BIOCHEM WEEK 3 Flashcards
• most abundant class of bioorganic molecules on planet Earth
Carbohydrates
CHO in plants
– structural elements
Cellulose
CHO in plants
energy reserve
Starch
provides energy.
Oxidation
Storage
glycogen
– for synthesis of other biologic substances
C atom source
DNA and RNA structural component
ribose & deoxyribose
Cell membrane component
glycolipids
Cell-cell and Cell-Molecule recognition processes
glycoprotein
largest source of dietary calories for most of the world’s population
Carbohydrates
• A carbohydrate that contains a single polyhydroxy aldehyde or polyhydroxy ketone unit or
• Cannot be broken down into simpler units by hydrolysis
• Usually contains 3-7 carbon atoms
• Water-soluble
• Crystalline solids
MONOsaccharide
• 2 monosaccharides covalently bonded to each other
• Produces monosaccharides upon hydrolysis
• Water-soluble
• Crystalline
DIsaccharide
• 3-10 monosaccharides covalently bonded to each other
• Produces monosaccharides upon hydrolysis
• Mostly not digested by human enzymes
Examples
• Raffinose • Stachyose
OLIGOsaccharide
• MANY monosaccharides covalently bonded to each other
• Produces monosaccharides upon hydrolysis
Examples
• Glycogen • Cellulose • Starch
POLYsaccharide
• name ends in –ose
§ except: Glyceraldehyde &
Dihydroxyacetone
• can be classified based on
§ number of carbons v Triose
v Tetrose v Pentose v Hexose
§ functional group v Aldose
v Ketose
Monosaccharides
have the same molecular and structural formulas but differ in orientation of atoms in space
The left and right-handed forms of a chiral molecule
isomers
nonsuperimposable mirror images
e.g. left- and right-handed forms of a molecule
Enantiomers
not mirror images of each others
Diastereomers
Type of isomerism founds in carbohydrates
§ Superimposable
§ Non-superimposable
– C atom bonded to 4 different groups
Chiral Center
(t or f)
• All proteins, most fats, and all common carbohydrates are chiral
true
are almost always right-handed
Monosaccharides
are always left-handed
Amino acids
2D notation for showing the spatial arrangement of groups about chiral centers in molecules
• Chiral center is represented as the intersection of vertical and horizontal lines
Fischer Projection
(t or f)
§ D stands for Dextro – right
§ L stands for Levo - left
true
Isomers in which the atoms have different connectivity
Constitutional Isomers
isomers with atoms of the same connectivity that differ only in the orientation of the atoms in space
Stereoisomers
Stereoisomers
Stereoisomers that are non superimposable mirror images of each other.
Handedness (D and L forms) is determined by the configuration at the highest- numbered chiral center
Enantiomers
Stereoisomers
Stereoisomers that are nit mirror images of each other.
diastereomers
(t or f)
Enantiomers are OPTICALLY ACTIVE – it rotates the plane of polarized light
• If it rotates the plane polarized light towards the RIGHT (clockwise) → + DEXTROROTATORY
• If it rotates the plane polarized light towards the LEFT (counter clockwise) → - LEVOROTATORY
true
(t or f)
Handedness (D & L) of enantiomers & the direction of
light rotation are NOT connected entities
true
The two members of an enantiomeric pair have the SAME interaction with __________________
ACHIRAL molecules
The two members of an enantiomeric pair have DIFFERENT interactions with __________________
CHIRAL molecules
• Name due to its resemblance to the cyclic ether Pyran
• Cyclic monosacchoride containing a 6-atom ring
PYRANOSE
• Name due to its resemblance to the cyclic ether Furan
• Cyclic monosacchoride containing a 5-atom ring
FURANOSE
• 2D structural notation that specifies the 3D structure of the cyclic form of a monosaccharide
• hemiacetal ring system viewed “edge on” with the –O– ring atom at the
§ upper right (6 membered ring) or
§ top (5-membered ring)
Haworth Projection
can yield 3 different types depending on the oxidizing agent
Oxidation
Yields polyhydroxy alcohols referred to as ___________
ALDITOLS
(t or f)
Hydroxyl groups (–OH) can react with inorganic oxyacids to form inorganic esters
true
Amino sugars and their N-acetyl derivatives are building blocks of glycosaminoglycans such as ___________
hyaluronic acid
(t or f)
• Hydroxyl group (–OH) of a monosaccharide is replaced with an amino group (NH2)
• In naturally occurring amino sugars, NH2 replaces the C2 –OH group
true
Fact: the cyclic form of monosaccharides are ___________
hemiacetals
–OH group is replaced with an –OR group
Hemiacetal carbon
