BioChem Chapter 10
What are the basic features of monosaccharides? What are the defining features of an aldose vs a ketose, and what are triose, tetrose, pentose, hexoses and heptose sugars?
Monosaccarides are the basic building blocks from which all carbs are constructed. Aldose Monosaccharides have an aldehyde functional group and Ketose Monosaccharides have a ketone group. Triose have 3 C atoms, tetrose have 4 C atoms, pentose have 5 C atoms, hexose have 6 C atoms, and heptose have 7.
. What is a nucleotide sugar, and how are such activated sugars used in the biosynthesis of carbohydrate polymers, glycoproteins and glycolipids?
A nucleotide sugar is something that helps synthesize carbohydrate polymers from monomers.
What do the terms configuration and conformation mean, and how do these terms apply to the three dimensional structure of carbohydrates?
Configuration is the 3D arrangement of substituent groups around a chiral center. This relates to carbs because they are either D or L isomers based on what their substituent arrangement is. Conformation is the different 3D arrangements of a molecule which result from free rotation about C-C single bonds. This relates to carbs because the way they can rotate in space determines some of their properties.
What are the distinguishing features of deoxy-sugars, of sugar phosphates, of sugar acids, sugar alcohols, of amino sugars and of N-acetyl-sugars?
Deoxy sugars lack a hydroxyl group at one of their carbons. Sugar phosphates have at least one covalently bound phosphate residue. Sugar acids have at least one carboxyl group, sugar alcohols have the aldehyde or ketone group replaced by an additional hydroxy group, amino sugars have an amino group substituted for one hydroxyl group same with N-acetyl derivatives.
What is the defining feature of a D- vs L-sugar? What is the definition of enantiomer, and why do most biological compounds exist as only one enantiomer (stereoisomer)? How does the stereospecificity of biological reactions relate to the character of enzyme active sites?
Enatiomers are isomers that are exact mirror images of each other.
What does the term epimer mean, and why are most carbohydrate epimers not also enantiomers? Why do most epimers have different chemical names?
Epimer means monosaccharides that differ in stereochemistry at only one chiral carbon, but not the others. They are generally not mirror images of each other, so they are not enantiomers because one part of the structure is the exact same. They have different chemical names because they are two different chemicals with different chemical reactivities.
What are the characteristics of glycogen, and what is its function in humans? What is the monosaccharide component of glycogen? What two types of O-glycosidic linkages occur in the molecule and what is the percentage of each linkage type. What is the significance of the reducing and non-reducing ends of glycogen?
Glycogen is the human storage polysaccharide. It contains 90% alpha 1-4 linkages and 10% alpha 1-6 linkages. The 1-6 linkages form branch points glycogen. Glycogen has glucose units that form a spiral structure and are digestible by humans.
What are hemiacetals and acetals and by what chemical reactions are they formed from alcohols and aldehydes? What does it mean that monosaccharide anomers have a hemiacetal structure, and why do disaccharides have an acetal structure?
Hemiacetals are an alcohol and an aldehyde group reacted together on the same molecule. This is formed through the cyclization of an aldose. An acetal is formed from the reaction of a second alcohol molecule with a hemiacetal. Disaccharides have an acetal structure because the reaction of two cyclized carbohydrates leads to the formation of an acetal. Monosaccharides are hemiacetals because they consist of only one molecule.
