Key Terms

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Key Terms

Key Terms

alpha-helix structure (α-helix): type of secondary structure of proteins formed by folding of the polypeptide into a helix shape with hydrogen bonds stabilizing the structure

amino acid: monomer of a protein; has a central carbon or alpha carbon to which an amino group, a carboxyl group, a hydrogen, and an R group or side chain is attached; the R group is different for all 20 amino acids

beta-pleated sheet (β-pleated): secondary structure found in proteins in which pleats are formed by hydrogen bonding between atoms on the backbone of the polypeptide chain

biological macromolecule: large molecule necessary for life that is built from smaller organic molecules

carbohydrate: biological macromolecule in which the ratio of carbon to hydrogen and to oxygen is 1:2:1; carbohydrates serve as energy sources and structural support in cells and form the a cellular exoskeleton of arthropods

cellulose: polysaccharide that makes up the cell wall of plants; provides structural support to the cell

chaperone: (also, chaperonin) protein that helps nascent protein in the folding process

chitin: type of carbohydrate that forms the outer skeleton of all arthropods that include crustaceans and insects; it also forms the cell walls of fungi

dehydration synthesis: (also, condensation) reaction that links monomer molecules together, releasing a molecule of water for each bond formed

denaturation: loss of shape in a protein as a result of changes in temperature, pH, or exposure to chemicals

deoxyribonucleic acid (DNA): double-helical molecule that carries the hereditary information of the cell

disaccharide: two sugar monomers that are linked together by a glycosidic bond

enzyme: catalyst in a biochemical reaction that is usually a complex or conjugated protein

glycogen: storage carbohydrate in animals

glycosidic bond: bond formed by a dehydration reaction between two monosaccharides with the elimination of a water molecule

hormone: chemical signaling molecule, usually protein or steroid, secreted by endocrine cells that act to control or regulate specific physiological processes

hydrolysis: reaction causes breakdown of larger molecules into smaller molecules with the utilization of water

lipid: macromolecule that is nonpolar and insoluble in water

messenger RNA (mRNA): RNA that carries information from DNA to ribosomes during protein synthesis

monomer: smallest unit of larger molecules called polymers

monosaccharide: single unit or monomer of carbohydrates

nucleic acid: biological macromolecule that carries the genetic blueprint of a cell and carries instructions for the functioning of the cell

nucleotide: monomer of nucleic acids; contains a pentose sugar, one or more phosphate groups, and a nitrogenous base

omega fat: type of polyunsaturated fat that is required by the body; the numbering of the carbon omega starts from the methyl end or the end that is farthest from the carboxylic end

peptide bond: bond formed between two amino acids by a dehydration reaction

phosphodiester: linkage covalent chemical bond that holds together the polynucleotide chains with a phosphate group linking two pentose sugars of neighboring nucleotides

phospholipid: major constituent of the membranes; composed of two fatty acids and a phosphate-containing group attached to a glycerol backbone

polymer: chain of monomer residues that is linked by covalent bonds; polymerization is the process of polymer formation from monomers by condensation

polynucleotide: long chain of nucleotides

polypeptide: long chain of amino acids linked by peptide bonds

polysaccharide: long chain of monosaccharides; may be branched or unbranched

primary structure: linear sequence of amino acids in a protein

protein: biological macromolecule composed of one or more chains of amino acids

purine: type of nitrogenous base in DNA and RNA; adenine and guanine are purines

pyrimidine: type of nitrogenous base in DNA and RNA; cytosine, thymine, and uracil are pyrimidines

quaternary structure: association of discrete polypeptide subunits in a protein

ribonucleic acid (RNA): single-stranded, often internally base paired, molecule that is involved in protein synthesis

ribosomal RNA (rRNA): RNA that ensures the proper alignment of the mRNA and the ribosomes during protein synthesis and catalyzes the formation of the peptide linkage

saturated fatty acid: long-chain of hydrocarbon with single covalent bonds in the carbon chain; the number of hydrogen atoms attached to the carbon skeleton is maximized

secondary structure: regular structure formed by proteins by intramolecular hydrogen bonding between the oxygen atom of one amino acid residue and the hydrogen attached to the nitrogen atom of another amino acid residue

starch: storage carbohydrate in plants

steroid: type of lipid composed of four fused hydrocarbon rings forming a planar structure

tertiary structure: three-dimensional conformation of a protein, including interactions between secondary structural elements; formed from interactions between amino acid side chains

trans fat: fat formed artificially by hydrogenating oils, leading to a different arrangement of double bond(s) than those found in naturally occurring lipids

transcription: process through which messenger RNA forms on a template of DNA

transfer RNA (tRNA): RNA that carries activated amino acids to the site of protein synthesis on the ribosome

translation: process through which RNA directs the formation of protein

triacylglycerol (also, triglyceride): fat molecule; consists of three fatty acids linked to a glycerol molecule

unsaturated fatty acid: long-chain hydrocarbon that has one or more double bonds in the hydrocarbon chain

wax: lipid made of a long-chain fatty acid that is esterified to a long-chain alcohol; serves as a protective coating on some feathers, aquatic mammal fur, and leaves