Carbohydrates Flashcards
what is the general formula for a carbohydrate
(CH2O)n
what is the difference between an aldehyde and a ketone
- the carbonyl of an aldehyde is at the end of a carbon chain whereas the carbonyl of a ketone is between two carbon atoms
define epimer
- two isoforms that differ only in the configuration around one chiral carbon
What happens to monosaccharides in aqueous solution
- monosaccharides with 5 or more carbon atoms occur predominantly as cyclic structures in aqueous solution
- creates a chiral center
what is an anomeric carbon?
- the chiral carbon created in the cyclization of monomers in aqueous solution
- occurs at the carbonyl carbon of an ester
What is mutarotaion
- interconversion between the alpha and beta rings in aqueous solution
- rings break and reseal
- will eventually reach equilibrium state and Beta will be more abundant
Define reducing end
the end of a disaccharide or a polysaccharide with a free anomeric carbon (not involved in a glycosidic bond)
define a reducing sugar
- one of the anomeric carbons is not involved in a glycosidic bond
define nonreducing disaccharides/sugars
both anomeric carbons are involved in a glycosidic bond
- What information can you determine from the following disaccharide naming abbreviations: Glc(α1–>4)Glc. Glc(α1<–>α1)Glc
Glc(α1–>4)Glc
- the reducing sugar is on the left and in the alpha configuration
- sugar on the right is nonreducing and carbon 4 is involved in the glycosidic bond
- it is a reducing sugar
Glc(α1<–>α1)Glc
- both sugars are in the alpha configuration and the glycosidic bond is between the two anomeric carbons
- it it a nonreducing sugar
definition and example of homopolysaccharide
- a carbohydrate made up of repeating units of a single type of sugar monomer, also known as a monosaccharide
- ex: fuel storage (starch, glycogen), structural elements (cellulose, chitin)
definition and example of heteropolysaccharides
- carbohydrate made up of two or more types of monomers
- ex: Extracellular support (peptidoglycan, ECM)
how are starch and glycogen stored in the cell? why?
- they are stored as granules because then they are insoluble and reduce the concentration of glycogen in cells
- if stores as monomers, too much water would enter through osmosis
- cells need to be able to take up glucose from the cell. if stored as monomers, there is too high of a concentration up reasonable take up into the cell
from which end (reducing or nonreducing) are residues cleaved to mobilize energy from glycogen or starch? why?
- enzymes cleave glucose/starch from the nonreducing ends
- enzymes can work simultaneously on many branches
- fast conversion of the polymer to glucose units
How are the 3D conformations of glycogen and cellulose different? What type of interactions stabilize these structures?
- glycogen is typically a tightly coiled helix (60° dihedral angle)
- stabilized by hydrogen bonds
- cellulose typically stored linearly
- 180° diheral angles
- stabilized by both inter and intra-chain H-bonds
what is a lectin?
- proteins that bind carbohydrates with high specificity and moderate to high affinity
- this binding can influence cell signaling, adhesion, and intracellular targeting
