carbon atom which is
connected to four different groups will be chiral,
and will have two nonsuperimposable mirror
What’s so great about chiral molecules?
images
Many organic compounds, including Molecules which are
carbohydrates, contain more than one chiral enantiomers of each other have
exactly the same physical
carbon
properties but not their
interaction with polarized light
CHIRAL CARBON ATOMS Polarized light vibrates only in
one plane; it results from
passing light through a
polarizing filter
OPTICAL ACTIVITY
• A levorotatory (–) substance rotates polarized light to the left
[e.g., l-glucose; (-)-glucose].
• A dextrorotatory (+) substance rotates polarized light to the
right [e.g., d-glucose; (+)-glucose].
• Molecules which rotate the plane of polarized light are
optically active.
• Many biologically important molecules are chiral and optically
active. Often, living systems contain only one of the possible
stereochemical forms of a compound, or they are found in
separate systems. SOPHIA NICOLE POSERIO MACAM
UNIVERSIDAD DE MANILA
BSN- 14
