FT LEC: Carbohydrates Flashcards
are polyhydroxylated aldehydes or ketones; or compounds that yield polyhydroxylated aldehydes or ketones upon hydrolysis
Carbohydrates
are the most abundant class of bioorganic molecules on Earth
Carbohydrates
Produced by green plants (chlorophyll-containing) via photosynthesis
Carbohydrates
Function of carbohydrates in plants
- Serve as structural elements in the form of cellulose
- Provide short term storage in the form of starch
Classification of Carbohydrates
- Monosaccaharide
- Disaccharide
- Oligosaccharide
- Polysaccharide
are classified according to the type of carbonyl group present and the number of carbon atoms in the open chain
Monosaccharides
A monosaccharide is characterized by the number of C atoms in its chain
3 carbons = triose
4 carbons = tetrose
5 carbons = pentose
6 carbons = hexose
are the simplest carbohydrates; usually contain three to six carbon atoms in an open chain with either an aldehyde or a ketone in one end with multiple hydroxyl group
Monosaccharides
Appear as white, crystalline solids
Monosaccharides
water-soluble and taste sweet
Carbohydrates
The simplest monosaccharides; serve as important intermediates in glycolysis
Glyceraldehyde and Dihydroxyacetone
a chiral molecule
Glyceraldehyde (D-Glyceraldehyde)
achiral molecule
Dihydroxyacetone
The most abundant monosaccharide in nature, and most important from a nutritional standpoint
D-Glucose
Found in large amounts in ripe fruits particularly grapes(grape sugar)
D-Glucose
Two other names of D-glucose
- Dextrose
- Blood sugar
draws attention that D-glucose is optically active and rotates plane polarized light to the right (dextrorotatory)
Dextrose
because the blood contains dissolved glucose (70mg/dL) regulated by the hormones insulin and glucagon
Blood sugar
Seldom found as a free monosaccharide
D-Galactose
Epimer of D-glucose at carbon 4
D-Galactose
Synthesized from D-glucose in the mammary glands and bonds with D-glucose to form lactose
D-Galactose
Found on the membranes of different cell types
D-Galactose
Biochemically the most important ketose
D-Fructose
the sweetest-tasting of all sugars; found in fruits (also known as fruit sugar), and honey in equal amounts with glucose
D-Fructose
Also known as levulose because a solution of naturally occurring ________ rotate plane polarized light to the left
D-Fructose
Used as a dietary sugar; less is needed for the same amount of sweetness
D-Fructose
A aldopentose
D-Ribose
Component of nucleic acids, and energy-rich ATP
D-Ribose
Exists as 2-deoxy-D-ribose in DNA
D-Ribose
are composed of two monosaccharides linked together by acetals also known as glycosidic linkages
Disaccharides
is the bond between two monosaccharide units resulting from the reaction between the hemiacetal carbon atom –OH group and an –OH group on the other monosaccharide
glycosidic linkages
Made up of two D-glucose units connected by α(1>4) glycosidic linkage
Maltose
Also known as malt sugar
Maltose
An intermediate in the hydrolysis of cellulose
Cellobiose
Composed of two D-glucose units connected by β(1>4) glycosidic linkage
Cellobiose
Cannot be digested by humans
Cellobiose
Composed of β-D-galactose unit bonded to D-glucose by β(1>4) glycosidic linkage
Lactose
drolyzed by the enzyme lactase
Lactose
The most abundant disaccharide in nature; found in plants
Sucrose
Carbohydrates that contain 3 to 10 monosaccharide units
Oligosaccharides
Composed of α-D-glucose and β-D-fructose linked by α(1>2)β
Sucrose
Rarely found a free molecules; usually components of more complex molecules
Oligosaccharides
play an important role in distinguishing blood types
Oligosaccharides
act as biochemical markers on the plasma membrane of red blood cells
Oligosaccharide molecules
The following monosaccharides contribute to the makeup of the oligosaccharide “marking system”:
α-D-Galactose
α-L-Fucose
α-N-Acetyl-D-glucosamine
α-N0Acetyl-D-galactosamine
no fifth unit
Type O
N-Acetyl-galactosamine as 5th unit
Type A
Galactose as 5th unit
Type B
contain hundreds to thousands of monosaccharide units
Polysaccharides
Also known as glycans
Polysaccharides
are repeating units in a polymer chain
Monomers
only one type of monosaccharide monomer is present
Homopolysaccharides
more than one (usually two) type of monosaccharide monomer is present
Heteropolysaccharides
Common storage polysaccharides
- Starch in plants
- Glycogen in animals
Serve as structural elements in plant cell walls and animal exoskeletons
- Cellulose in plants
- Chitin in animal exoskeletons
Polysaccharides with disaccharide repeating units in which one of the component is an amino sugar or both have negative charges due to the presence of sulfate group or carboxylic acid group
Acidic Polysaccharides
Found in connective tissues in humans
Acidic Polysaccharides
found in joints and in the vitreous humor of the eye
Hyaluronic acid
highly sulfated polysaccharide; acts as a naturally occurring anticoagulant in the blood present in mast cells in sites of tissue injury
Heparin
Lipid molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it
Glycolipid
Protein molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it
Glycoprotein