(grape sugar)
• Most abundant in nature
• Nutritionally the
most important
• Used by cells as the
primary source of energy
GLUCOSE
(brain sugar)
• Seldom encountered as a
free monosaccharide
• Synthesized in the
mammary glands for use in
lactose (milk sugar)
• Component of glycoproteins
found in nervous tissue
• Also present in the chemical markers
that distinguish various blood types
GALACTOSE
glucose
optically active
Dextrose
glucose
blood contains
dissolved glucose
§ Insulin - ↓ glucose level
§ Glucagon - ↑ glucose level
Blood sugar
(fruit sugar)
• Most important ketohexose
• Sweetest-tasting of all sugars
• Sometimes as a dietary
sugar because it requires a smaller amount to reach the same amount of sweetness
FRUCTOSE
Fructose
optically active
Levulos
• Pentose
• Important component of RNA and energy-rich compounds
RIBOSE
• Important component of DNA molecules
• lacks an Oxygen atom at the 2nd carbon compared to ribose
DEOXYRIBOSE
• Malt sugar
• Produced by the breakdown of the polysaccharide starch
• Common ingredient in baby foods and malted milk
• 1 glucose + 1 glucose linked by an ⍺(1→4) linkage
• Can be broken down by the enzyme maltase
Maltose
• Milk sugar
• Synthesized by mammalian mammary glands by in a 4 step process • Common ingredient in commercially-produced infant formula
• 1 glucose + 1 lactose linked by a β(1→4) linkage
• Can be broken down by the enzyme lactase
Lactose
• Table sugar
• Most abundant disaccharide
• Commercially produced from sugar cane and sugar beets
• 1 glucose + 1 fructose linked by a β(1→2) linkage
• Can be broken down by the enzyme sucrase
• NONREDUCING
Sucrose
• Also referred to as Glycans
• Polymer that contains many monosaccharide units bonded to each other by glycosidic linkages
• Not sweet, not positive for Tollen’s or Benedict’s Test
• Limited water solubility - –OH groups can individually become hydrated, resulting in thick colloidal suspensions of polysaccharides
§ Used as thickening agents in sauces, desserts, and gravy
Polysaccharide
The identity of repeating monosaccharide units
only 1 type of monosaccharide
Homopolysaccharides
The identity of repeating monosaccharide units
two or more types of monosaccharide
Heteropolysaccharide
• Energy storage homopolysaccharide found in PLANTS
• Composed solely of glucose units
• Amylose – unbranched (15-20%) bonds: ⍺(1→4)
MM: 50,000 (up to 1k glucose units) Amylopectin – branched (80-85%) bonds: ⍺(1→4) ⍺(1→6) at branch points every 25-30 units MM: 300,000 (up to 100k glucose units)
• Hydrolyzed by enzymes of the human digestive tract
STARCH
• Energy storage homopolysaccharide found in ANIMALS & HUMANS
• Composed solely of glucose units
• Stored in the liver and muscle
• Bonds: ⍺(1→4)
⍺(1→6) at branch points
• MM: 3,000,000 (up to 1M glucose units)
GLYCOGEN
• Structural homopolysaccharide found in PLANT CELL WALL
• Monomer: glucose
• Bonds: β(1→4)
• Most abundant polysaccharide
• NOT hydrolyzed by enzymes in the human digestive tract
• Serves as dietary fiber – readily absorbs water leading to softer stools
CELLULOSE
• Structural homopolysaccharide found in ARTHROPODS & FUNGI
• Monomer: N-acetyl-D-glucosamine Bonds: β (1→4)
• 2nd most abundant polysaccharide
• NOT hydrolyzed by enzymes in the human digestive tract
CHITIN
• Alternating residues of N-acetylglucosamine and D-glucuronic acid
• Bonds: β(1→3) alternating with β(1→4)
• 50,000 disaccharide units/chain
• Found as lubricant fluid of joints and in the vitreous humor of the eye
HYALURONIC ACID
• Alternating residues of Sulfated iduronic acid and Sulfated glucosamine
• Blood anticoagulant naturally present in mast cells & is released at the site of tissue injury
• Used therapeutically to inhibit coagulation of blood
HEPARIN
• lipid molecule that has ≥ 1 carbohydrate (or derivative) units covalently bonded to it
Functions
• Cerebrosides & Gangliosides –
found extensively in neural tissue • Essential cell membrane
component
Glycolipids
• protein molecule that has ≥ 1 carbohydrate (or derivative) units covalently bonded to it
Functions
• Immunoglobulins
• Cell surface recognition and
antigenicity
• Lubricant and protective agent in
the gastrointestinal and urogenital tracts
Glycoproteins
mono or disaccharides (sugars) - sweet
Simple carbs
polysaccharides – not sweet
Complex carbs
naturally present in whole foods such as milk and fruit; accompanied by nutrients
Natural suga
separated from its plant source (usually beet, cane); considered as empty calories
Refined sugar
