Water Properties and Carbohydrates Chemistry

Vocabulary flashcards reviewing the physical properties of water, solution behaviors, carbohydrate structures, monosaccharide stereochemistry, glycosidic bond dynamics, disaccharides, oligosaccharides, and polysaccharides.

Physical Property

A characteristic that can be observed or measured without changing the composition or identity of a substance, acting as a direct manifestation of a physical transformation.

Surface Tension of Water

The energy required to increase the surface area of a liquid by one unit, measuring $72.8\,mj/m^2$ for water, which enables certain insects to move on top of the water surface.

Capillarity

The movement of liquid in a narrow tube resulting from cohesion forces (attraction between liquid molecules) and adhesion forces (attraction between liquid molecules and the tube surface); in water, adhesion forces are greater than cohesion forces.

Density of Water

A physical property that increases as temperature decreases down to approximately $4^\circ C$, where it equals $1000\,kg/m^3$ ($1\,g/cm^3$); below $4^\circ C$, water expands during solidification, making ice less dense than liquid water.

Hydrophilic Substances

Substances with a strong affinity for water whose functional groups contain electric dipoles that form electrostatic hydrogen bonds with water; examples include glucose, mineral salts, alcohols, and urea.

Hydrophobic Substances

Electrically neutral or apolar (lipophilic) substances containing functional groups repelled by water; examples include lipids, oils, alkanes, and benzene.

Carbohydrates

Biomolecules composed exclusively of carbon, hydrogen, and oxygen with a general ratio of $1:1$ between carbon atoms and water molecules ($C(H_2O)$), chemically classified as polyhydroxyaldehydes or polyhydroxyketones.

Functions of Carbohydrates

Biological roles including immediate energy supply (glucose), energy storage (glycogen, starch), structural support (chitin in arthropod exoskeletons, cellulose in plant cell walls), and genetic information storage (ribose and deoxyribose in nucleotides).

D-glyceraldehyde and L-glyceraldehyde

The two optical isomers (enantiomers) of the simple triose glyceraldehyde, distinguished by having the $-OH$ group on the right (D-glyceraldehyde) or left (L-glyceraldehyde) of its chiral center.

Monosaccharide Classification by Carbon Count

Categorization of simple sugars into trioses ($3$ carbons), tetroses ($4$ carbons), pentoses ($5$ carbons), and hexoses ($6$ carbons).

Ribose and Deoxyribose

Biological pentoses forming the nucleotide backbones of RNA ($C_5H_{10}O_5$) and DNA ($C_5H_{10}O_4$) respectively, with deoxyribose containing one less oxygen atom than ribose.

Biological Hexoses

Six-carbon monosaccharides including glucose (primary energy source of the human body), fructose (sugar in fruit and honey), and galactose (found in milk).

Galactose

A hexose monosaccharide present in milk that acts as a C-4 epimer of glucose.

Cyclic Forms of Monosaccharides

Ring structures formed in aqueous solution by the interaction of the carbonyl group with an alcohol group (e.g., glucopyranose formed by carbons 1 and 5 of glucose).

Anomeric Carbon

The carbon atom located at position 1 in the cyclic form of a sugar molecule.

$\alpha$ Anomer vs. $\beta$ Anomer

Sugar ring configurations where the $-OH$ group at the anomeric carbon is oriented downwards relative to the molecular plane in the less stable $\alpha$ form, or upwards in the more stable $\beta$ form.

Glycosidic Bond

A covalent bond formed where an oxygen atom acts as a bridge connecting two monosaccharide molecules.

Condensation Reaction

The reaction that joins two monosaccharides via a glycosidic bond with the simultaneous release of one water molecule.

Hydrolysis

The cleavage of a glycosidic bond using a water molecule, catalyzed in the human intestine by hydrolytic enzymes such as sucrase and lactase to release free monomers.

Disaccharides

Carbohydrates composed of two monosaccharide units; major examples include sucrose ($\alpha$-glucose + $\beta$-fructose), maltose ($\alpha$-glucose + $\alpha$-glucose), and lactose ($\beta$-glucose + $\beta$-galactose).

Oligosaccharides

Carbohydrates formed by $3$ to $10$ monosaccharide units, including dextrins which consist of $6$ or more glucose molecules derived from starch hydrolysis.

Homopolysaccharides vs. Heteropolysaccharides

Polysaccharides containing $10$ or more monosaccharide units, categorized as homopolysaccharides if composed of identical monomeric units, or heteropolysaccharides if composed of different monomeric units.

Starch

The primary storage polysaccharide of plants (found in cereals and tubers), composed of linear amylose ($\alpha \rightarrow 1\text{-}4$ glycosidic bonds) and branched amylopectin ($\alpha \rightarrow 1\text{-}6$ glycosidic bonds at branch points).

Glycogen

The primary energy storage polysaccharide in animals, composed entirely of glucose monomers in a structure similar to starch but with a higher degree of branching.