Chapter 2: The Chemical Level of Organization

adenine

A nitrogen- containing base: ________, cytosine, guanine, thymine, or uracil.

Galactose

Five monosaccharides are important in the body: Glucose, Fructose, ________, Deoxyribose, Ribose.

valence shell

If the ________ is not full, the atom is reactive; meaning it will tend to react with other atoms in ways that make the ________ full.

dehydrationsynthesis

They are involved in ________ and hydrolysis reactions.

Warm core blood

________ cools the surroundings in skin blood vessels.

organic compound

A(n) ________, then, is a substance that contains both carbon and hydrogen.

**elemen**t

is a pure substance that is distinguished from all other matter by the fact that it cannot be created or broken down by ordinary chemical means.

**compound**

is a substance composed of two or more elements joined by chemical bonds.

**atom**

is the smallest quantity of an element that retains the unique properties of that element.

**Atomic number**

which is the number of protons in the nucleus of the atom, identifies the element.

It is always composed of the same three elements

carbon, hydrogen, and oxygen

Atoms are made up of even smaller subatomic particles, three types of which are important

the proton, neutron, and electron

Two types of chemical reactions involve the creation or the consumption of water

dehydration synthesis and hydrolysis

Five monosaccharides are important in the body

Glucose, Fructose, Galactose, Deoxyribose, Ribose

Disaccharides (di

= "two") are made up of two monomers

A pentose sugar

either deoxyribose or ribose

A nitrogen-containing base

adenine, cytosine, guanine, thymine, or uracil

**Mass number**

**i**s the sum of the number of protons and neutrons in its nucleus

**Periodic table of the elements**

is a chart identifying the 92 elements found in nature, as well as several larger, unstable elements discovered experimentally.

**isotope**

is one of the different forms of an element, distinguished from one another by different numbers of neutrons.

**radioactive isotope**

is an isotope whose nucleus readily decays, giving off subatomic particles and electromagnetic energy. 

**electron shel**l

is a layer of electrons that encircle the nucleus at a distinct energy level.

**valence shell**

is an atom’s outermost electron shell.

**bond**

is a weak or strong electrical attraction that holds atoms in the same vicinity.

**molecule**

A more or less stable grouping of two or more atoms held together by chemical bonds is called a

c**hemical compound**

When a molecule is made up of two or more atoms of different elements, it is called a

**ion**

An atom that has an electrical charge—whether positive or negative—is an

**cation**

A positively charged ion is known as a

**anion**

A negatively charged ion is known as an

**ionic bond**

is an ongoing, close association between ions of opposite charg

**hydrogen bond**

is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another molecule.

**kinetic energy**

is the form of energy powering any type of matter in motion.

**Potential energy**

is the energy of position, or the energy matter possesses because of the positioning or structure of its components.

**Chemical energy**

is the form of potential energy in which energy is stored in chemical bonds.

**product**

The one or more substances produced by a chemical reaction are called the

**synthesis reaction**

is a chemical reaction that results in the synthesis (joining) of components that were formerly separate.

**decomposition reaction**

is a chemical reaction that breaks down or “de-composes” something larger into its constituent parts.

**exchange reaction**

is a chemical reaction in which both synthesis and decomposition occur, chemical bonds are both formed and broken, and chemical energy is absorbed, stored, and released. 

**catalyst**

is a substance that increases the rate of a chemical reaction without itself undergoing any change. 

**enzyme**

is a catalyst composed of protein or ribonucleic acid (RNA).

**chemical reaction**

activation energy is the “threshold” level of energy needed to break the bonds in the reactants.

**inorganic compound**

is a substance that does not contain both carbon and hydrogen.

**organic compound**

is a substance that contains both carbon and hydrogen.

**mixture**

is a combination of two or more substances, each of which maintains its own chemical identity.

**solute**

A liquid solution consists of a solvent that dissolves a substance called a

**hydrophobic**

Nonpolar molecules, which do not readily dissolve in water, are called

**colloid**

is a mixture that is somewhat like a heavy solution.

**suspension**

is a liquid mixture in which a heavier substance is suspended temporarily in a liquid, but over time, settles out.

**Dehydration synthesis**

is a type of chemical reaction in which two molecules are joined together by the removal of a water molecule.

**Hydrolysis**

is a chemical reaction in which a molecule is broken down into two parts by the addition of a molecule of water.

**acid**

is a substance that releases hydrogen ions (H+) in solution.

**base**

is a substance that releases hydroxyl ions (OH–) in solution, or one that accepts H+ already present in solution.

**buffer**

is a solution of a weak acid and its conjugate base. 

**functional group**

is a group of atoms linked by strong covalent bonds and tending to function in chemical reactions as a single unit.

**carbohydrate**

is a molecule composed of carbon, hydrogen, and oxygen; in most carbohydrates, hydrogen and oxygen are found in the same two-to-one relative proportions they have in water.

**Monosaccharides**

are the monomers of carbohydrates.

**Disaccharides**

(di- = “two”) are made up of two monomers.

**Polysaccharides**

are the polymers, and can consist of hundreds to thousands of monomers.

**Adenosine triphosphate (ATP)**

is composed of a ribose sugar, an adenine base, and three phosphate groups.

**lipid**

is one of a highly diverse group of compounds made up mostly of hydrocarbons

**triglyceride**

is one of the most common dietary lipid groups, and the type found most abundantly in body tissues.

**phospholipid**

is a bond between the glycerol component of a lipid and a phosphorus molecule.

**steroid**

compound (referred to as a sterol) has as its foundation a set of four hydrocarbon rings bonded to a variety of other atoms and molecules.

**protein**

is an organic molecule composed of amino acids linked by peptide bonds.

**amino acid**

An **___** is a molecule composed of an amino group and a carboxyl group, together with a variable side chain.

**peptide bond**

A **___** is a covalent bond between two amino acids that forms by dehydration synthesis.

**disulfide bond**

A **__** is a covalent bond between sulfur atoms in a polypeptide.

**Denaturation**

is a change in the structure of a molecule through physical or chemical means.

**substrate**

is a reactant in an enzymatic reaction.

**Deoxyribonucleic acid (DNA)**

is a nucleotide that stores genetic information.

**Ribonucleic acid (RNA**)

is a ribose-containing nucleotide that helps manifest the genetic code as protein.

**purine**

A **___** is a nitrogen-containing molecule with a double ring structure, which accommodates several nitrogen atoms.

**pyramidine**

A **___** is a nitrogen-containing base with a single ring structure.

**Phosphorylation**

is the addition of a phosphate group to an organic compound, in this case, resulting in ATP.