4.1 Carbohydrate Classification [HY]

Question 1

What is the most direct source of chemical energy for almost all organisms?

Answer 1

Carbohydrates

Question 2

Monosaccharides

Answer 2

• the most basic structural units of carbohydrates

Question 3

Trioses

Answer 3

• The simplest monosaccharides, contain three carbon atoms
• Carbohydrates with four, five, and six carbon atoms are called tetroses, pentoses, and hexoses

Question 4

Aldoses

Answer 4

Carbohydrates that contain an aldehyde group as their most oxidized functional group

Question 5

Ketoses

Answer 5

those with a ketone group as their most oxidized functional group

Question 6

Numbering carbon atoms in monosaccharide

Answer 6

• The carbonyl carbon is the most oxidized, and therefore
  will always have the lowest possible number
• In an aldose, the aldehyde
  carbon will always be carbon number one (C-1)
• The aldehyde carbon can participate in glycosidic linkages; sugars acting as substituents via this linkage are called glycosyl residues.
• the carbonyl carbon is C-2. Ketoses can also
  participate in glycosidic bonds at this carbon

Question 7

Names of important monosaccharides

Answer 7

• D-fructose, D-glucose, D-galatcose, D-mannose

Question 8

Enantiomers

Answer 8

• A special type of isomerism exists between stereoisomers that are nonidentical, nonsuperimposable mirror images of each other
• d-glucose and L-glucose

Question 9

Optical isomers (stereoisomers)

Answer 9

compounds that have the
same chemical formula; these molecules differ from one another only in terms of the spatial arrangement of their component atoms

Question 10

Chiral Carbon

Answer 10

• one that has four different groups attached to it
• any molecule that contains chiral carbons and no internal
  planes of symmetry has an enantiomer

Question 11

How can you determine the # of possible stereoisomers?

Answer 11

• can exist for a multi-carbon compound, identify the number of chiral carbons (n) and plug into the formula 2^n
• As the number of chiral carbons increases, so too does the number of possible stereoisomers because one
  compound may have many diastereomers.

Question 12

How are hydroxides oriented on the highest numbered chiral center for L & D?

Answer 12

all d-sugars have the hydroxide of their highest-numbered chiral center on the right, and all L-sugars have that hydroxide on the left.

Question 13

Diastereomers

Answer 13

Two sugars that are in the same family (both are either ketoses or aldoses, and have the same number of carbons) that are not identical and are not mirror images of each other

Question 14

Epimers

Answer 14

A special subtype of diastereomers are those that differ in configuration at exactly one chiral center.

Question 15

How many enantiomers and diastereomers does a compound have?

Answer 15

a compound can have only one enantiomer (the left hand to its right hand, or vice versa), but may have multiple diastereomers, depending on how many (and which) chiral carbons are inverted between the two molecules.