Macromolecules and Properties of Water

Vocabulary practice flashcards covering the chemical properties of water and the structure, bonds, and functions of biological macromolecules.

Cohesion

Hydrogen bonds that hold one substance together; in water, hydrogen bonds between water molecules allow plants to transport water upward to facilitate photosynthesis.

Adhesion

The clinging of one substance to another, such as hydrogen bonding between water molecules and cell walls, which counters the downward pull of gravity in capillary action.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid, caused by the asymmetry of attraction and ordered arrangement of molecules at the air-water interface.

Specific Heat

The amount of energy required to change $1\text{ gram}$ of a substance by $1^\circ\text{C}$; water's high specific heat prevents large fluctuations in temperature and stabilizes ocean environments.

Heat of Vaporization

The quantity of heat a liquid must absorb for $1\text{ gram}$ of water to be converted to gas at a fixed temperature, enabling evaporative cooling and moderating Earth's climate.

Evaporative Cooling

A temperature-moderating process where the hottest water molecules escape as gas through evaporation, stabilizing temperature and preventing organisms from overheating.

Hydration Shell

The sphere of water ($\text{H}_2\text{O}$) molecules surrounding each dissolved ion in an aqueous solution.

Miller-Urey Project

An experiment showing that complex organic molecules can arise spontaneously under conditions that existed on early Earth (abiotic synthesis) using a closed system that produced macromolecules.

Dehydration Synthesis

A chemical reaction in which two monomers are covalently joined together by releasing a water molecule ($\text{H}_2\text{O}$), with one monomer losing a hydroxyl group ($\text{-OH}$) and the other losing a hydrogen ($\text{H}$).

Hydrolysis

A chemical process that breaks the covalent bond between monomers through the addition of a water molecule ($\text{H}_2\text{O}$), where a hydrogen and a hydroxyl group are attached.

Hydroxyl Group

A polar chemical group consisting of a hydrogen atom covalently bonded to an oxygen atom ($\text{-OH}$); found in alcohols and glycerol.

Carbonyl Group

A functional group with a carbon atom double-bonded to an oxygen atom ($\text{-C=O}$); classified as a ketone when located within the carbon skeleton or an aldehyde when at the end.

Carboxyl Group

A polar chemical group ($\text{-COOH}$) that acts as an acid by donating an $\text{H}^+$ ion to become negatively ionized; characteristic of carboxylic acids.

Amino Group

A polar functional group ($\text{-NH}_2$) with an $\text{N-H}$ bond that acts as a base by accepting an $\text{H}^+$ ion to become positively ionized; characteristic of amines.

Sulfhydryl Group

A chemical group ($\text{-SH}$) that can link with another of the same group to form strong covalent disulfide bridges, stabilizing protein structure.

Phosphate Group

A polar, negatively charged functional group ($\text{-OPO}_3^{2-}$) that reacts with water to release energy when detached in $\text{ATP} \rightarrow \text{ADP}$ and forms the backbone of nucleic acids.

Methyl Group

A nonpolar, hydrophobic chemical group ($\text{-CH}_3$) that affects gene expression as well as the shape and function of sex hormones.

Monosaccharide

A simple sugar with a $1\text{ carbon} : 2\text{ hydrogen} : 1\text{ oxygen}$ ratio; examples include glucose, galactose, fructose, and ribose ($5\text{-carbon}$ sugar).

Glycosidic Linkage

The covalent bond formed between two monosaccharides through a dehydration synthesis reaction.

Starch

A slightly branched plant storage polysaccharide composed of monomers linked together to store excess sugar, which is broken down by hydrolysis.

Glycogen

A highly branched glucose storage polymer in animals synthesized and stored in the liver (and used in muscles), where branching creates extra surface area for hydrolysis to release glucose.

Cellulose

A structural plant polysaccharide composed of glucose chains with $1-4$ linkages grouped into parallel microfibrils; humans cannot digest this fiber, which helps eliminate solid waste.

Chitin

A nitrogen-containing structural polysaccharide that forms the hard protective exoskeleton around soft body parts of insects, spiders, and crustaceans.

Ester Linkage

The covalent bond formed in lipids between the hydroxyl group of glycerol and the carboxyl group of a fatty acid.

Saturated Fats

Lipids with no double bonds between carbon atoms, leaving all bonds filled with hydrogen; they pack tightly together, are solid at room temperature, and contribute to arterial plaque.

Unsaturated Fats

Lipids containing one or more double bonds in their fatty acid chains (fewer hydrogen atoms) that cause bends; they are liquid at room temperature (oils).

Phospholipids

Amphipathic molecules composed of glycerol attached to two hydrophobic fatty acid tails and a third hydroxyl joined to a hydrophilic, negatively charged phosphate group; they form membrane bilayers.

Steroids

Lipids characterized by a carbon skeleton of four fused rings; includes hormones and cholesterol, which is synthesized by the liver and aids in cell membrane formation.

Peptide Bond

The covalent bond formed between the amino group ($\text{-NH}_2$) of one amino acid and the carboxyl group ($\text{-COOH}$) of an adjacent amino acid.

Phosphodiester Bond

The covalent bond that links adjacent nucleotides between the phosphate group and the $5\text{-carbon}$ pentose sugar to form the backbone of a nucleic acid chain.