Biology Chapter 3 Terms

Front 1

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.

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adenosine triphosphate

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The individual subunit of which proteins are made, composed of a central carbon atom to which is bonded an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable group of atoms denoted by the letter “R.

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amino acid

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a compound composed of carbon, hydrogen, and oxygen, with the approximate chemical formula includes sugars and starches.

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carbohydrate

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

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cellulose

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

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chitin

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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.

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dehydration synthesis

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to disrupt the secondary and/or tertiary structure of a protein while leaving its amino acid sequence intact. Denatured proteins can no longer perform their biological functions.

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denature

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

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deoxyribonucleic acid

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a carbohydrate formed by the covalent bonding of two monosaccharides.

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disaccharide

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

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disulfide bridge

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

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enzyme

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

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fat (molecular)

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an organic molecule 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).

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fatty acid

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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.

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functional group

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the most common monosaccharide, with the molecular formula most polysaccharides, including cellulose, starch, and glycogen, are made of glucose subunits covalently bonded together.

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glucose

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

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glycerol

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

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glycogen

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a coiled, springlike secondary structure of a protein.

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helix

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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 a hydroxyl group to the atom on the other side; the reverse of dehydration synthesis.

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hydrolysis

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describing any molecule that does not contain both carbon and hydrogen.

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inorganic

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

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lactose

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one of a number of organic molecules containing large nonpolar regions composed solely of carbon and hydrogen, which make lipids hydrophobic and insoluble in water; includes oils, fats, waxes, phospholipids, and steroids.

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lipid

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a disaccharide composed of two glucose molecules.

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maltose

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

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monomer

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

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monosaccharide

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

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nucleic acid

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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). Nucleotides are linked together, forming a strand of nucleic acid, as follows: Nucleotides are linked together, forming a strand of nucleic acid, by bonds between the phosphate of one nucleotide and the sugar of the next nucleotide.

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nucleotide

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

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oil

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describing a molecule that contains both carbon and hydrogen.

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organic/organic molecule

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

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peptide

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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.

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peptide bond

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a lipid consisting of glycerol bonded to two fatty acids and one phosphate group, which bears another group of atoms, typically charged and containing nitrogen. A double layer of phospholipids is a component of all cellular membranes.

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phospholipid

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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.

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pleated sheet

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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).

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polymer

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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.

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polysaccharide

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the amino acid sequence of a protein.

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primary structure

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polymer of amino acids joined by peptide bonds.

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protein

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fourth level of a protein

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quaternary structure

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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; involved in converting the information in DNA into protein; also the genetic material of some viruses.

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ribonucleic acid

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

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saturated

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

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secondary structure

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

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starch

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a lipid consisting of four fused carbon rings, with various functional groups attached.

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steroid

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a disaccharide composed of glucose and fructose.

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sucrose

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

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sugar

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the complex three-dimensional structure of a single peptide chain; held in place by disulfide bonds between cysteines.

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tertiary structure

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

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triglyceride

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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.

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unsaturated

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

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wax