Monosaccharides and their Properties Flashcards
Define monosaccharides
the simplest form of carbs that can’t be further hydrolyzed into sugars
Monosaccharides are colorless, ______ solids that are _______ in water, but insoluble in _______ solvents. Most have a _____ taste.
crystalline
very soluble
nonpolar
sweet
What is the backbone of common monosaccharides?
unbranched carbon chains
-all the carbons are linked by single bonds
What is the backbone of common monosaccharides?
unbranched carbon chains in which all the carbons are linked by single bonds
The carbon atoms are given numbers starting from _________. In glucose, the first carbon is the __________ group.
the first carbon
aldehydic group
Nomenclature ; According to the presence of an aldehyde or ketone group:
-Ose means:
aldose (containing an aldehyde group)
ketose (containing a ketone group)
-ose means sugar
Nomenclature: According tot he number of carbon atoms:
trioses (monosacchrides containing 3 carbons) tetroses (4) pentoses (5) hexoses (6) heptoses (7)
Nomenclature: According to the presence of an aldehyde or ketone groups and number of carbon atoms
- aldotriose and keto triose
- aldotetrose and ketotetrose
- aldopentoses and ketopentose
Trioses
- aldotriose (glyceraldhyde)
- ketotrioses (dihydroxyaceton)
- review the structure
Tetroses
Monosaccharides containing 4 carbon atoms:
aldotetrose (erythrose)
ketotetrose (erythrulose)
Pentoses
5 carbon atoms
aldopentoses (ribose, arabinose, xylose, and lyxose)
ketopentoses (cellulose)
Function of pentoses
ATP GTP NAD NADP glycoproteins in animals and plants
Hexoses
Aldohexoses: glucose, mannose
ketohexose: fructose
What are the simplest monosaccharides?
the 2 three-carbon trioses:
D-glyceraldehyde (aldotriose)
dihydroxyacetone (ketotriose)
What are the most common monosaccharides in nature?
the aldohexose D-glucose
the ketohexose D-fructose
What are the components of nucleotides and nucleic acids?
the aldopentoses: D-ribose and 2-deoxy-D-ribose
Glucose is:
- the most important sugar of CHO
- the main sugar in blood
- one of the major sources of energy
Glucose Properties
- the straight-chain structural formula can account for some of the properties of glucose
- however, a cyclic structure is thermodynamically favored and accounts for other properties
What is a cyclic structure formed by?
the reaction between the aldehyde group and a hydroxyl group
Many of the carbon atoms to which hydroxyl groups are attached are __________. This gives rise to the man _________ found in monosaccharides.
chiral centers
stereoisomers
Stereoisomers
isomers that differ in spatial arrangement of atoms
Isomerism
Sugars exhibit various forms of _____.
isomerism
Isomers
molecules that have the same chemical formula but different chemical structures
Asymmetric Carbon
an important determinant of isomerism
Asymmetric carbon (2)
a carbon atom to which 4 different atoms or groups of atom are attached is said to be asymmetric
Presence of asymmetric carbon also ________.
exhibits optical activity on the compound
What happens when a beam of plane-polarised light is passed through a solution?
it will be rotated to the right or left in accordance with the type of compound
The Optical Isomers:
When it is rotated to the right, the compound is called ______.
When it is rotated to the left, the compound is called ________.
Dextrorotatory (D or + sign)
Laevorotatory (L or - sign)
What does the D-series and L-series refer to?
the orientation of the H and OH groups around the carbon atom just adjacent to the terminal primary alcohol carbon
Which atom in glucose determines the series?
C-atom 5
When the OH group on this carbon is on the right, it belongs to _______, when the - OH group is on the left, it is a member of _________.
D-series
L-series
2 isomers of glucose- D-glucose and L-glucose are
mirror images of each other
D- and L- isomers are
mirror images of each other (enantiomers)
Examples of D-Aldoses with 3 carbons are
Glyceraldehyde
Examples of D-Aldoses with 4 carbons are
D-erythrose
D-Threose
Examples of D-Aldoses with 5 carbons are:
D-ribose
D-arabinose
D-xylose
D-lyxose
Examples of D-Aldoses with 6 carbons are
D-allose D-altrose D-glucose D-mannose D-gulose D-idose D-galactose D-talose
Examples of D-Ketoses with 3 carbons
Dihydroxyacetone
Examples of D-Ketoses with 4 carbons
D-erythrulose
Examples of D-Ketoses with 5 carbons
D-ribulose
D-xylulose
Examples of D-Ketoses with 6 carbons
D-Psicose
D-Fructose
D-sorbose
D-tagatose
Epimerism
2 sugars which differ from 1 another only in configuraion around a single carbon atom are called epimers
Glucose and galactose are examples of
epimeric pairs which differ only with respect of C4
Mannose and glucose are epimers in respect of
C2
Epimerisation
process by which one epimer is converted to the other
it requires the enzyme epimerase
What is an example of epimerisation?
conversion of galactose to glucose in the liver
What is an example of epimerisation?
conversion of galactose to glucose in the liver
The cyclic forms of carbohydrates can exist in 2 forms
a- and b-
What are these 2 forms based on?
based on the position of the substituent at the anomeric center
The 2 forms are sometimes described as _____ since they are _______ at the anomeric center
anomers, isomers
When does a cyclic structure ‘take place’?
as the 2 reacting groups aldehyde and alcoholic group belong to the same molecule
Mutarotation
during dissolving of a saccharide in water the equilibrium between anomers is established
The rings structures of monosaccharides are similar to the ring structures of either
pryan or furan
Define pyran and furan
a 6-membered ring
a 5-membered ring
For glucose in solution, more than
99% is in the pyranose form
The aldehyde and ketone moieties (parts) of the monosaccharides with 5 and 6 carbons will spontaneously react with
a hydroxyl group present in neighboring carbons to produce intramolecular hemiacetals or hemiketals (respectively)
Hemiacetal or hemiketal formation results in the formation of
5 or 6 membered rings
The 5 membered ring structure resembles the ____, thus sugars with this structure are called __________.
furan
furanoses
Those with 6 membered rings resemble the _______ and are termed _______.
pyran
pyranoses
Pyranoses =
aldohexoses
Furanoses =
fructose ribose
Due to the presence of a free aldehyde or ketone group, carbohydrates are readily _______ and behave as _______ ________.
oxidized , reducing agents
These sugars have the capacity to reduce _____ to ______. Therefore, only the reducing sugars like ____ will give ______ _______.
Cupric ion (Cu 2+) , cuprous ion (Cu+) , glucose, positive reactions
