Biochemistry - Carbohydrates

functions of heteropolysaccharides

1. serve as parts of structural elements within the cell. 2. increase the solubility of the molecules to which they are attached. They contain many hydroxyl groups that form hydrogen bonds with the water within or outside the cell. 3. act as signal molecules. Many extracellular proteins, proteins secreted by the cell, have heteropolysaccharides covalently attached. When attached to the protein they signal to the cell that the protein is to be secreted. 4. orient molecules correctly in cellular membranes. The attached sugar polymer orients the molecule correctly in the membrane, with the polysaccharide directed extracellularly, toward the outside of the cell. 5. are cellular adhesion molecules. Heteropolysaccharides attached to the outside of cells help to hold cells together in tissues and organs by forming numerous hydrogen bonds with other molecules on adjacent cells. 6. are "markers", are "antigenic determinants". Antigenic determinants are the molecules that must be "matched" before a transfusion or transplant can be attempted. Heteropolysaccharides covalently attached to other biomolecules on the cell surface are a subset of antigenic determinants that must be matched.

The three important homopolysaccharides of glucose

Cellulose, Starch, and Glycogen.

5 important glycosaminoglycans

Chondroitin Sulfate, Dermatin Sulfate, Heparin, Hyaluronic Acid, Keratan Sulfate

general formula for monosaccharide

Cn(H2O)n where n is greater than or equal to 3.

EPIMERS

Compounds with more than one chiral carbon having identical configurations around all of the chiral carbons except for one

examples of epimers

D-glucose and D-galactose; D-glucose & D-mannose; D-ribulose & D-xylulose

GLYCOPROTEIN or a PROTEOGLYCAN, GLYCOLIPIDS

HETEROpolysaccharides are usually covalently linked to proteins. are part of cellular membranes

DEOXY SUGAR

One of more of the hydroxyl groups can be reduced to a hydrogen to form this

AMINO SUGAR

One or more of the hydroxyl groups on the sugar can be substituted for by an amino group (-NH2) to form _____. α-D-2-glucosamine and α-D-2-galactosamine are examples

Amylopectin

a branched polymer of glucose. The backbone of the polymer is maintained by glucose α1 → 4 glucose glycosidic bonds. The branch points of the polymer are glucose α1 → 6 glucose glycosidic bonds occurring every 24 to 30 glucose residues along the backbone.

Amylose

a long linear polymer of glucose. The glucose residues are held together by glucose α1 → 4 glucose glycosidic bonds

DISACCHARIDES

two monosaccharides joined by a covalent bond

SUGAR ALCOHOLS

The aldehyde group and/or ketone group on the monosaccharides can be reduced to an alcohol group to form these

AMIDES

The amino group of amino sugars can react with carboxylic acids to form _____. The carboxylic acid is usually ethanoic acid (acetic acid) to form N-acetyl sugars

URONIC ACID

The cell can oxidize the last hydroxyl group of a monosaccharide to the level of a Carboxylic Acid. When the last -OH group is oxidized, the product is a _____

GLYCOSIDIC BOND

The chemical bond holding disaccharides, oligosaccharides, and/or polysaccharides together is a _____. The anomeric hydroxyl group on one sugar always reacts with a hydroxyl group on a second sugar to form a _____, to form an acetal or ketal functional group. reducing sugar

Cellulose

The linkage between the monomer units in this polymer is glucose β1 → 4 glucose.-->very stable chemical bond, it is resistant to hydrolysis under strongly acidic or strongly basic conditions and is the indigestible material in our diets

esters

The hydroxyl groups can react with carboxylic acids to form this. The most important _____ of monosaccharides are those formed by the reaction with the biological form of phosphoric acid (phosphate) or sulfuric acid (sulfate)

mutarotation

The α-form, the open chain (linear) form, and the β-form are in equilibrium with each other. This equilibrium, this interconversion between the three forms of a monosaccharide in solution

Chondroitin Sulfate

This heteropolysaccharide is composed of D-Glucuronate and Nacetyl-D-galactosamine, sulfated either at position 4 or position 6. As part of a proteoglycan, it is found in tendons, cartilage and bone where it functions to modulate the compressibility of these tissues

