Biochemistry Terms


Amino acid: Building block of proteins and peptides; contains a carbon atom that is covalently bonded to an amino group, a carboxylic acid group, a R group, and a hydrogen atom.


Amphipathic: A molecule that contains both hydrophilic and hydrophobic regions, such as a phospholipid.


Anabolism: Metabolic synthesis reactions that combine small molecules to build larger molecules, usually with the net absorption of energy.


ATP (Adenosine triphosphate): The universal energy carrier; organic molecule that stores and releases chemical energy for use in cells.


Carbohydrate: A major class of biological molecules; contains carbon, hydrogen and oxygen with the general formula Cn (H2O)m ; used as energy stores and structural molecules.


Catabolism: Metabolic decomposition reactions that breakdown large molecules into smaller molecules, usually with the net release of energy.


Cellulose: Polysaccharide made from glucose that cannot be digested by most animals; the major structural component of plants.


Coenzyme: Nonprotein substance associated with an enzyme; usually a vitamin.


Dehydration synthesis reaction: Formation of a large molecule by covalently bonding small molecules together, with the loss of water, H2O. Also called a condensation reaction.


Denaturation: Loss of a molecule's 3-D shape, as weak bonds are disrupted.


Disaccharide: A carbohydrate containing two covalently bonded sugar monomers.


DNA (Deoxyribonucleic acid): Molecule of inheritance; contains instructions for making all proteins required to build and maintain cells; it has a 3-D structure called the DNA double helix, consisting of two backbones with alternating deoxyribose and phosphate groups, and a pair of nitrogenous bases joined by hydrogen bonds.


Enzyme: A biological catalyst that increases the rate of a chemical reaction, but is not consumed.


Fat: Lipid with glycerol bound to three fatty acids; the body's most concentrated source of energy fuel; saturated fats have fatty acid tails that are linear with only C-C single bonds, are solid at room temperature, and are prevalent in animal fat; unsaturated fats have fatty acid tails that are bent due to C=C double bonds, are liquid at room temperature, and are prevalent in plant oils. Also called triglyceride or triacylglycerol.


Fatty acid: Molecule with a backbone of up to 36 carbon atoms, a carboxylic acid group (-COOH) at one end, and hydrogen atoms at the other bonding sites.


Functional group: An atom, or group of atoms, that is covalently bonded to the carbon backbone of an organic compound and influences its chemical behavior.


Glucose: Principal blood sugar with the formula C6H12O6 ; the chief source of energy for living organisms.


Glycogen: A highly branched polysaccharide of glucose monomers; main carbohydrate stored in animals; abundant in liver and muscles.


Glycosidic bond: A covalent bond (-C-O-C-) that links two monosaccharides together.


Hydrocarbon: Organic compound that contains only hydrogen and carbons atoms.


Hydrolysis reaction: Breakdown of a large molecule into small molecules by adding water, H2O.


Hydrophilic: A polar molecule that is very soluble in water (water loving).


Hydrophobic: A nonpolar molecule that is insoluble in water (water fearing).


Lipid: A major class of biological molecules that are hydrophobic or amphipathic; used in cell membranes, as storage forms of energy, as hormones, and as vitamins.


Metabolism: All of the chemical reactions that occur in the body.


Monomer: Small molecule used as the subunits of polymers.


Monosaccharide: Building block of carbohydrates; simple sugar such as glucose, galactose, and fructose.


Nucleic acid: A major class of biological molecules that contain sugars, phosphates, and nitrogenous bases, such as DNA, RNA, and ATP.


Nucleotide: Building block of nucleic acids; contains a five-carbon sugar (ribose or deoxyribose), a phosphate group, and a nitrogenous base.


Oligosaccharide: Short-chain carbohydrate containing several monosaccharides.


Peptide: A polymer of amino acids.


Peptide bond: A covalent bond (-CO-NH-) that joins two amino acids.


Phospholipid: The main structural component of cell membranes; usually contains a glycerol backbone, two fatty acid tails, and a hydrophilic head with a phosphate group and a nitrogenous base.


Polymer: Large molecule formed by joining together many monomers.


Polysaccharide: A polymer of monosaccharides, such as glycogen, starch, and cellulose.


Protein: A major class of biological molecules; contains one or more peptides.


RNA (Ribonucleic acid): Single-stranded nucleic acid that contains ribose, phosphate, and nitrogenous bases; used in protein synthesis.


Starch: A polysaccharide of glucose monomers; the main storage carbohydrate in plants.


Steroid: Lipid with a rigid backbone of four fused carbon rings, such as cholesterol, testosterone and estrogen.


Substrate: The substance that binds to an enzyme then is chemically changed into another substance.


Sucrose: A disaccharide composed of glucose and fructose joined by a glycosidic bond.