Can you identify the important characteristics of the following compounds? (If they are not explicitly shown in the lecture notes please look them up.)Can you distinguish between these different compounds and describe how they are related to each other? Monosaccharides: Glucose, Fructose, Galactose, Mannose, Ribose, Deoxyribose, N- acetyl-Glucosamine, and N-acetyl-Galactosamine Disaccharides: Maltose, Isomaltose, Lactose, Cellibiose, and Sucrose Polysaccharides: Amylose, Amylopectin, Glycogen, Cellulose
Monosaccharides- made of one sugar monomer, Glucose- simple sugar Fructose- simple sugar, found in many plants, often bonded with glucose to form sucrose Galactose- simple sugar, usually found combined with other sugars Mannose- important in human metabolism Ribose- monosaccharide that is used in RNA Deoxyribose- monosaccharide found in DNA N- acetyl-Glucosamine- monosaccharide derivative of glucose. Amide between glucosamine and acetic acid. Important in bacterial cell wall. N-acetyl Galactosamine- amino sugar derivative of galactose. In humans it is the terminal carb forming the antigen of blood type A Disaccharide- two monomers together to form a carb Maltose-disaccharide made of two glucose units, often used in fermentation, linked with 1-4 bond Isomaltose- isomer of maltose, linked with 1-6 bond Lactose- disaccharide made of glucose and galactose often found in dairy products Cellibiose- disaccharide consisting of two glucose units in beta glycosidic linkage. Obtained from partial hydrolysis of cellulose. Sucrose- nonreducing disaccharide made of glucose and fructose. Polysaccharide- many monomers linked together Amylose- D-glucsoe units bonded by 1-4 glycosidic bonds, helps make up starch Amylopectin- highly branched component of starch, 1-4 glycosidic bonds. Glycogen- storage carb, alpha 1-4 and 1-6 linkages Cellulose- no taste, odorless, found in plant cell walls, not digestible by humans
What do the terms monosaccharide, disaccharide, oligosaccharide and polysaccharide mean?
Monosacharides have one monomer unit. Oligosaccharides have 2-10 units. Disacharides are a specific type of oligosaccharide that have 2 units. Polysaccharides have more than 10 units and up to 1000 or more.
What is the process of mutarotation, and how does this process result in alpha and beta anomers? Why are two monosaccharide anomers actually different chemical compounds with differing chemical and physical properties?
Mutarotation is the equilibration between alpha and beta anomers through the aldehydo (open chain) form. This results in alpha and beta anomers because when the compounds become cyclic they become either alpha or beta anomers. They are two different chemical compounds because of their configuration. Alpha anomers have their anomeric carbon pointing down at position 1. Beta anomers have their anomeric carbon pointing up at position 1.
What is an N-glycosidic bond and in what compounds are these bonds found?
N-glycosidic bonds are bonds where a nitrogen atom of an organic base (purine or pyrimidine) is covalently linked to the anomeric group of ribose or deoxy-ribose. These bonds are usually found between monosaccharides to form oligo and polysaccharides.
What is the role of O-glycosidic bonds in the formation of disaccharides, oligosaccharides and polysaccharides? What is the difference between an alpha and beta glycosidic bond, and what to the numbers designate with respect to O-glycosidic bond structure?
O-Glycosidic bonds link different sugars together to form di,oligo,and polysaccharides. An alpha linkage happens when the linkage from the anomeric carbon radiates in a downward direction and a beta linkage occurs when the linkage from the anomeric carbon radiates in an upward direction. The numbers correlate to the anomeric carbon that the bond is formed on in both of the monomers.
How is the formula 2N used to calculate the number of stereoisomers of a family of sugars with the same chemical formula?
The N number is the number is the number of centers of asymmetry. So the number of stereoisomers possible is 2^N.
What are the characteristics of the chair and boat conformational forms of glucose? What is the difference between an axial and an equatorial hydroxyl group? Why are certain conformational forms of sugars preferred? How is the distribution of conformational forms related to steric hindrance?
The chair and boat conformations have both equatorial and axial positions. An axial group is on the radiates up or down, an equatorial group radiates out toward the midline of the conformation. Certain conformations are preferred because they have lower energy levels than others. The most common conformational form is the one that has the least steric hindrance.
What is the defining characteristic of a reducing sugar? Why are monosaccharides reducing sugars but methylated derivatives (at the anomeric carbon) not reducing sugars? What are the reducing and the non-reducing ends of disaccharides and polysaccharides?
The defining characteristic of a reducing sugar is that it can mutarotate through the open chain form to produce an aldehyde. Monosaccharides are reducing compounds, but methylated derivatives are not because they become locked in acetal structure which does not allow them to mutarotate.
What are the major human blood types, and what kinds of sugar derivatives determine a specific blood type?
The major blood types are A, B, and O. Galactose, Fucose, N-Acetylgalactosamine, and N-Acetylglucosamine are all sugars that Type O- 2 Galactose, 1 Fucose,1 N-Acetylglucosamine Type A- 1 Fucose, 2 Galactose, 1 N-Acetylglucosamine, and 1 N-Acetylgalactosamine Type B- 1 Fucose, 3 galactose, 1 N-Acetylglucosamine
