BIO CHAPTER 3

alpha-helix structure (α-helix) – type of secondary protein structure formed by folding the

polypeptide into a helix shape with hydrogen bonds stabilizing the structure

amino acid – a protein’s monomer; 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 common amino acids

amphipathic – a molecule with both hydrophobic and hydrophilic parts beta-pleated sheet

β-pleated sheet – secondary structure in proteins in which hydrogen bonding forms “pleats”

between atoms on the polypeptide chain’s backbone

biological macromolecule – large molecule necessary for life that is built from smaller or-

ganic 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 arthropods’ cellular exoskeleton

cellulose – polysaccharide that comprises the plants’ cell wall; 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 fungi cell walls

dehydration synthesis – (also, condensation) reaction that links monomer molecules, re-

leasing a water molecule for each bond formed

denaturation – loss of shape in a protein as a result of changes in temperature, pH, or chem-

ical exposure

deoxyribonucleic acid (DNA) – double-helical molecule that carries the cell’s hereditary

information

disaccharide – two sugar monomers that a glycosidic bond links

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

glycogen – storage carbohydrate in animals

glycosidic bond – bond joining monosaccharides

hormone – chemical signaling molecules that are usually small proteins

hydrolysis – reaction that causes breakdown of larger molecules into smaller molecules by

utilizing water

lipid – macromolecule that is nonpolar and insoluble in water

messenger RNA (mRNA) – RNA that carries information from DNA to ribosomes during pro-

tein synthesis

monomer – smallest unit of larger molecules that are polymers

monosaccharide – single unit or monomer of carbohydrates

nucleic acid – biological macromolecule that carries the cell’s genetic blueprint and carries

instructions for the cell’s functioning

nucleotide – monomer of nucleic acids; contains a pentose sugar, one or more phosphate

groups, and a nitrogenous base

omega fatty acid – type of unsaturated fatty acid, some of which the body requires in the

diet; numbering 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

phospholipid – membranes’ major constituent; comprised of two fatty acids and a phos-

phate-containing group attached to a glycerol backbone

polymer – chain of monomer residues that covalent bonds link; polymerization is the pro-

cess of polymer formation from monomers by condensation

polypeptide – long chain of amino acids that peptide bonds link

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

primary structure – linear sequence of amino acids in a protein

protein – biological macromolecule comprised of one or more amino acid chains

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 in-

volved in protein synthesis

ribosomal RNA (rRNA) – RNA that ensures the proper alignment of the mRNA and the ribo-

somes during protein synthesis and catalyzes, forming the peptide linkage

saturated fatty acid – long-chain 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 that proteins form 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 comprised of four fused hydrocarbon rings forming a planar structure

tertiary structure – a protein’s three-dimensional conformation, including interactions be-

tween secondary structural elements; formed from interactions between amino acid side

chains

transcription – the process by which DNA dictates the structure of RNA

translation – the process by which mRNA dictates the structure of proteins

trans fat – fat formed artificially by hydrogenating oils, leading to a different arrangement of

double bond(s) than those in most naturally occurring lipids

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