Chapter 5 Vocabulary

Macromolecule

Macromolecule

A giant molecule formed by the joining of smaller molecules, usually by a dehydration reaction.

Polymer

A long molecule consisting of many similar or identical monomers linked together by covalent bonds.

Monomer

The subunit that serves as the building block of a polymer.

Enzyme

A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction.

Dehydration synthesis

A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule.

Hydrolysis

A chemical reaction that breaks bonds between two molecules by the addition of water; functions in disassembly of polymers to monomers.

Monosaccharides

The simplest carbohydrate, active alone or serving as a monomer for polymers. Also called simple sugars, have molecular formulas that are generally some multiple of CH2O.

Disaccharide

A double sugar, consisting of two sugar monomers joined by a glycosidic linkage formed by a dehydration reaction.

Glycosidic linkage

A covalent bond formed between two monosaccharides by a dehydration reaction.

Polysaccharides

A polymer of many monosaccharides, formed by dehydration reactions.

Starch

A storage polysaccharide in plants, consisting entirely of glucose monomers joined by glycosidic linkages.

Glycogen

An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch.

Cellulose

A structural polysaccharide of plant cell walls, consisting of glucose monomers joined by β glycosidic linkages.

Chitin

A structural polysaccharide, consisting of amino sugar monomers, found in many fungal cell walls and in the exoskeletons of all arthropods.

Lipids

Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water.

Fat

A lipid consisting of three fatty acids linked to one glycerol molecule; also called a triacylglycerol or triglyceride.

Fatty acid

A carboxylic acid with a long carbon chain. They vary in length and in the number and location of double bonds.

Saturated fatty acid

A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that are attached to the carbon skeleton.

Unsaturated fatty acid

A fatty acid that has one or more double bonds between carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton.

Phospholipid

A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head. They form bilayers that function as biological membranes.

Steroid

A type of lipid characterized by a carbon skeleton consisting of four fused rings with various chemical groups attached.

Cholesterol

A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as many hormones.

Catalyst

A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.

Polypeptide

A polymer of many amino acids linked together by peptide bonds.

Protein

A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.

Amino acid

An organic molecule possessing both a carboxyl and an amino group. They serve as the monomers of polypeptides.

Trans fat

An unsaturated fat, usually formed artificially during hydrogenation of oils, containing one or more trans double bonds.

Peptide bond

The covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a dehydration reaction.

Primary structure

The level of protein structure referring to the specific linear sequence of amino acids.

Secondary structure

Regions of repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bonding between constituents of the backbone (not the side chains).

Alpha helix

A coiled region constituting one form of the secondary structure of proteins, arising from a specific pattern of hydrogen bonding between atoms of the polypeptide backbone (not the side chains).

Beta pleated sheet

One form of the secondary structure of proteins in which the polypeptide chain folds back and forth.

Tertiary structure

The overall shape of a protein molecule due to interactions of amino acid side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

Hydrophobic interaction

A type of weak chemical interaction caused when molecules that do not mix with water coalesce to exclude water.

Disulfide bridges

A strong covalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer.

Quaternary structure

The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide.

Denaturation

In proteins, a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive.

Chaperonins

A protein complex that assists in the proper folding of other proteins.

Gene

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

Nucleic acids

A polymer consisting of many nucleotide monomers

Deoxyribonucleic acid

A nucleic acid molecule, usually a double-stranded helix, in which each polynucleotide strand consists of nucleotide monomers with a deoxyribose sugar.

Ribonucleic acid

A type of nucleic acid consisting of a polynucleotide made up of nucleotide monomers with a ribose sugar.

Gene expression

The process by which information encoded in DNA directs the synthesis of proteins.

Polynucleotides

A polymer consisting of many nucleotide monomers in a chain.

Nucleotide

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one or more phosphate groups.

Pyrimidine

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring.

Purines

One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring.

Deoxyribose

The sugar component of DNA nucleotides, having one fewer hydroxyl group.

Ribose

The sugar component of RNA nucleotides.

Antiparallel

Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix.

Double helix

The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.

Genomics

The systematic study of whole sets of genes (or other DNA) and their interactions within a species, as well as genome comparisons between species.

Proteomics

The systematic study of sets of proteins and their properties, including their abundance, chemical modifications, and interactions.