Exam 2 Study Guide - Carbohydrates Flashcards
Basic structure of a monosaccharide.
- aldehydes or ketones with at least two hydroxyl groups (CH2On)
- unbranched carbon chains with single bonds linking all carbon atoms…one carbon atoms is double-bonded to an oxygen atom to form a carbonyl group, all other carbon atoms are bonded to hydroxyl groups (OH).
Understand the difference between aldose and ketose sugars.
- aldose: carbonyl group is at an end of the carbon chain
- ketose: carbonyl group is at any other position
Epimers.
two sugars that differ by only one chiral carbon
Stereoisomers – Understand the difference between the α and β.
α Stereoisomer: OH on the carbonyl carbon is opposite CH2OH
β Stereoisomer: OH on the carbonyl carbon is on the same side as CH2OH
Disaccharides: Define, know the basic examples.
2 monosaccharides covalently bonded (Ex. Lactose, sucrose, trehalose)
O-glycosidic bond.
covalent linkage joining two monosaccharides (formed when a hydroxyl group of one sugar molecule reacts with the anomeric carbon of the other)…readily hydrolyzed by acid
Distinguish reducing vs nonreducing sugars.
- Reducing: have an anomeric carbon available for additional bonds
- Non-reducing: anomeric carbon is occupied (Ex. Sucrose and trehalose)
Homopolysaccharide vs heteropolysaccharide.
- Homopolysaccharide: single monomeric sugar species
- Heteropolysaccharides: two or more types of monomers
Starch: Where is it found?
Plant storage of glucose (stored in granules in the cell)
Starch: Composition and structure
Composed of 2 polymers [amylose…(a1-4 bond) and amylopectin (a1-4 bond unbranched regions; a1-6 bond branched regions)]…chains of D-glucose
Glycogen: Where is it found?
Animal storage of glucose (abundant in liver and skeletal muscle)
Glycogen: Composition and structure
- Similar to starch (a1-4 bond unbranched regions; a1-6 bond branched regions)…more compact than starch (branches every 8-12 monomers)
Both starch and glycogen form a (Blank).
coiled helix
Cellulose: Where is it found?
Cell wall of plants
Cellulose: Composition and structure
- Linear polysaccharide of D-glucose; beta conformation (B1-4 glycosidic bond)
- OH groups form hydrogen bonds with a chain or between neighboring chains
Why can’t many organisms digest cellulose?
Humans cannot digest cellulose because we don’t have digestive enzymes (no cellulase or bacteria in our gut) that are able to break apart (hydrolyze) the B1-4 glycosidic bonds that hold the monosaccharides in cellulose together. Since we are not able to break cellulose down, it can act as fiber which helps moves food through our digestive tract.
Chitin: Where is it found?
Exoskeleton of arthropods
Chitin: Composition and structure
Linear chain of N-acetylglucosamine (B1-4 linkage)…more hydrophobic than cellulose
Peptidoglycans: Where is it found?
Bacterial cell wall
Peptidoglycans: Structure
Heteropolymer of alternating (B1-4) linked N-acetylglucosamine and N-acetylmuramic acid residues…cross-linked by short peptides
Describe in general the composition of the extracellular matrix
Complex of carbohydrate and proteins outside of animal cells that connect cells together and provide a substrate for the cells to grow (network of heteropolysaccharides and fibrous proteins)
Dihydroxyacetone is a ketotriose. Explain what this means.
Dihydroxyacetone is a ketotriose because the carbonyl group is at any other position, besides the end of the carbon chain and it is composed of three carbons.
What molecule is released when 2 monosaccharides are bonded together to form a disaccharide?
H2O
