Chapter 10: Carbohydrates Flashcards
Define: Cellulose
The most abundant organic molecule in the biosphere
Define: Lectins
Carbohydrate-binding proteins
Define: Glycosyltransferases
Enzymes that synthesize oligosaccharides
Define: Epimers
Monosaccharides that differ at a single asymmetric carbon atom.
Define: Starch
The storage form of glucose in plants.
Define: Carbohydrates
Has the molecular formula of (CH2O)n.
Define: Proteoglycan
Glycoprotein containing glycosaminoglycans
Define: Mucoprotein
N-Acetylgalactosamine is a key component of this glycoprotein
Define: Glycogen
The storage form of glucose in animals.
Indicate whether each of the following pairs of sugars consists of anomers, Epimers, or an Aldose-Ketose pair:
D-glyceraldehyde and dihydroxyacetone
Aldose-ketose
Indicate whether each of the following pairs of sugars consists of anomers, Epimers, or an Aldose-Ketose pair:
D-glucose and D-mannose
Epimers
Indicate whether each of the following pairs of sugars consists of anomers, Epimers, or an Aldose-Ketose pair:
D-glucose and D-fructose
Aldiss-Ketose
Indicate whether each of the following pairs of sugars consists of anomers, Epimers, or an Aldose-Ketose pair:
a-D-glucose and B-D-Glucose
Anomers
Indicate whether each of the following pairs of sugars consists of anomers, Epimers, or an Aldose-Ketose pair:
D-ribose and D-ribulose
Aldose-Ketose
Indicate whether each of the following pairs of sugars consists of anomers, Epimers, or an Aldose-Ketose pair:
D-galactose and D-Glucose
Epimers
Glucose and fructose are reducing sugars. Sucrose, or table sugar, is a disaccharide consisting of both fructose and glucose. Is sucrose a reducing sugar? Explain.
No, sucrose is not a reducing sugar. The anomeric carbon atoms of glucose and fructose can act as the reducing agent, but, in sucrose, the two anomeric carbon atoms are joined by a covalent bond and thus not available to react.
Raffinose, a minor constituent in sugar beets, is a trisaccharide.
Is raffinose a reducing sugar? Explain.
Not a reducing sugar, no open-chain forms possible.
Raffinose, a minor constituent in sugar beets, is a trisaccharide.
What are the monosaccharides that compose raffinose?
D-Galactose, D-Glucose, and D-Fructose
Raffinose, a minor constituent in sugar beets, is a trisaccharide.
B-Glucosidase is an enzyme that will remove galactose residues from an oligosaccharide. What are the products of B-galactosidase treatment of raffinose?
D-Galactose and Sucrose (Glucose + Fructose)
A-D-Mannose is a sweet-tasting sugar. B-D-Mannose, on this other hand, tastes bitter. A pure solution of a-D-Mannose loses its sweet taste with time as it is converted into the B-anomer. Draw the B-anomer and explain how it is formed from the a-anomer.
The hemiketal linkage of the a-anomer is broken to form the open form. Rotation about the C-1 and C-2 binds allows the formation of the B-anomer, and a mixture of isomers results.
Fructose is in its B-D-pyranose form accounts for the powerful sweetness of honey. The B-D-Furanose form, although sweet, is not as sweet as the pyranose form. The furanose form is the more stable form. Explain why it may not always be wise to cook with honey.
Hearing converts the very sweet pyranose form into the more stable but less sweet furanose form. Consequently, the sweetness of the preparation is difficult to accurately control, which also accounts for why honey loses sweetness with time.
Why is the role of glycosaminoglycan in the cushioning provided by cartilage?
The glycosaminoglycan, because it is heavily charged, binds many water molecules. When cartilage is stressed, such as when your heel hits the ground, the water is released, thus cushioning the impact. When you lift your heel, the water rebinds.
Define: Enantiomers
Stereoisomers that are mirror images of each other
Carbohydrates are:
Aldehydes and ketones with two or more hydroxyl groups.
Fructose can cyclize to (a):
both pyranose and furanose ring forms.
The nutritional storage form(s) of glucose in plants:
Amylose and Amylopectin
To which amino acid residues in glycoproteins are the sugars commonly linked?
Serine, threonine, and asparagine.
All of the following are thought to play a role in cancer prevention EXCEPT:
Plants of the order Brassicales hydrolyze glucosinolates and that store organic isothiocyanates as a defense against herbivory.
When two carbohydrates are epimers:
They differ only in the configuration around one carbon atom.
When forming the disaccharide maltose from two glucose monosaccharides:
Water is eliminated and a hemiacetal is converted to an acetal.
Starch and glycogen are both polymers of:
alpha-D-glucose
