2: Water and Carbon: The Chemical Basis of Life Flashcards
chemical evolution
The theory that simple chemical compounds in the early atmosphere and ocean combined via chemical reactions to form larger, more complex substances, eventually leading to the origin or life and the start of biological evolution.
element
A substance, consisting of atoms with a specific number of protons. Elements preserve their identity in chemical reactions.
atomic number
The number of protons in the nucleus of an atom, giving the atom its identity as a particular chemical element.
mass number
The total number of protons and neutrons in an atom.
isotopes
Any of several forms of an element that have the same number of protons but differ in the number of neutrons.
atomic weight
The average mass of an element that is based on the relative proportions of all the naturally occurring isotopes.
radioactive isotope
A version of an element that has an unstable nucleus, which will release radiation energy as it decays to a more stable form. Decay often results in the radioisotope becoming a different element.
dalton
(Da) A unit of mass equal to 1/12 the mass of one carbon-12 atom; about the mass of 1 proton or 1 neutron.
orbitals
The region of space around an atomic nucleus in which an electron is present most of the time. Each orbitals can hold up to two electrons.
electron shells
A group of orbitals of electrons with similar energies. Electron shells are arranged in roughly concentric layers around the nucleus of an atom, and electrons in outer shells have more energy than those in inner shells. Electrons in the outermost shell, the valence shell, often are involved in chemical bonding.
valence shell
The outermost electron shell of an atom.
valence electrons
An electron in the outermost electron shell, the valence shell, of an atom. Valence electrons tend to be involved in chemical bonding.
valence
The number of unpaired electrons in the outermost electron shell of an atom; often determines how many covalent bonds the atom can form.
chemical bonds
An attractive force binding two atoms together. Covalent bonds, ionic bonds, and hydrogen bonds are types of chemical bonds.
covalent bond
A type of chemical bond in which two atoms share one or more pairs of electrons.
chemical reaction
Any process in which one compound or element is combined with others or is broken down; involves the making and/or breaking of chemical bonds.
molecules
A combination of two or more atoms held together by covalent bonds.
nonpolar covalent bond
A covalent bond in which electrons are equally shared between two atoms of the same or similar electronegativity.
polar covalent bond
A covalent bond in which electrons are shared unequally between atoms differing in electronegativity, resulting in the more electronegative atom having a partial negative charge and the other atom, a partial positive charge.
ion
An atom or a molecule that has lost or gained electrons and thus carries an electric charge, either positive(cation) or negative (anion), respectively.
cation
A positively charged ion.
anion
A negatively charged ion.
molecular formulas
A notation that indicates only the numbers and types of atoms in a molecule, such as H2O for the water molecule.
structural formulas
A two-dimensional notation in which the chemical symbols for the constituent atoms are joined by straight lines representing single, double, or triple covalent bonds.
ball-and-stick models
A representation of a molecule where atoms are shown as balls – colored and scaled to indicate the atom’s identity – and covalent bonds are shown as rods or sticks connecting the balls in the correct geometry.
space filling models
A representation of a molecule where atoms are shown as balls – color-coded and scaled to indicate the atom’s identify–attached to each other in the correct geometry.
electronegativity
A measure of the ability of an atom to attract electrons toward itself from an atom to which it is bonded. Left to right, increase in electronegativity. Top to bottom, decrease in electronegativity.
solvent
Any liquid in which one or more solids or gasses can dissolve.
solution
A liquid containing one or more dissolved solids or gases in a homogeneous mixture.
solutes
Any substance that is dissolved in a liquid.
hydrogen bond
A weak interaction between two molecules or different parts of the same molecule resulting from the attraction between a hydrogen atom with a partial positive charge and another atom (usually O or N) with a partial negative charge.
hydrophilic
Interacting readily with water. Hydrophilic compounds are typically polar compounds containing partially or fully charged atoms.
hydrophobic
Not readily interacting with water. Hydrophobic compounds are typically non polar compounds that lack partially or fully charged atoms.
hydrophobic interactions
Very weak interactions between nonpolar molecules, or nonpolar regions of the same molecule, when exposed to an aqueous solvent. The surrounding water molecules support these interactions with one another and encapsulating the nonpolar molecules.
