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
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
polysaccharide that makes up the cell wall of plants; provides structural support to the cell
(also, chaperonin) protein that helps nascent protein in the folding process
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
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
two sugar monomers that are linked together by a glycosidic bond
catalyst in a biochemical reaction that is usually a complex or conjugated protein
storage carbohydrate in animals
glycosidic bond
bond formed by a dehydration reaction between two monosaccharides with the elimination of a water molecule
chemical signaling molecule, usually protein or steroid, secreted by endocrine cells that act to control or regulate specific physiological processes
reaction causes breakdown of larger molecules into smaller molecules with the utilization of water
macromolecule that is nonpolar and insoluble in water
messenger RNA (mRNA)
RNA that carries information from DNA to ribosomes during protein synthesis
smallest unit of larger molecules called polymers
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
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
linkage covalent chemical bond that holds together the polynucleotide chains with a phosphate group linking two pentose sugars of neighboring nucleotides
major constituent of the membranes; composed of two fatty acids and a phosphate-containing group attached to a glycerol backbone
chain of monomer residues that is linked by covalent bonds; polymerization is the process of polymer formation from monomers by condensation
long chain of nucleotides
long chain of amino acids linked by peptide bonds
long chain of monosaccharides; may be branched or unbranched
primary structure
linear sequence of amino acids in a protein
biological macromolecule composed of one or more chains of amino acids
type of nitrogenous base in DNA and RNA; adenine and guanine are purines
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
storage carbohydrate in plants
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
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
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
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