30 Questions
What is the basic composition of carbohydrates?
(CH2O)n
What is a monosaccharide?
A simple sugar with multiple OH groups
What is the chemical formula for glucose?
C6H12O6
Which sugar has the highest relative sweetness?
Fructose
What type of group do aldoses have at one end?
Aldehyde group
What is the simplest of the aldoses?
D-glyceraldehyde
Which term describes the varying sweetness of different monosaccharides?
Arrangement differences
What does it mean when a sugar solution is described as dextrorotatory?
It turns the plane of polarized light to the right
What type of bond is formed when the anomeric hydroxyl and another compound join together?
Glycosidic bond
Which sugar derivative has an amino group that substitutes for a hydroxyl group?
Glucosamine
What type of form does methyl-D-glucoside take when reacting with methanol?
$\alpha$-D-glucopyranose
What accounts for the differences in sweetness among glucose, fructose, and galactose?
Carbon chain length
What type of glycosidic bond holds together two glucose units in maltose?
α(1→4)
Which disaccharide is composed of galactose & glucose with a β(1→4) glycosidic linkage?
Lactose
What is the product of cellulose breakdown that is the equivalent β anomer of maltose?
Cellobiose
Which disaccharide has a glycosidic bond linking the anomeric hydroxyls of glucose & fructose?
Sucrose
What type of glycosidic bond holds together α-D-glucose &β-D-fructose units in sucrose?
(α1→2)
What is the full name of lactose?
β-D-galactopyranosyl-(1→4)α-D-glucopyranose
What is the relationship between two aldotetroses that are stereoisomers and mirror images of each other?
They are enantiomers
What type of reaction occurs when an aldehyde reacts with an alcohol?
Hemiacetal formation
What is the difference between a hemiacetal and a hemiketal?
A hemiacetal is formed from an aldehyde and a hemiketal is formed from a ketone
What are anomers?
Stereoisomers formed when a ring is formed
What is the rule for drawing the highest numbered carbon for D-sugars in Haworth projections?
It is drawn up
What is the relationship between two aldohexoses that differ only in the position of the hydroxyl group on one asymmetric carbon (carbon 4)?
They are epimers
Which sugar is the principal sugar in milk?
Lactose
Which of the following sugars is a non-reducing sugar?
Sucrose
What happens to the rotation of sucrose in solution when it is hydrolyzed?
It changes from dextrorotatory to levorotatory
Which polysaccharide is the most common storage polysaccharide in plants?
Starch
What is the primary polymeric form of glucose storage in plants?
Starch
Which type of amylose is a glucose polymer with α(1→4) linkages?
α-amylose
Study Notes
Carbohydrates (Glycans)
- General composition: (CH2O)n
- Classified into four categories: monosaccharides, disaccharides, oligosaccharides, and polysaccharides
Monosaccharides (Simple Sugars)
- Characteristics:
- Energy-containing molecules
- Provide structure
- Basic building block: (CH2O)n; n = 3, 5, 6
- Classified by number of carbons and type (aldose or ketose)
- Examples:
- Glucose (C6H12O6)
- Fructose
- Galactose
- D-glyceraldehyde (simplest aldose)
Disaccharides
- Definition: 2 monosaccharides covalently linked
- Examples:
- Maltose (α-D-glucose units linked by α(1→4) glycosidic bond)
- Sucrose (α-D-glucose and β-D-fructose units linked by α(1→2) glycosidic bond)
- Lactose (β-D-galactose and β-D-glucose units linked by β(1→4) glycosidic bond)
Glycosidic Bonds
- Formation: anomeric hydroxyl and a hydroxyl of another sugar or compound join together, splitting out water
- Example: methanol reacts with the anomeric OH on glucose to form methyl glucoside
Sugar Derivatives
- Amino sugars: an amino group substitutes for a hydroxyl (e.g., glucosamine)
- Acetylated amino sugars: amino group may be acetylated (e.g., N-acetylglucosamine)
Optical Activity
- Dextrorotatory (+): sugar solution turns the plane of polarized light to the right
- Levorotatory (-): sugar solution turns the plane of polarized light to the left
- Racemic mixture: equimolar mixture of optical isomers has no net rotation
Polysaccharides
- Definition: polymers consisting of chains of monosaccharide or disaccharide units
- Examples:
- Starch (plant storage polysaccharide, composed of amylose and amylopectin)
- Amylose (glucose polymer with α(1→4) linkages)
- Amylopectin (glucose polymer with varying lengths and molecular weights)
Miscellaneous
- Relative sweetness of different sugars:
- Sucrose: 100
- Glucose: 74
- Fructose: 174
- Lactose: 16
- Invert Sugar: 126
- Maltose: 32
- Galactose: 32
- Hemiacetal and hemiketal formation: reaction between an aldehyde or ketone and an alcohol to form a hemiacetal or hemiketal, respectively
Learn about the basic composition of carbohydrates (glycans) with the general formula (CH2O)n. Explore the classification of carbohydrates into monosaccharides, disaccharides, oligosaccharides, and polysaccharides based on the number of carbons in the molecules.
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