cohesion
The tendency of certain like molecules (e.g., water molecules) to cling together due to attractive forces.
adhesion
The tendency of certain dissimilar molecules to cling together due to attractive forces.
surface tension
The cohesive force that causes molecules at the surface of a liquid to stick together, thereby resisting deformation of the liquid’s surface and minimizing its surface area.
specific heat
The amount of energy required to raise the temperature of 1 gram of a substance by 1 degree C; a measure of the capacity of a substance to absorb energy.
heat of vaporization
The energy required to vaporize 1 gram of a liquid into a gas.
hydrogen ion
(H+) A single proton with a charge of 1+; typically, one that is dissolved in solution or that is being transferred from one atom to another in a chemical reaction.
hydroxide ion
(OH-) An oxygen atom and a hydrogen atom joined by a single covalent bond and carrying a negative charge; formed by dissociation of water.
acids
Any compound that gives up protons or accepts electrons during a chemical reaction or that releases hydrogen ions when dissolved in water.
bases
Any compound the acquires protons or gives up electrons during a chemical reaction or accepts hydrogen ions when dissolved in water.
mole
the amount of a substance that contains 6.022E23 of its elemental entities(e.g., atoms, ions, or molecules). This number of molecules of a compound will have a mass equal to the molecular weight of that compound expressed in grams.
molecular weight
The sum of the atomic weights of all job the atoms in a molecule; roughly, the total number of protons and neutrons in the molecule.
molarity
A common unit of solute concentration equal to the number of moles of a dissolved solute in 1 liter of solution.
pH
A measure of the concentration of protons in a solution and thus of acidity or alkalinity. Defined as the negative of the base-10 logarithm of the proton concentration: pH = -log[H+].
buffers
A substance that, in solution, acts to minimize changes in the pH of that solution when acid or base is added.
homeostasis
(adjective: homeostatic) The array of relatively stable chemical and physical conditions in an animal’s cells, tissues, and organs. May be achieved by the body’s passively matching the conditions of a stable external environment (conformational homeostasis) or by active physiological processes (regulatory homeostasis) triggered by variations in the external or internal environment.
reactant
Any of the starting materials in a chemical reaction.
product
Any of the final materials formed in a chemical reaction.
chemical equilibrium
A dynamic but stable state of a reversible chemical reaction in which the forward reaction and reverse reactions proceed at the same rate, so that the concentrations of reactants and products remain constant.
endothermic
Referring to a chemical reaction that absorbs heat.
exothermic
Referring to a chemical reaction that releases heat.
energy
The capacity to do work or to supply heat. May be stored (potential energy) or available in the form of motion (kinetic energy).
potential energy
Energy stored in matter as a result of its position or molecular arrangement.
chemical energy
The potential energy stored in covalent bonds between atoms.
kinetic energy
The energy of motion.
thermal energy
The kinetic energy of molecular motion.
temperature
A measurement of thermal energy present in an object or substance, reflecting how much the constituent molecules are moving.
heat
Thermal energy that is transferred from an object at higher temperature to one at lower temperature.
first law of thermodynamics
The principle of physics that energy is conserved in any process. Energy can be transferred and converted into different forms, but it cannot be created or destroyed.
entropy
(S) A quantitative measure of the amount of disorder of any system, such as a group of molecules.
second law of thermodynamics
The principle of physics that the entropy of the universe or any closed system always increases.
LUCA
The last universal common ancestor of cells. This theoretical entity is proposed to be the product of chemical evolution and provided characteristics of life that are shared by all living organisms on Earth today.
prebiotic soup model
Hypothetical explanation for chemical evolution whereby small molecules reacted with one another in a mixture of organic molecules condensed into a body of water, typically in reference to the early oceans.
surface metabolism model
Hypothetical explanation for chemical evolution whereby small molecules reacted with one another through catalytic activity associated with a surface, such as the mineral deposits found in deep-sea hydrothermal vents.
photons
A discrete packet of light energy; a particle of light.
free radicals
Any substance containing one or more atoms with an unpaired electron. Unstable and highly reactive.
functional groups
A small group of atoms bonded together in a precise configuration and exhibiting particular chemical properties that it imparts to any organic molecule in which it occurs.
