BIOL 1001 Chapter 3

Denature

To disrupt the secondary and/or tertiary structure of a protein while leaving its amino acid sequence intact.

Sugar

A simple carbohydrate molecule, either a monosaccharide or a disaccharide.

Disaccharide

A carbohydrate formed by the covalent bonding of two monosaccharides.

Peptide

A chain composed of two or more amino acids linked together by peptide bonds.

Dehydration synthesis

A chemical reaction in which two molecules are joined by a covalent bond with the simultaneous removal of a hydrogen from one molecule and a hydroxyl group from the other, forming water; the reverse of hydrolysis.

Steroid

A class of hormone whose chemical structure (four fused carbon rings with various functionally groups) resembles cholesterol; steroids, which are lipids, are secreted by the ovaries and placenta, the testes, and the adrenal cortex.

Helix

A coiled, springlike secondary structure of a protein.

Carbohydrate

A compound composed of carbon, hydrogen, and oxygen, with the approximate chemical formula (1C, 2H, 1O); includes sugars and starches.

Chitin

A compound found in the cell walls of fungi and the exoskeletons of insects and some other arthropods; composed of chains of nitrogen-cointaining modified glucose molecules.

Sucrose

A disaccharide composed of glucose and fructose.

Lactose

A disaccharide composed of glucose and galactose; found in mammalian milk.

Maltose

A disaccharide composed of two glucose molecules.

Pleated sheet

A form of secondary structure exhibited by certain proteins, such as silk, in which many protein chains lie side-by-side, with hydrogen bonds holding adjacent chains together.

Polysaccharide

A large carbohydrate molecule composed of branched or unbranched chains of repeating monosaccharide subunits, normally glucose or modified glucose molecules; includes starches, cellulose, and glycogen.

Wax

A lipid composed of fatty acids covalently bonded to long-chain alcohols.

Oil

A lipid composed of three fatty acids, some of which are unsaturated, covalently bonded to a molecule of glycerol; liquid at room temperature.

Triglyceride

A lipid composed of three fatty-acid molecules bonded to a single glycerol molecule

Fat

A lipid composed of three saturated fatty acids covalently bonded to glycerol; solid at room temperature.

Phospholipid

A lipid consisting of glycerol bonded to two fatty acids and one phosphate group, which bears another group of atom, typically charged and containing nitrogen.

Glycogen

A long, branched polymer of glucose that is stored by animals in the muscles and liver and metabolized as a source of energy.

Polymer

A molecule composed of three or more (perhaps thousands) smaller subunits called monomers, which may be identical (for example, the glucose monomers of starch) or different (for example, the amino acids of a protein).

Starch

A polysaccharide that is composed of branched or unbranched chains of glucose molecules; used by plants as a carbohydrate-storage molecule.

Enzyme

A protein catalyst that speeds up the rate of specific biological reactions.

Secondary structure

A repeated, regular structure assumed by protein chains held together by hydrogen bonds; for example, a helix.

Monomer

A small organic molecule, several of which may be bonded together to form a chain called a polymer.

Nucleotide

A subunit of which nucleic acids are composed; a phosphate group bonded to a sugar (deoxyribose in DNA), which is in turn bonded to a nitrogen-containing base (adenine, guanine, cytosine, or thymine in DNA).

Glycerol

A three-carbon alcohol to which fatty acids are covalently bonded to make fats and oils.

DNA

Acronym for a molecule composed of deoxyribose nucleotides; contains the genetic information of all living cells.

RNA

Acronym for a molecule composed of ribose nucleotides, each of which consists of a phosphate group, the sugar ribose, and one of the bases adenine, cytosine, guanine, or uracil; transfers hereditary instructions from the nucleus to the cytoplasm; also the genetic material of some viruses.

ATP

Acronym for a molecule composed of the sugar ribose, the base adenine, and three phosphate groups; the major energy carrier in cells. The last two phosphate groups are attached by high-energy bonds.

Cellulose

An insoluble carbohydrate composed of glucose subunits; forms the cell wall of plants.

Nucleic acid

An organic molecule composed of nucleotide subunits the two common types of nucleic acids are ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).

Fatty acid

An organic molecules composed of a long chain of carbon atoms, with a carboxylic acid (COOH) group at one end; may be saturated (all single bonds between the carbon atoms) or unsaturated (one or more double bonds between the carbon atoms).

Organic

Describing a molecule that contains both carbon and hydrogen.

Inorganic

Describing any molecule that does not contain both carbon and hydrogen,

Lipid

One of a number of organic molecules containing large non-polar regions composed solely of carbon and hydrogen, which makes lipids hydrophobic and insoluble in water; includes oils, fats, waxes, phospholipids, and steroids.

Functional group

One of several groups of atoms commonly found in an organic molecule, including hydrogen, hydroxyl, amino, carboxyl, and phosphate groups, that determine the characteristics and chemical reactivity of the molecule.

Protein

Polymer of amino acids joined by peptide bonds.

Saturated

Referring to a fatty acid with as many hydrogen atoms as possibly bonded to the carbon backbone; a fatty acid with no double bonds in its carbon backbone.

Unsaturated

Referring to a fatty acid with fewer than the maximum number of hydrogen atoms bonded to its carbon backbone; a fatty acid with one or more double bonds in its carbon backbone.

Glucose

The most common monosaccharide with the molecular, with the molecular formula C6H12O6.

Primary structure

The amino acid sequence of a protein.

Monosaccharide

The basic molecular unit of all carbohydrates, normally composed of a chain of carbon atoms bonded to hydrogen and hydroxyl groups.

Hydrolysis

The chemical reaction that breaks a covalent bond by means of the addition of hydrogen to the atom on one side of the original bond and hydroxyl group to the atom on the other side; the reverse of dehydration synthesis.

Quaternary structure

The complex three-dimensional structure of a protein composed of more than one peptide chain.

Tertiary structure

The complex three-dimensional structure of a single peptide chain held in place by disulfide bonds between cystines.

Peptide bond

The covalent bond between the amino group's nitrogen of one amino acid and the carboxyl group's carbon of a second amino acid, joining the two amino acids together in a peptide or protein.

Disulfide bond

The covalent bond formed between the sulfur atoms and two cystines in a protein; typically caused the protein to fold by bringing otherwise distant parts of the protein close together.

Amino acid

The individual subunit of which proteins are made, composed of a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable group of atoms denoted by the letter R.