BIOCHEM Chp.4 Carbs Flashcards
What is the simplest aldose?
glyceraldehyde (aldotriose)
What is the diff b/w ketose and aldose?
aldose - carbohydrates that contain an oxidized aldehyde at C1
ketose - carbohydrates that contain an oxidized ketone at C2
What is the simplest ketose?
dihydroxyacetone (ketotriose)
What is an optical isomer/stereoisomer?
compounds with the same chemical formula but different spatial arrangement of atoms
What is an enantiomer?
stereoisomers that are of the same sugar but are non-superimposable mirror images (have no plane of symmetry)
What is diastereomer?
two of the same sugar with eh me number of carbons but are not mirror images
What is the diff a b/w anomer and an epimer?
epimer: Diastereomers that differ eat only 1 chiral center
anomer: epimer that differs at the anomeric carbon
Which are the EU and NU in monosaccharides?
nucleophile = hydroxyl group
electrophile - carbonyl group
Why do 5 and 6 membrane rings assume a cyclic structure?
the furanose (5) and pyranose (6) rings adopt a chair-like configuration, and substituents assume axial or equatorial positions to minimize steric hindrance
What are the reagents used to detect the presence of reducing sugars?
Tollen [Ag(NH3)2] and Benedict (Cu2O)
What is a reducing sugar?
any monosaccharide with a hemiacetal ring
What is tautomerization?
the rearrangement of bonds in a compound, usually by moving H and forming a double bond
What is phosphorylation?
the catalyzation of glucose or glucokinase (in the liver and pancreatic B-islet cells) in which a phosphate ester is formed
What is a glycosidic bond?
C-O is formed when a hemiacetal/ketal reacts with an alcohol to form a acetal/ketal
What is the diff b/w furnanoside and pyranosides?
furnaosides = glycosides derived from furanose
pyranosodies = glycosides derived from pyranose
How are Di and polysaccharides formed?
from glycosidic bonds/linkages b/w monosaccharides via dehydration
How is cellobiose?
2 glucose joined by B-1,4 linkages
How is maltose formed?
2 glucose joined by a-1,4 linkages
How is cellulose formed?
homopolysaccharide chain of B-D-glucose linked by B-1,4 glycosidic bonds
How is amylose formed?
polysaccharide chain of a-D-glucose linked by a-1,4 glycosidic bonds
How is glycogen formed?
polysaccharide chain of a-D-glucose linked by a-1,6 glycosidic bonds
How is amylopectin formed?
polysaccharide chain of a-D-glucose linked by a-1,6 glycosidic bonds
What reagents test for the presence of starches?
Iodine - it fits inside the helix confirmation of amylose, forming an iodine-starch complex
What is the advantage of the branching of glycogen?
the branching optimizes energy efficiency making it more soluble in solution, thereby allowing more storage in the body, and the branching allows enzymes like glycogen phosphorylase to work on many sites within the molecule simultaneously
What is the diff b/w a and b-amylase?
the debranching enzyme, b-amylase cleaves amylose at the nonreducing end (end with acetal) of the polymer to yield maltose, while a-amylase cleaves randomly along the chain to yield shorter polysaccharides chain of maltose and glucose
How does glycogen phosphorylase work?
it cleves glucose from the nonreducing end of a glycogen branch and phosphorylation it, thereby producing glucose 1-phosphate
What is the diff b/w alpha and beta anomer?
alpha - OH of the anomeric carbon is trans to the free CH2OH group
beta - OH of the anomeric carbon is cis to the free CH2OH group
How is sucrose formed?
glucose-a-1,2-fructose
How is lactose formed?
galactose-b-1,4-glucose
What is esterification?
the reaction by which an OH group reacts with either a carboxylic acid or its derivatives to form an ester
