Key Concepts of Biological Macromolecules and Proteins

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 the most common 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

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

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 that causes breakdown of larger molecules into smaller molecules with the utilization of water

lipid

macromolecule that is nonpolar and insoluble in water

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

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…

pyrimidine

type of nitrogenous base in DNA and RNA; cytosine, thymine, and uracil are…

quaternary structure

association of discrete polypeptide subunits in a protein

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

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