Biology 2 The Molecules Of Cells

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acid

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Molecules tending to raise the hydrogen ion concentration in a solution and to lower its pH numerically

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adenine (A)

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One of four nitrogen-containing bases in nucleotides composing the structure of DNA and RNA

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ADP (adenosine diphosphate)

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Nucleotide with two phosphate groups that can accept another phosphate group and become ATP

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amino acid

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Monomer of a protein; takes its name form the fact that it contains an amino group (-NH2) and an acid group (-COOH)

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atom

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Smallest particle of an element that displays the properties of the element

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atomic mass

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Mass of an atom equal to the number of protons plus the number of neutrons within the nucleus

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atomic number

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Number of protons within the nucleus of an atom

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ATP (adenosine triphosphate)

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Nucleotide with three phosphate groups. The breadtown of this into ADP + P makes energy available for energy-requiring processes in cells

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base

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Molecules tending to lower the hydrogen ion concentration in a solution and raise the pH numerically

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buffer

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Substance or group of substances that tend to resist pH changes in a solution, thus stabilizing its relative acidity and basicity

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calorie

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Amount of heat energy required to raise the temperature of water 1 degree Celsius.

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Carbohydrate

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Class of organic compounds that includes monosaccharides, disaccharides, and polysaccharides

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cellulose

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Polysaccharide that is the major complex carbohydrate in plant cell walls

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compound

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Substance having two or more different elements united chemically in a fixed ratio

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covalent bond

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Chemical bond in which atoms share one pair of electrons

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cytosine (C)

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One of four nitrogen-containing bases in the nucleotides composing the structure of DNA and RNA; pairs with guanine

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dehydration reaction

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Chemical reaction resulting in a covalent bond with the accompanying loss of a water molecule

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denaturation

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Loss of normal shape by an enzyme so that it no longer functions; caused by a less than optimal pH and temperature

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disaccharide

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Sugar that contains two units of a monosaccharide

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DNA (deoxyribonucleic acid)

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Nucleic acid found in cells; the genetic material that specifies protein synthesis in cells

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double helix

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Double spiral; descibes the three-dimensional shape of DNA

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electron

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Subatomic particle that has almost no weight and carries a negative charge; orbits the nucleus of an atom in a shell

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element

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substance that cannot be broken down into substances with diferent properties; composed of only one type of atom

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emulsfication

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Breaking up of fat globules into smaller droplets by the action of bile salts or any other emulsifier

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enzyme

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Organic catalyst, usually a protein, that speeds up a reaction in cells due to its paticular shape

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fat

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Organic molecule that contains glycerol and fatty acids and is found in adipose tissue

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fatty acid

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Molecule that contains a hydrocarbon chain and ends with an acid group

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functional group

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Specific cluster of atoms attached to the carbon skeleton of organic molecules that enters into reactions and behaves in a predictable way

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glucose

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six-carbon sugar that organisms degrade as a source of energy during cellular respiration

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glycogen

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Storage polysaccharide, found in animals, that is composed of glucose molecules joined in a linear fasion but having numerous branches

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guanine (G)

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One of four nitrogen-containing bases in nucleotides composign the structure of DNA and RNA; pairs with cytosine

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hexose

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six-carbon sugar

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hydrogen bond

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Weak bond that arises between slightly positive hydrogen atom of one molecule and a slightly negative atom of another molecule or between parts of the same molecule

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hydrolysis reaction

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Splitting of a compound by the addition of water, with the H+ being incorporated in one fragment and the OH- in the other

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hydrophilic

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Type of molecule that interacts with water by dissolvign in water and/or by forming hydrogen bonds with water molecules

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hydrophobic

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Type of molecule that does not interact with water because it is nonpolar

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inorganic molecule

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Type of molecule that is not derived from a living organism

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ion

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particle that carries a negative or positive charge

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ionic bond

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Chemical bond in which ions are attracted to one another by opposite charges

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isotope

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Atom of the same element having the same atomic number but a different mass number due to the number of neutrons

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lipid

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Organic compound that is insoluble in water; notably fats, oils, and steroids

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matter

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Anything that takes up space and has mass

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molecule

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Union of two or more atoms of the same element; also, the smallest part of a compound that retains the properties of the compound

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monomer

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Small molecule that is a subunit of a polymer

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monosaccharide

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simple sugar; a carbohydrate that cannot be decomposed by hydrolysis

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neutron

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Subatomic particle that has the weight of one atomic mass unit, carries no charge, and is found in the nucleus of an atom

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nucleotide

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Monomer of DNA and RNA consisting of a 5-carbon sugar bonded to a nitrogenous base and a phosphate group

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oil

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Triglyceride, ussually of plant origin, that is composed of glycerol and three fatty acids and is liquid in consistency due to many unsaturated bonds in the hydrocarbon chains of the fatty acids

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organic molecule

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Molecule that always contains carbon and hydrogen, and often contains oxygen as well; these are associated with living things

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pentose

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Five-carbon sugar. Deoxyribose is the _____ sugar found in DNA; ribose is the ______ found in RNA

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peptide bond

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Covalent bond that joins two amino acids

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phospholipid

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Molecule that forms the bilayer of the cell's membranes; has polar, hydrophilic head bonded to two nonpolar, hydrophobic tails

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pH scale

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Measurement scale for hydrogen ion conentration; ranges from 0 (acid) to 14 (basic), with 7 neutral

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polymer

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Macromolecule consisting of covalently bonded monomers

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polypeptide

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Polymer of many amino acids linked by peptide bonds

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polysaccharide

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Polymer made from sugar monomers; starch and glycogen are polymers of glucose and monomers

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protein

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Organic macromolecule composed of one or several polypeptides

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proton

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Positive subatomic particle, located in the nucleus and having a weight of approximately one atomic mass unit

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radioactive isotope

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Unstable form of an atom that spontaneously emits radiation in the form of radioactive particles or radiant energy

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RNA (ribonucleic acid)

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Nucleic acid produced by covalent bonding of nucleotide monomers that contain the sugar ribose; occurs in three forms: messenger RNA, ribosomal RNA, and transfer RNA

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saturated fatty acid

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Molecule that lacks double bonds between carbons of its hydrocarbon chain. The chain bears the maximum number of hydrogens

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solute

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Substance that is dissolved in a solvent, forming a solution

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steroid

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Type of lipid molecule havign a complex of four carbon rings

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starch

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Storage polysaccharide found in plants; composed of glucose molecules joined in a linear fashion with few side chains

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thymine (T)

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One of four nitrogen-containing bases in nucleotides composing the structure of DNA; pairs with adenine (A)

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triglyceride

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Neutral fat composed of glycerol and three fatty acids

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unsaturated fatty acid

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Fatty acid molecule that has one or more double bonds between the atoms of its carbon chain

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uracil (U)

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One of the four nitrogen-containing bases in nucleotides composing the structure of RNA; pairs with adenine