Biology 1
Unit 2
2. Chemistry: Atoms, Compounds, Water, pH, Organic Molecules, and Enzymes
Matter – anything that has mass and occupies spaces
Atom – the smallest portion of an element
Nucleus – the center part of an atom that contains protons and neutrons
Proton – a particle in an atom found in the nucleus that has a positive electrical charge
Neutron – a particle in an atom found in the nucleus that has no electrical charge
Electron – a particle in an atom that has a negative electrical charge
Element – substance that cannot be separated into a simpler substance; examples: carbon, oxygen, gold
Periodic table – an orderly arrangement of elements based on their atomic numbers
Atomic number – an element’s position in the periodic table based on (and equal to) the number of protons it has in its
nucleus
Isotopes – atoms of the same element that have different numbers of neutrons in the nucleus
Atomic mass – the mass contained in an element’s nucleus, which is equal to the number of protons plus the number of
neutrons
Electron energy level – the distance at which electrons travel around the nucleus of an atom
Chemical compound – a chemical combination of two or more atoms or elements
Chemical reaction – process that occurs when one substance is changed into another
Reactivity – an elements ability or tendency to combine with another element
Valence electrons – the electrons found in the outer energy level of an atom
Octet rule – tendency of atoms to gain, lose, or share electrons with other atoms in order to have 8 electrons in their outer
energy level
Chemical bond – the attractive force between atoms that is formed when atoms transfer or share their electrons
Electron dot diagram – a diagram of an atom that represents its valence electrons as dots around the chemical symbol
Chemical bond – a connection made between atoms when electrons are attracted, shared, or transferred
Ionic bond – a bond formed when elements transfer (gain or lose) electrons
Covalent bond – a bond formed when elements share electrons
Organic compound – carbon-containing compounds that make up living tissue
Polar molecule – a molecule that has a partial positive charge on one end and a partial negative charge on the other end
Hydrogen bond – in the case of water molecules, the weak bond that occurs when the hydrogen in one water molecule is
attracted to the oxygen in another water molecule
Cohesion – the attraction between molecules of the same kind
Surface tension – the film-like quality on the surface of a liquid that is caused by the attraction of the liquid molecules to
themselves
Biology 1
Adhesion – the attraction of one type of molecule to a different type of molecule
Capillary action – the tendency of a liquid to draw up into a narrow tube due to the liquid’s properties of cohesion and
adhesion
Specific heat – the amount of heat needed to raise the temperature of one gram of a substance one degree Celsius
Solvent – a substance that dissolves another
Ion – an atoms or molecules that has gained or lost electrons so that it has a positive or negative charge
Biological process – any process that occurs in a living organisms, such as muscle movement in animals or photosynthesis in
plants
pH – a measure of the acidity or alkalinity of a substance
Acid – a solution with more hydrogen ions than hydroxide ions; having a pH less than 7
Base – a solution with more hydroxide ions than hydrogen ions: having a pH greater than 7
Buffer – a substance that prevents the pH of a solution from changing even if a small amount of an acid or a base is added
Organic compounds – chemical compounds that contain carbon and that make up living organisms
Valence electrons – electrons that can be gained, lost, or shared in a chemical reaction
Macromolecules (or macronutrients) – the large molecules that make up living organisms, such as proteins, carbohydrates,
lipids, and nucleic acids
Monomer – a small molecule that may be chemically bonded to other like molecules to form a polymer
Polymerization – chemical process of combining monomers to forma polymer
Polymer – long chain monomers (small, repeating molecules)
Carbohydrate – an organic molecule made up carbon, hydrogen, and oxygen; used as a source of energy and gives structure
to some types of cells
Monosaccharide – simple sugar
Polysaccharides – a polymer of sugar, meaning a long chain of sugar molecules chemically linked together
Starch – a polysaccharide made by plants to store energy
Cellulose – a polysaccharide used in the cell walls of plants to give cells structural support
Glycogen – a polysaccharide made by animal cells to store energy short term
Lipids – organic molecules made up of carbon, hydrogen, and oxygen, but unlike carbohydrates, they will not dissolve in water
Fat – a type of lipid used to store energy and as a source of fatty acids
Saturated fat – a fat that has all single carbon-to-carbon bonds and the maximum number of hydrogen attached to each
carbon
Monounsaturated fat – a fat that has one double carbon-to-carbon bond
Polyunsaturated fat – a fat that has more than one double carbon-to-carbon bond
Essential fatty acids – fatty acids that cannot be produced by the body but must be eaten; omega 3 and omega 6 fatty acids
are essential fatty acids for humans
Biology 1
Phospholipid – a type of lipid that helps to make up cell membranes
Steroid – a type of lipid that can be present in cell membranes or can make up certain hormones
Steroid – a type of lipid that can be present in cell membranes or can make up certain hormones
Cholesterol – a type of steroid used in cell membranes and also use to make steroid hormones
Wax – a type of lipid that is used to waterproof leaves, skin, feathers, ect.
Protein – an organic molecule with many important functions; the main structural component of muscle, skin, bone, ect.
Amino acids – organic molecules that are building blocks of proteins
Nitrogen – an element found in amino acids and proteins but is NOT found in carbohydrates or fats
Peptide bond – the covalent bond between the amino acids in a protein.
Nucleic acid – an organic molecule that contains carbon, hydrogen, oxygen, nitrogen, and phosphorus and makes up RNA
and DNA
Nucleotide – a molecule that contains a sugar, a phosphate group, and a nitrogen base and that links together to form RNA
and DNA
Deoxyribonucleic acid (RNA) – a nucleic acid molecule in the shape of a double helix that contains deoxyribose sugar and
that stores genetic information
Ribonucleic acid (RNA) – a nucleic acid molecule that contains ribose sugar
Double helix – the shape; similar to a twisted ladder, of a DNA molecule
Enzyme – a biological catalyst that enables chemical reactions to take place in the body
Substrate – a substance that is changed by an enzyme
Active site – the part of an enzyme that “attaches to” a substrate