1.3.7: Key Terms

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

beta-pleated sheet (β-pleated)

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 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 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, releasing a water molecule for each bond formed

denaturation

loss of shape in a protein as a result of changes in temperature, pH, or chemical 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 formed by a dehydration reaction between two monosaccharides with eliminating 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 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 protein 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 fat

type of polyunsaturated fat that the body requires; 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

phosphodiester

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

phospholipid

membranes' major constituent; comprised of two fatty acids and a phosphate-containing group attached to a glycerol backbone

polymer

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

polynucleotide

long chain of nucleotides

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 involved in protein synthesis

ribosomal RNA (rRNA)

RNA that ensures the proper alignment of the mRNA and the ribosomes 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 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 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 protein's formation

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 comprised 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