Flashcards in Lecture 14 - Carbohydrates Deck (48):
What kind of bond are monosaccharides (simple sugars) joined by to make oligosaccharides?
Polymer with up to thousands of monosaccharides units
List the monosaccharide properties
Colorless crystalline solid
freely soluble in water, but insoluble in nonpolar solvents
unbranched carbon chains
common mono- and disaccharide names end in "-ose"
True or false? Simple sugars do not have chiral centers and are therefore optically inactive.
FALSE. Simple sugars have chiral centers and therefore optically active.
What are two sugars differing in configuration at only one carbon are called?
What are sugars characterized by?
By chiral center most distant from the carbonyl carbon
Name the six carbon sugars that are common in nature
How is hemiacetal formed?
An OH group reacts with the C=O from an aldehyde
How is hemiketal formed?
An OH group reacts with the C=O from an ketone
What forms O-glycosidic linkage?
2nd OH addition to C=O
When is anomer labeled as the α-anomer?
OH is on opposite side of C6 (down)
When is anomer labeled as the β-anomer?
OH on the same side as C6 (up)
True or false? Equatorial substituents have more steric hindrance than axial
How can conversion between anomers happen?
Spontaneously in water via mutarotation
What trap sugars within the cell and activate them for further chemistry?
Phosphorylated derivatives (of sugars)
___________ contain a single type of monosaccharides.
Give examples of Homopolysaccharides
___________ containing two or more varieties of monosaccharides
What are homopolysaccharides used for?
Energy storage and as structural elements (cellulose, chitin)
Function of heteropolysaccharides
Provide extracellular support for organisms (peptidoglycans)
Sugars are very water soluble due to what?
Large number of OH groups
Function of starch
An important energy storage role in plants
A polymer of (α1 --> 4)-linked D-glucose
Function of glycogen
Provides long-term energy storage role in animals and fungi
What's the branching on glycogen?
α1 --> 6 branching every 8 to 12 residues
Bacterial and yeast polysaccharides of (α1 --> 6)-linked poly-D-glucose
Possible branches of dextrans
α1 --> 3
α1 --> 2
α1 --> 4
What breaks down glycogen, starch, and dextrans?
Enzymes in saliva
What's the structure of cellulose like?
Unbranched polymer of D-glucose units are connected by β-1 --> 4 glycosidic bonds (neighbors flipped 180°)
True or false? Fungi produces cellulase
Homopolymer containing N-acetyl-D-glucosamine with β1-->4 bonds
Describe the structure of bacterial cell wall
Contains bacterial peptidoglycan, a heteropolymer of alternating (β1-->4)-linked N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) with peptide crosslinks
What's the purpose of bacterial peptidoglycan?
Prevents cellular swelling and lysis in water
Proteins glycosylated with covalently attached glycosaminoglycans
Proteins glycosylated (N-link or O-link) with oligosaccharides of varying complexity
Glycosylated lipids in outer face of plasma membrane, and in nervous tissue
True or false? Glycosylation patterns are not important recognition and signaling
False, THEY ARE
Core proteins with glycosaminoglycans covalently attached at serine residues
What's the general sequence for proteoglycans?
True or false? Cell – ECM interactions anchor cells and provide paths for cell migration during development
True or false? Cell – ECM interactions convey information across the plasma membrane unidirectionally
How is glycoprotein different than proteoglycan?
Glycoprotein glycans are smaller, more branched, and more structurally diverse than proteoglycans.
The linking of glycans through glycosidic bonds to -OH of Ser or Thr
The linking of glycans through glycosidic bonds to amide N of Asn
True or false? Glycosylation encodes information to signal where protein should go, cell – cell interactions, differentiation and tissue development
True or false? Glycosylation is much more diverse than protein and DNA/RNA sequences
Proteins that bind carbohydrate groups with high affinity and selectivity by reading the sugar coat