General, Organic and Biological Chemistry - Carbohydrates

Flashcards covering the classification, chemical structure, specific examples, and biological reactions of carbohydrates as detailed in Chapter 18.

Carbohydrates

The most abundant class of bioorganic molecules on earth, produced by the photosynthetic activity of green plants and functioning as a storehouse of chemical energy.

Saccharides

Another name for carbohydrates, derived from the Latin word "saccharum" meaning sugar, due to the sweet taste of many members of the class.

Monosaccharides

Simple sugars that contain a single polyhydroxy aldehyde or polyhydroxy ketone unit and cannot be degraded into simpler products by hydrolysis.

Disaccharides

Carbohydrates that contain 2 monosaccharide units covalently bonded to each other, which produce monosaccharides upon hydrolysis.

Oligosaccharides

Carbohydrates containing 2 to 10 monosaccharide units covalently bonded; they are often found associated with proteins and lipids in complex molecules.

Polysaccharides

Complex carbohydrates consisting of tens of thousands of monosaccharide units covalently bonded together.

Aldose

A monosaccharide that contains an aldehyde functional group.

Ketose

A monosaccharide that contains a ketone functional group, usually indicated by the ending "-ulose" in its name.

Triose

The simplest classification of monosaccharides by carbon count, having the general formula $C_3H_6O_3$.

D-Isomer

A monosaccharide isomer where the $-OH$ group is written to the right of the carbon atom adjacent to the terminal primary alcohol group in a Fischer projection.

L-Isomer

A monosaccharide isomer where the $-OH$ group is written to the left of the carbon atom adjacent to the terminal primary alcohol group in a Fischer projection.

Glucose

The most abundant and nutritionally important monosaccharide in nature, also known as grape sugar, dextrose, or blood sugar ($70-100\,mg/100\,mL$).

Fructose

A ketohexose known as the healthiest dietary sugar and the sweetest of all sugars; commonly called fruit sugar.

Galactose

An aldohexose known as "brain sugar" because it is a component of brain and nerve tissue; it is also a component of milk sugar.

Ribose

An aldopentose that serves as a building block for RNA, DNA, and ATP.

Galactosemia

A genetic deficiency where an infant lacks the enzyme to convert $D\text{-galactose}$ to $D\text{-glucose}$, causing galactose to build up in blood and tissue.

Hemiacetals

Cyclic structures formed from the intramolecular reaction between an aldehyde group and an alcohol group within a sugar molecule.

Pyranose ring

A six-membered cyclic hemiacetal ring structure derived from the parent compound pyran.

Furanose ring

A five-membered cyclic hemiacetal ring structure derived from the parent compound furan.

Anomers

Cyclic monosaccharides that differ only in the position of the substituents on the anomeric carbon atom ($\alpha$ vs $\beta$).

Mutarotation

The process of interconversion between $\alpha$ and $\beta$ anomers in aqueous solution, resulting in a change in specific rotation.

Aldonic acid

An acidic sugar produced when a weak oxidizing agent like Tollens or Benedict's solution oxidizes the aldehyde end of an aldose.

Aldaric acid

An acidic sugar produced when strong oxidizing agents oxidize both ends of a monosaccharide simultaneously.

Sorbitol

A sugar alcohol, also known as glucitol, used as a moisturizing agent in cosmetics and a sweetening agent in chewing gum.

Reducing sugar

A sugar that can donate electrons and reduce silver ions to free silver or copper(II) ions to copper(I) ions; includes all aldoses and some ketoses.

Glycoside

An acetal formed when the hemiacetal carbon $-OH$ group of a cyclic monosaccharide is replaced with an $-OR$ group from an alcohol.

Maltose

A reducing disaccharide consisting of two glucose units linked by an $\alpha\text{-(1}\rightarrow\text{4)-glycosidic bond}$; found in corn syrup and germinating seeds.

Cellobiose

A reducing disaccharide produced from the hydrolysis of cellulose, containing two glucose units linked by a $\beta\text{-(1}\rightarrow\text{4)-glycosidic linkage}$.

Lactose

A reducing disaccharide known as milk sugar, composed of $\beta\text{-galactose}$ and glucose units linked by a $\beta\text{-(1}\rightarrow\text{4)-glycosidic linkage}$.

Sucrose

A nonreducing disaccharide known as common table sugar, composed of an $\alpha\text{-glucose}$ unit and a $\beta\text{-fructose}$ unit linked by an $\alpha, \beta\text{-(1}\rightarrow\text{2)-glycosidic bond}$.

Invert sugar

A mixture of $D\text{-glucose}$ and $D\text{-fructose}$ produced by the hydrolysis of sucrose, which is sweeter than sucrose and less likely to crystallize.

Solanin

A potato toxin consisting of an oligosaccharide associated with an alkaloid, which contributes to the bitter taste of some potatoes.

Amylose

A straight-chain starch polymer ($15-20\%$ of starch) made of $60-300$ glucose units joined by $\alpha\text{-(1}\rightarrow\text{4)-glycosidic bonds}$.

Amylopectin

A branched starch polymer ($80-85\%$ of starch) with branches occurring every $25-30$ units via $\alpha\text{-(1}\rightarrow\text{6)-glucosidic bonds}$.

Glycogen

The animal starch used for glucose storage in liver and muscle cells; it is more highly branched than amylopectin.

Cellulose

A structural polysaccharide in plant cell walls made of glucose units linked by $\beta\text{-(1}\rightarrow\text{4)-glucosidic bonds}$, which humans cannot digest.

Chitin

A structural polysaccharide component of arthropod exoskeletons, consisting of units of $N\text{-acetyl-D-glucosamine}$ bound by $\beta\text{-(1}\rightarrow\text{4)-glycosidic linkages}$.

Hyaluronic acid

An acidic polysaccharide that serves as a lubricant in joint fluid and the vitreous humor of the eye.

Heparin

An acidic polysaccharide found in the blood that acts as an anticoagulant to inhibit blood clot formation.

Glycemic index

A rating system for foods based on how quickly carbohydrates are digested, how high blood glucose rises, and how quickly it returns to normal.

Glycolipid

A lipid molecule covalently bonded to one or more carbohydrate units, important for cell-cell recognition and adhesion.

Unavailable carbohydrates

Carbohydrates that are not hydrolyzed by human digestive enzymes and constitute dietary fiber.