ALDONIC ACID

When the aldehyde group of a monosaccharide is oxidized to form Carboxylic Acids _____ is formed

MONOSACCHARIDES

also called the simple sugars. They cannot be broken down (hydrolyzed) into smaller molecules and still retain the structure and properties of a carbohydrate

HOMOPOLYMERS or HOMOPOLYSACCHARIDES

composed of a single type of monosaccharide unit, for example, the polymer can be composed entirely of glucose residues. Much of the plaque that forms on teeth is a homopolymer of fructose

POLYSACCHARIDES / COMPLEX CARBOHYDRATES

contain greater than twenty monosaccharide units covalently linked to one another.

KETOSE

contains a ketone functional group on carbon two.

ALDOSE

contains an aldehyde functional group on carbon one

largest naturally occuring monosaccharide

contains nine carbon atoms

Lactose

galactose β1 → 4 glucose composed of a molecule of galactose covalently linked by a glycosidic bond to a glucose molecule. The anomeric hydroxyl group on carbon 1 of galactose in the β configuration is covalently linked to the hydroxyl group on carbon 4 of the glucose residue. reducing sugar

Maltose

glucose α1 → 4 glucose two molecules of glucose where the hemiacetal hydroxyl group on carbon 1 of the first glucose in the α configuration (the anomeric -OH group) reacts with the -OH group on carbon 4 of the second glucose molecule

Sucrose

glucose α1 → β2 fructose or fructose β2 → α1 glucose composed of glucose covalently linked to fructose. The hemiacetal hydroxyl group in the α configuration on glucose is linked to the hemiketal hydroxyl group in the β configuration on fructose. nonreducing sugar.

GLYCOSAMINOGLYCANS

heteropolysaccharides with repeating saccharide units; the -A-B-A-B- type. One of the repeating units is a monosaccharide modified by the addition of an AMINO SUGAR (glycosamino). The amino sugar is often further modified by the addition of sulfate groups in ester linkage. The other part of the repeating unit is a monosaccharide where the -OH group on carbon 6 has been oxidized to a carboxylic acid (a uronic acid group or a glycan). Usually covalently attached to proteins to form larger molecules called PROTEOGLYCANS

Hyaluronic Acid

is composed of D-Glucuronate and N-acetyl-D-glucosamine. It is found in the synovial fluid surrounding joints where it acts as a lubricant. It is also found in the vitreous humor of the eye, in cartilage, and in loose connective tissue where it modulates fluidity and/or compressibility.

Dermatin Sulfate

is composed of L-Iduronate, a modified L-sugar, and N-acetyl-Dgalactosamine. It is rich in the skin and blood vessels where it modulates elasticity. It is also found in the cornea of the eye where it modulates transparency

Keratan Sulfate

is made up from D-Galactose and N-acetyl-D-glucosamine. It functions to modulate corneal transparency. It is also present in cartilage, tendons and the "dead" tissues of hair, horns, hooves, and claws.

Heparin

is produced by Mast Cells, a type of White Blood Cell, and is composed of D-Glucuronate and D-glucosamine. It acts as an anticoagulant; it prevent blood clotting

OLIGOSACCHARIDES

polymers containing from two to twenty monosaccharide units covalently joined.

HETEROPOLYMERS or HETEROPOLYSACCHARIDES

the polysaccharide can be composed of several different monosaccharides.

Glycogen

the storage form of carbohydrates in animal cells. The backbone structure of the glycogen molecule is glucose α1 → 4 glucose. Structurally, it is very similar to amylopectin in that it is a branched polymer. The branch points are glucose α1 → 6 glucose glycosidic bonds.Glycogen is much more highly branched, it contains a branch every 8 to 12 residues.

Starch

the storage form of carbohydrates in plants cells. actually a mixture of two polymers, Amylose and Amylopectin.

ANOMERS

when an achiral carbon, on a molecule with more than one chiral carbon atoms, chemically reacts to produce a new chiral carbon, two products result. These products have opposite configurations around the new chiral carbon and the two products are ANOMERS of each other